nature vs nurture research paper questions

80 Nature vs Nurture Essay Topics & Examples

Have some suggestions and questions about nature vs nurture? On this page, find research and essay topics to explore a particular aspect of the discussion.

📑 Aspects to Cover in a Nature vs Nurture Essay

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What affects human development: nature or nurture? Are gender roles and differences come naturally, or does society impose them? What can be argued about the personalities of identical twins? Explore any of the issues with us! Our IvyPnada team has prepared nurture vs nature topics to write about. Check essay examples via the links as well.

At first glance, a nature vs nurture essay seems to be easy. However, a limited view of the subject matter may cost you marks, which is why it is crucial to offer a well-rounded account of the debate. Here are some of the aspects that you might want to include in your essay on nature vs nurture.

• The importance of the topic. The debate on what influences one’s personality, intelligence, and character is among the most prominent ones in psychology and other social sciences. Your task is to reflect this and to attempt to justify why the debate is so important. What could be done if it were resolved one day? How does the dispute affect other subject fields and topics in psychology? How would the resolution help the study of psychology and human behavior to move forward? Would it help to prove certain theories or refute the others, and what would be the effect on professional practice?
• The origins of the debate. While you explore the first aspect, you might stumble upon the history of the nature vs nurture debate. Covering this theme in your essay could also earn you some extra marks. Merely summarizing historical facts is not enough, though, because your tutor is probably aware of them already. Instead, you should focus on why the debate started. Were there any developments in psychology that prompted it?
• Prominent views. It is hard to omit the opinions expressed by famous scholars while writing an essay on this subject. John Locke, John B. Watson, Calvin Hall, and other authors had all shared ideas on the issue. If you need more names, try searching sample essays on nature and nurture online since most of them point out the key names. This might also help you to identify possible nature vs nurture essay titles.
• Results of research studies. Research evidence is among the key nature vs nurture essay topics because there were many attempts to prove one or the other view. Examples of such studies may be cited in your textbook, so it should be the first point of your research. Your school’s library and Google Scholar might also give you more information. If you find any sources online, make sure that they are of academic quality, or you might lose marks.
• Your personal experience and thoughts. Because the controversy is so prominent, nearly all people who study psychology or social studies have an opinion on it. If the instructions don’t prevent you from doing this, you should share your thoughts on the debate between nature and nurture. Support your opinion with credible research evidence and link it to the work of other scholars. If you believe that the environment is more important than genes, why is that? What other theorists supported this view, and why did they? Your opinion, supported by relevant facts and views, may become an excellent nature vs nurture essay thesis.
• Suggestions for further research. Try to think about what could be done to resolve the debate once and for all. What are the main gaps in studies on nature vs nurture and how could they be addressed by scholars?

Covering all of the themes above will help you to produce an outstanding essay. Make sure to check our website for a nature vs nurture essay prompt, titles, and other useful materials!

• Nature vs. Nurture In most cases, nature determines the physical characteristics which in effect influence the behavior of an individual. These are traits which largely determined by the socio-cultural environmental factors or the way the individuals are socialized […]
• Human Development: Nature or Nurture? With studies and theories carried out to examine the impact of nature on the personal development and personality traits, heredity is an important factor in the development.
• As Nature Made Him: Summary and Analysis As aforementioned, the author of this book provides useful analysis of this aspect of personality. One of the greatest questions that readers get answer from this book is the question of nature vs.nurture in sexuality […]
• Nature vs. Nurture: “In Cold Blood” by Truman Capote Thus, by contrasting Dick’s nurturing in love and affection and the conditions of his blissful childhood and adolescence with the details of a horrible crime committed by him and his attitude to it, the author […]
• Physical and Mental Wellbeing: Nature Versus Nurture In conclusion, the debates on nature versus nurture reveal that both innate health conditions and external factors shape the outcomes for physical and mental wellbeing of an individual.
• Nature Versus Nurture and Learning Among Children Of much concern among modern researchers is the determination of the degree of influence of nature and nurture on the development of a child and the provision of learning experiences.
• Violent Behavior: Nature vs. Nurture Considering this circumstance, the shifts in one’s attitudes are likely to be ascribed to the modifications in conditions, which can be reported by families with children.
• “Nature” Versus “Nurture”: Effects on Child Development Consequently, a child’s behavior cannot be viewed as solely attributable to the genetic composition of the parents and the hereditary characteristics.
• Nature vs. Nurture: New Science Stirs Debate How Behavior Is Shaped A prime example of this nature of debates is the debate on whether nature or nurture has a greater bearing on the development of the diverse individual behavioral differences that exist.
• Alcoholism-Nature vs. Nurture Debate The analysis on physiological physiology regarding alcohol shows that, alcohol displays feelings of superiority and fearless behavior and also, it reduces an individual’s fear.
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• The Role of Nature and Nurture: Adolescence Eating Disorders
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• The Impact of Nature and Nurture on Huck’s and Finn’s Personality and Behavior in the Adventure of Huckleberry Finn by Mark Twain
• The Correlation Between Nature and Nurture in the Personal Development
• Role of Nature and Nurture in Language Development
• Personality, Behavior, and the Significance of Nature vs. Nurture
• The Disputes Concerning the Popular Nature vs. Nurture Argument
• Understanding the Role of Nature Versus Nurture in Alcohol Addiction
• Wild Child vs. Nature and Nurture
• The Importance of Nature Verses Nurture in Shaping Behavior and Personality
• The Differences Between Boys and Girls from Combination Between Nature and Nurture
• The Role of Nature and Nurture in Human Homosexuality
• The Nature Versus Nurture Debate in the Blasphemy of Talking Politics During Bach Year, an Article by Susan McClary
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• What Differentiates the Entrepreneurs From Non-Entrepreneurs on Nature and Nurture
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• Gender and Socialization: Nature or Nurture
• How Nature and Nurture Affects the Pies in Adolescence and Adulthood
• The Debate Between Criminal Nature and Criminal Nurture: William Sheldon Theory
• The Nurture and Care From Nature and the Damage Caused by Humans to Our Environment
• The Evolutionary Theory of Nature vs. Nurture
• The Personality and Biology Differences in Nature Versus Nurture and Man Versus Woman Situations in Daily Life
• The Importance of Twin Studies in the Nature Versus Nurture Debate
• The Scientific and Cultural Debate of Nature vs. Nurture
• The Issue of Nature Versus Nurture in the Development of Serial Killers
• The Role of Nature vs. Nurture, Culture and Gender, and Family
• What Makes a Monster Nature vs. Nurture in Mary Shelleys Frankenstein
• The Theme of Nature Versus Nurture in Shelly’s Frankenstein
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• How Children Develop and the Interplay of Nature vs. Nurture?
• How Nature vs. Nurture Affect Human Development?
• Homosexuality: Nature vs. Nurture?
• How Do Nature vs. Nurture Work Together Example?
• How Does Nature vs. Nurture Affect Human Behavior?
• Why Is Nature vs. Nurture Called a False Debate?
• Nature vs. Nurture: Do Our Genes Affect Our Personalities?
• Nature vs. Nurture: Which Has a More Significant Influence on Child Development?
• How Do You Argue Nature vs. Nurture?
• Nature vs. Nurture: Who’s to Blame for Acts of Violence?
• How Does Nature vs. Nurture Affect Intelligence?
• Nature vs. Nurture: Which Is the Origin of Virtue?
• How Does Shelley Represent the Nature vs. Nurture Debate?
• Nature vs. Nurture: Which Determines Personality?
• What Are Examples of Nature vs. Nurture?
• Nature vs. Nurture: What Does Matter More?
• What Is Stronger Nurture vs. Nature?
• Why Nurture Is Better Than Nature?
• How Does the Nature vs. Nurture Debate in May Affect the Physical?
• What Is Nature vs. Nurture in Child Development?
• How Nature vs. Nurture Influence Substance Abuse?
• Twin Studies: What Can They Tell Us About Nature vs. Nurture?
• How Does Nature vs. Nurture Affect the Development of Social-Emotion Attributes?
• Who Won Nature vs. Nurture?
• How Nature vs. Nurture Apply the Principles of Life?
• What Is the Difference Between Nature vs. Nurture in Child Development?
• What Is the Main Idea of Nature vs. Nurture?
• Is Nature vs. Nurture Misleading?
• Nature vs. Nurture: What Impacts a Child’s IQ?
• How Does Nature vs. Nurture Affect Human Development?
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Article contents

Nature and nurture as an enduring tension in the history of psychology.

• Hunter Honeycutt Hunter Honeycutt Bridgewater College, Department of Psychology
• https://doi.org/10.1093/acrefore/9780190236557.013.518
• Published online: 30 September 2019

Nature–nurture is a dichotomous way of thinking about the origins of human (and animal) behavior and development, where “nature” refers to native, inborn, causal factors that function independently of, or prior to, the experiences (“nurture”) of the organism. In psychology during the 19th century, nature-nurture debates were voiced in the language of instinct versus learning. In the first decades of the 20th century, it was widely assumed that that humans and animals entered the world with a fixed set of inborn instincts. But in the 1920s and again in the 1950s, the validity of instinct as a scientific construct was challenged on conceptual and empirical grounds. As a result, most psychologists abandoned using the term instinct but they did not abandon the validity of distinguishing between nature versus nurture. In place of instinct, many psychologists made a semantic shift to using terms like innate knowledge, biological maturation, and/or hereditary/genetic effects on development, all of which extend well into the 21st century. Still, for some psychologists, the earlier critiques of the instinct concept remain just as relevant to these more modern usages.

The tension in nature-nurture debates is commonly eased by claiming that explanations of behavior must involve reference to both nature-based and nurture-based causes. However, for some psychologists there is a growing pressure to see the nature–nurture dichotomy as oversimplifying the development of behavior patterns. The division is seen as both arbitrary and counterproductive. Rather than treat nature and nurture as separable causal factors operating on development, they treat nature-nurture as a distinction between product (nature) versus process (nurture). Thus there has been a longstanding tension about how to define, separate, and balance the effects of nature and nurture.

• nature–nurture
• development
• nativism–empiricism
• innate–learned
• behavioral genetics
• epigenetics

Nature and Nurture in Development

The oldest and most persistent ways to frame explanations about the behavioral and mental development of individuals is to distinguish between two separate sources of developmental causation: (a) intrinsic, preformed, or predetermined causes (“nature”) versus (b) extrinsic, experiential, or environmental causes (“nurture”). Inputs from these two sources are thought to add their own contribution to development (see Figure 1 ).

Figure 1. The traditional view of nature and nurture as separate causes of development. In the traditional view, nature and nurture are treated as independent causal influences that combine during development to generate outcomes. Note that, during development, the effects of nature and nurture (shown in horizontal crossing lines) remain independent so that their effects on outcomes are theoretically separable.

Because some traits seem to derive more from one source than the other, much of the tension associated with the nature–nurture division deals with disagreements about how to balance the roles of nature and nurture in the development of a trait.

Evidence of Nature in Development

Evidence to support the nature–nurture division usually derives from patterns of behavior that suggest a limited role of environmental causation, thus implying some effect of nature by default. Table 1 depicts some common descriptors and conditions used to infer that some preference, knowledge, or skill is nature based.

Table 1. Common Descriptors and Associated Conditions for Inferring the Effects of Nature on Development

It is important to reiterate that nature-based causation (e.g., genetic determination) is inferred from these observations. Such inferences can generate tension because each of the observations listed here can be explained by nurture-based (environmental) factors. Confusion can also arise when evidence of one descriptor (e.g., being hereditary) is erroneously used to justify a different usage (e.g., that the trait is unlearned).

The Origins of Nature Versus Nurture

For much of recorded history, the distinction between nature and nurture was a temporal divide between what a person is innately endowed with at birth, prior to experience (nature), and what happens thereafter (nurture). It was not until the 19th century that the temporal division was transformed into a material division of causal influences (Keller, 2010 ). New views about heredity and Darwinian evolution justified distinguishing between native traits and genetic causes from acquired traits and environmental causes. More so than before, the terms nature and nurture were often juxtaposed in an opposition famously described by Sir Francis Galton ( 1869 ) as that between “nature versus nurture.”

Galton began writing about heredity in the mid-1860s. He believed we would discover laws governing the transmission of mental as well as physical qualities. Galton’s take on mental heredity, however, was forged by his desire to improve the human race in a science he would later call “eugenics.” In the mid- 19th century , British liberals assumed humans were equivalent at birth. Their social reform efforts were geared to enhancing educational opportunities and improving living conditions. Galton, a political conservative, opposed the notion of natural equality, arguing instead that people were inherently different at birth (Cowan, 2016 ), and that these inherited mental and behavioral inequalities were transmitted through lineages like physical qualities. Because Galton opposed the widely held Lamarckian idea that the qualities acquired in one’s lifetime could modify the inherited potential of subsequent generations, he believed long-lasting improvement of the human stock would only come by controlling breeding practices.

To explain the biological mechanisms of inheritance, Galton joined a growing trend in the 1870s to understand inheritance as involving the transmission of (hypothetical) determinative, germinal substances across generations. Foreshadowing a view that would later become scientific orthodoxy, Galton believed these germinal substances to be uninfluenced by the experiences of the organism. His theory of inheritance, however, was speculative. Realizing he was not equipped to fully explicate his theory of biological inheritance, Galton abandoned this line of inquiry by the end of that decade and refocused his efforts on identifying statistical laws of heredity of individual differences (Renwick, 2011 ).

Historians generally agree that Galton was the first to treat nature (as heredity) and nurture (everything else) as separate causal forces (Keller, 2010 ), but the schism gained biological legitimacy through the work of the German cytologist Auguste Weismann in the 1880s. Whereas Galton’s theory was motivated by his political agenda, Weismann was motivated by a scientific, theoretical agenda. Namely, Weismann opposed Lamarckian inheritance and promoted a view of evolution driven almost entirely by natural selection.

Drawing upon contemporary cytological and embryological research, Weismann made the case that the determinative substances found in the germ cells of plants and animals (called the “germ-plasm”) that are transmitted across generations were physically sequestered very early in embryogenesis and remained buffered from the other cells of the body (“somato-plasm”). This so-called, Weismann’s barrier meant that alterations in the soma that develop in the lifetime of the organism through the use or disuse of body parts would not affect the germinal substances transmitted during reproduction (see Winther, 2001 , for review). On this view, Lamarckian-style inheritance of acquired characteristics was not biologically possible.

Galton and Weismann’s influence on the life sciences cannot be overstated. Their work convinced many to draw unusually sharp distinctions between the inherited (nature) and the acquired (nurture). Although their theories were met with much resistance and generated significant tension in the life sciences from cytology to psychology, their efforts helped stage a new epistemic space through which to appreciate Mendel’s soon to be rediscovered breeding studies and usher in genetics (Muller-Wille & Rheinberger, 2012 ).

Ever since, psychology has teetered between nature-biased and nurture-biased positions. With the rise of genetics, the wedge between nature–nurture was deepened in the early to mid- 20th century , creating fields of study that focused exclusively on the effects of either nature or nurture.

The “Middle Ground” Perspective on Nature–Nurture

Twenty-first-century psychology textbooks often state that the nature–nurture debates have been resolved, and the tension relaxed, because we have moved on from emphasizing nature or nurture to appreciating that development necessarily involves both nature and nurture. In this middle-ground position, one asks how nature and nurture interact. For example, how do biological (or genetic) predispositions for behaviors or innate knowledge bias early learning experiences? Or how might environmental factors influence the biologically determined (maturational) unfolding of bodily form and behaviors?

Rejection of the Nature–Nurture Divide

For some, the “middle-ground” resolution is as problematic as “either/or” views and does not resolve a deeper source of tension inherent in the dichotomy. On this view, the nature–nurture divide is neither a legitimate nor a constructive way of thinking about development. Instead, developmental analysis reveals that the terms commonly associated with nature (e.g., innate, genetic, hereditary, or instinctual) and nurture (environmental or learned) are so entwined and confounded (and often arbitrary) that their independent effects cannot be meaningfully discussed. The nature–nurture division oversimplifies developmental processes, takes too much for granted, and ultimately hinders scientific progress. Thus not only is there a lingering tension about how to balance the effects of nature and nurture in the middle-ground view, but there is also a growing tension to move beyond the dichotomous nature–nurture framework.

Nativism in Behavior: Instincts

Definitions of instinct can vary tremendously, but many contrast (a) instinct with reason (or intellect, thought, will), which is related to but separable from contrasting (b) instinct with learning (or experience or habit).

Instinct in the Age of Enlightenment

Early usages of the instinct concept, following Aristotle, treated instinct as a mental, estimative faculty ( vis aestimativa or aestimativa naturalis ) in humans and animals that allowed for the judgments of objects in the world (e.g., seeing a predator) to be deemed beneficial or harmful in a way that transcends immediate sensory experience but does not involve the use of reason (Diamond, 1971 ). In many of the early usages, the “natural instinct” of animals even included subrational forms of learning.

The modern usage of instincts as unlearned behaviors took shape in the 17th century . By that point it was widely believed that nature or God had implanted in animals and humans innate behaviors and predispositions (“instincts”) to promote the survival of the individual and the propagation of the species. Disagreements arose as to whether instincts derived from innate mental images or were mindlessly and mechanically (physiologically) generated from innately specified bodily organization (Richards, 1987 ).

Anti-Instinct Movement in the Age of Enlightenment

Challenges to the instinct concept can be found in the 16th century (see Diamond, 1971 ), but they were most fully developed by empiricist philosophers of the French Sensationalist tradition in the 18th century (Richards, 1987 ). Sensationalists asserted that animals behaved rationally and all of the so-called instincts displayed by animals could be seen as intelligently acquired habits.

For Sensationalists, instincts, as traditionally understood, did not exist. Species-specificity in behavior patterns could be explained by commonalities in physiological organization, needs, and environmental conditions. Even those instinctual behaviors seen at birth (e.g., that newly hatched chicks peck and eat grain) might eventually be explained by the animal’s prenatal experiences. Erasmus Darwin ( 1731–1802 ), for example, speculated that the movements and swallowing experiences in ovo could account for the pecking and eating of grain by young chicks. The anti-instinct sentiment was clearly expressed by the Sensationalist Jean Antoine Guer ( 1713–1764 ), who warned that instinct was an “infantile idea” that could only be held by those who are ignorant of philosophy, that traditional appeals to instincts in animals not only explained nothing but served to hinder scientific explanations, and that nothing could be more superficial than to explain behavior than appealing to so-called instincts (Richards, 1987 ).

The traditional instinct concept survived. For most people, the complex, adaptive, species-specific behaviors displayed by naïve animals (e.g., caterpillars building cocoons; infant suckling behaviors) appeared to be predetermined and unlearned. Arguably as important, however, was the resistance to the theological implications of Sensationalist philosophy.

One of the strongest reactions to Sensationalism was put forward in Germany by Herman Samuel Reimarus ( 1694–1768 ). As a natural theologian, Reimarus, sought evidence of a God in the natural world, and the species-specific, complex, and adaptive instincts of animals seemed to stand as the best evidence of God’s work. More so than any other, Reimarus extensively catalogued instincts in humans and animals. Rather than treat instincts as behaviors, he defined instincts as natural impulses (inner drives) to act that were expressed perfectly, without reflection or practice, and served adaptive goals (Richards, 1987 ). He even proposed instincts for learning, a proposal that would resurface in the mid- 20th century , as would his drive theory of instinct (Jaynes & Woodward, 1974 ).

Partly as a result of Reimarus’ efforts, the instinct concept survived going into the 19th century . But many issues surrounding the instinct concept were left unsettled. How do instincts differ from reflexive behaviors? What role does learning play in the expression of instincts, if any? Do humans have more or fewer instincts than animals? These questions would persist well into the first decades of the 20th century and ultimately fuel another anti-instinct movement.

Instinct in the 19th Century

In the 19th century , the tension about the nature and nurture of instincts in the lifetime of animals led to debates about the nature and nurture of instincts across generations . These debates dealt with whether instincts should be viewed as “inherited habits” from previous generations or whether they result from the natural selection. Debating the relative roles of neo-Lamarckian use-inheritance versus neo-Darwinian natural selection in the transmutation of species became a significant source of tension in the latter half of the 19th century . Although the neo-Lamarckian notion of instincts as being inherited habits was rejected in the 20th century , it has resurged in recent years (e.g., see Robinson & Barron, 2017 ).

Darwinian evolutionary theory required drawing distinctions between native and acquired behaviors, and, perhaps more so than before, behaviors were categorized along a continuum from the purely instinctive (unlearned), to the partially instinctive (requiring some learning), to the purely learned. Still, it was widely assumed that a purely instinctive response would be modified by experience after its first occurrence. As a result, instinct and habit were very much entangled in the lifetime of the organism. The notion of instincts as fixed and unmodifiable would not be widely advanced until after the rise of Weismann’s germ-plasm theory in the late 19thcentury .

Given their importance in evolutionary theory, there was greater interest in more objectively identifying pure instincts beyond anecdotal reports. Some of the most compelling evidence was reported by Douglas Spalding ( 1844–1877 ) in the early 1870s (see Gray, 1967 ). Spalding documented numerous instances of how naïve animals showed coordinated, seemingly adaptive responses (e.g., hiding) to objects (e.g., sight of predators) upon their first encounter, and he helped pioneer the use of the deprivation experiment to identify instinctive behaviors. This technique involved selectively depriving young animals of seemingly critical learning experiences or sensory stimulation. Should animals display some species-typical action following deprivation, then, presumably, the behavior could be labeled as unlearned or innate. In all, these studies seemed to show that animals displayed numerous adaptive responses at the very start, prior to any relevant experience. In a variety of ways, Spalding’s work anticipated 20th-century studies of innate behavior. Not only would the deprivation experiment be used as the primary means of detecting native tendencies by European zoologists and ethologists, but Spalding also showed evidence of what would later be called imprinting, critical period effects and evidence of behavioral maturation.

Reports of pure instinct did not go unchallenged. Lloyd Morgan ( 1896 ) questioned the accuracy of these reports in his own experimental work with young animals. In some cases, he failed to replicate the results and in other cases he found that instinctive behaviors were not as finely tuned to objects in the environment as had been claimed. Morgan’s research pointed to taking greater precision in identifying learned and instinctive components of behavior, but, like most at the turn of the 20th century , he did not question that animal behavior involved both learned and instinctive elements.

A focus on instinctive behaviors intensified in the 1890s as Weismann’s germ-plasm theory grew in popularity. More so than before, a sharp distinction was drawn between native and acquired characteristics, including behavior (Johnston, 1995 ). Although some psychologists continued to maintain neo-Lamarckian notions, most German (Burnham, 1972 ) and American (Cravens & Burnham, 1971 ) psychologists were quick to adopt Weismann’s theory. They envisioned a new natural science of psychology that would experimentally identify the germinally determined, invariable set of native psychological traits in species and their underlying physiological (neural) basis. However, whereas English-speaking psychologists tended to focus on how this view impacted our understanding of social institutions and its social implications, German psychologists were more interested in the longstanding philosophical implications of Weismann’s doctrine as it related to the differences (if any) between man and beast (Burnham, 1972 ).

Some anthropologists and sociologists, however, interpreted Weismann’s theory quite differently and used it elevate sociology as its own scientific discipline. In the 1890s, the French sociologist Emil Durkheim, for example, interpreted Weismann’s germinal determinants as a generic force on human behavior that influenced the development of general predispositions that are molded by the circumstances of life (Meloni, 2016 ). American anthropologists reached similar conclusions in the early 20th century (Cravens & Burnham, 1971 ). Because Weismann’s theory divorced biological inheritance from social inheritance, and because heredity was treated as a generic force, sociologists felt free to study social (eventually, “cultural”) phenomena without reference to biological or psychological concerns.

Anti-Instinct Movement in the 1920s

Despite their differences, in the first two decades of the 20th century both psychologists and sociologists generally assumed that humans and animals had some native tendencies or instincts. Concerns were even voiced that instinct had not received enough attention in psychology. Disagreements about instincts continued to focus on (the now centuries old debates of) how to conceptualize them. Were they complex reflexes, impulses, or motives to act, or should instinct be a mental faculty (like intuition), separate from reasoning and reflex (Herrnstein, 1972 )?

In America, the instinct concept came under fire following a brief paper in 1919 by Knight Dunlap titled “Are There Any Instincts?” His primary concern dealt with teleological definitions of instincts in which an instinct referred to all the activities involved in obtaining some end-state (e.g., instincts of crying, playing, feeding, reproduction, war, curiosity, or pugnacity). Defined in this way, human instincts were simply labels for human activities, but how these activities were defined was arbitrarily imposed by the researchers. Is feeding, for instance, an instinct, or is it composed of more basic instincts (like chewing and swallowing)? The arbitrariness of classifying human behavior had led to tremendous inconsistencies and confusion among psychologists.

Not all of the challenges to instinct dealt with its teleological usage. Some of the strongest criticisms were voiced by Zing-Yang Kuo throughout the 1920s. Kuo was a Chinese animal psychologist who studied under Charles Tolman at the University of California, Berkeley. Although Kuo’s attacks on instinct changed throughout the 1920s (see Honeycutt, 2011 ), he ultimately argued that all behaviors develop in experience-dependent ways and that appeals to instinct were statements of ignorance about how behaviors develop. Like Dunlap, he warned that instincts were labels with no explanatory value. To illustrate, after returning to China, he showed how the so-called rodent-killing instinct in cats often cited by instinct theorists is not found in kittens that are reared with rodents (Kuo, 1930 ). These kittens, instead, became attached to the rodents, and they resisted attempts to train rodent-killing. Echoing the point made by Guer, Kuo claimed that appeals to instinct served to stunt scientific inquiry into the developmental origins of behavior.

But Kuo did not just challenge the instinct concept. He also argued against labeling behaviors as “learned.” After all, whether an animal “learns” depends on the surrounding environmental conditions, the physiological and developmental status of the animal, and, especially, the developmental (or experiential) history of that animal. Understanding learning also required developmental analysis. Thus Kuo targeted the basic distinction between nature and nurture, and he was not alone in doing so (e.g., see Carmichael, 1925 ), but his call to reject it did not spread to mainstream American psychologists.

By the 1930s, the term instinct had fallen into disrepute in psychology, but experimental psychologists (including behaviorists) remained committed to a separation of native from acquired traits. If anything, the dividing line between native and acquired behaviors became more sharply drawn than before (Logan & Johnston, 2007 ). For some psychologists, instinct was simply rebranded in the less contentious (but still problematic) language of biological drives or motives (Herrnstein, 1972 ). Many other psychologists simply turned to describing native traits as due to “maturation” and/or “heredity” rather than “instinct.”

Fixed Action Patterns

The hereditarian instinct concept received a reboot in Europe in the 1930s with the rise of ethology led by Konrad Lorenz, Niko Tinbergen, and others. Just as animals inherit organs that perform specific functions, ethologists believed animals inherit behaviors that evolved to serve adaptive functions as well. Instincts were described as unlearned (inherited), blind, stereotyped, adaptive, fixed action patterns, impervious to change that are initiated (released) by specific stimuli in the environment.

Ethologists in 1930s and 1940s were united under the banner of innateness. They were increasingly critical of the trend by American psychologists (i.e., behaviorists) to focus on studying on how a limited number of domesticated species (e.g., white rat) responded to training in artificial settings (Burkhardt, 2005 ). Ethologists instead began with rich descriptions of animal behavior in more natural environments along with detailed analyses of the stimulus conditions that released the fixed action patterns. To test whether behavioral components were innate, ethologists relied primarily on the deprivation experiment popularized by Spalding in the 19th century . Using these methods (and others), ethologists identified numerous fascinating examples of instinctive behaviors, which captured mainstream attention.

In the early 1950s, shortly after ethology had gained professional status (Burkhardt, 2005 ), a series of challenges regarding instinct and innateness were put forth by a small cadre of North American behavioral scientists (e.g., T. C. Schneirla, Donald Hebb, Frank Beach). Arguably the most influential critique was voiced by comparative psychologist Daniel Lehrman ( 1953 ), who presented a detailed and damning critique of deprivation experiments on empirical and logical grounds. Lehrman explained that deprivation experiments isolate the animal from some but not all experiences. Thus deprivation experiments simply change what an animal experiences rather than eliminating experience altogether, and so they cannot possibly determine whether a behavior is innate (independent of experience). Instead, these experiments show what environmental conditions do not matter in the development of a behavior but do not speak to what conditions do matter .

Lehrman went on to argue that the whole endeavor to identify instinctive or innate behavior was misguided from the start. All behavior, according to Lehrman, develops from a history of interactions between an organism and its environment. If a behavior is found to develop in the absence of certain experiences, the researcher should not stop and label it as innate. Rather, research should continue to identify the conditions under which the behavior comes about. In line with Kuo, Lehrman repeated the warning that to label something as instinctive (or inherited or maturational) is a statement of ignorance about how that behavior develops and does more to stunt than promote research.

Lehrman’s critique created significant turmoil among ethologists. As a result, ethologists took greater care in using the term innate , and it led to new attempts to synthesize or re-envision learning and instinct .

Some of these attempts focused on an increased role for learning and experience in the ontogeny of species-typical behaviors. These efforts spawned significant cross-talk between ethologists and comparative psychologists to more thoroughly investigate behavioral development under natural conditions. Traditional appeals to instinct and learning (as classical and operant conditioning) were both found to be inadequate for explaining animal behavior. In their stead, these researchers focused more closely on how anatomical, physiological, experiential, and environmental conditions influenced the development of species-typical behaviors.

Tinbergen ( 1963 ) was among those ethologists who urged for greater developmental analysis of species-typical behaviors, and he included it as one of his four problems in the biological study of organisms, along with causation (mechanism), survival value (function), and evolution. Of these four problems, Tinbergen believed ethologists were especially well suited to study survival value, which he felt had been seriously neglected (Burkhardt, 2005 ).

The questions of survival value coupled with models of population genetics would gain significant momentum in the 1960s and 1970s in England and the United States with the rise of behavioral ecology and sociobiology (Griffiths, 2008 ). But because these new fields seemed to promote some kind of genetic determinism in behavioral development, they were met with much resistance and reignited a new round of nature–nurture debates in the 1970s (see Segerstrale, 2000 ).

However, not all ethologists abandoned the instinct concept. Lorenz, in particular, continued to defend the division between nature and nurture. Rather than speaking of native and acquired behaviors, Lorenz later spoke of two different sources of information for behavior (innate/genetic vs. acquired/environmental), which was more a subtle shift in language than it was an actual change in theory, as Lehrman later pointed out.

Some ethologists followed Lorenz’s lead and continued to maintain more of a traditional delineation between instinct and learning. Their alternative synthesis viewed learning as instinctive (Gould & Marler, 1987 ). They proposed that animals have evolved domain-specific “instincts to learn” that result from the its genetic predispositions and innate knowledge. To support the idea of instincts for learning, ethologists pointed to traditional ethological findings (on imprinting and birdsong learning), but they also drew from the growing body of work in experimental psychology that seemed to indicate certain types of biological effects on learning.

Biological Constraints and Preparedness

While ethology was spreading in Europe in the 1930s–1950s, behaviorism reigned in the United States. Just as ethologists were confronted with including a greater role of nurture in their studies, behaviorists were challenged to consider a greater role of nature.

Behaviorists assumed there to be some behavioral innateness (e.g., fixed action patterns, unconditioned reflexes, primary reinforcers and drives). But because behaviorists focused on learning, they tended to study animals in laboratory settings using biologically (or ecologically) irrelevant stimuli and responses to minimize any role of instinct (Johnston, 1981 ). It was widely assumed that these studies would identify general laws of learning that applied to all species regardless of the specific cues, reinforcers, and responses involved.

Challenges to the generality assumption began to accumulate in the 1960s. Some studies pointed to failures that occurred during conditioning procedures. Breland and Breland ( 1961 ), for example, reported that some complex behaviors formed through operant conditioning would eventually become “displaced” by conditioned fixed action patterns in a phenomenon they called “instinctive drift.” Studies of taste-aversion learning (e.g., Garcia & Koelling, 1966 ) also reported the failure of rats to associate certain events (e.g., flavors with shock or audiovisual stimuli with toxicosis).

Other studies were pointing to enhanced learning. In particular, it was found that rats could form strong conditioned taste aversions after only a single pairing between a novel flavor and illness. (This rapid “one trial learning” was a major focus in the research from Niko Tinbergen’s ethological laboratory.) Animals, it seemed, had evolved innate predispositions to form (or not form) certain associations.

In humans, studies of biological constraints on learning were mostly limited to fear conditioning. Evidence indicated that humans conditioned differently to (biologically or evolutionarily) fear-relevant stimuli like pictures of spiders or snakes than to fear-irrelevant stimuli like pictures of mushrooms or flowers (Ohman, Fredrikson, Hugdahl, & Rimmö, 1976 ).

These findings and others were treated as a major problem in learning theory and led to calls for a new framework to study learning from a more biologically oriented perspective that integrated the evolutionary history and innate predispositions of the species. These predispositions were described as biological “constraints” on, “preparedness,” or “adaptive specializations” for learning, all of which were consistent with the “instincts to learn” framework proposed by ethologists.

By the 1980s it was becoming clear that the biological preparedness/constraint view of learning suffered some limitations. For example, what constraints count as “biological” was questioned. It was well established that there were general constraints on learning associated with the intensity, novelty, and timing of stimuli. But, arbitrarily it seemed, these constraints were not classified as “biological” (Domjan & Galef, 1983 ). Other studies of “biological constraints” found that 5- and 10-day old rats readily learned to associated a flavor with shock (unlike in adults), but (like in adults) such conditioning was not found in 15-day-old rats (Hoffman & Spear, 1988 ). In other words, the constraint on learning was not present in young rats but developed later in life, suggesting a possible role of experience in bringing about the adult-like pattern.

Attempts to synthesize these alternatives led to numerous calls for more ecologically oriented approaches to learning not unlike the synthesis between ethology and comparative psychology in the 1960s. All ecological approaches to learning proposed that learning should be studied in the context of “natural” (recurrent and species-typical) problems that animals encounter (and have evolved to encounter) using ecologically meaningful stimuli and responses. Some argued (e.g., Johnston, 1981 ) that studies of learning should take place within the larger context of studying how animals develop and adapt to their surround. Others (Domjan & Galef, 1983 ) pointed to more of a comparative approach in studying animal learning in line with behavioral ecology that takes into account how learning can be influenced by the possible selective pressures faced by each species. Still, how to synthesize biological constraints (and evolutionary explanations) on learning with a general process approach remains a source of tension in experimental psychology.

Nativism in Mind: Innate Ideas

Nativism and empiricism in philosophy.

In the philosophy of mind, nature–nurture debates are voiced as debates between nativists and empiricists. Nativism is a philosophical position that holds that our minds have some innate (a priori to experience) knowledge, concepts, or structure at the very start of life. Empiricism, in contrast, holds that all knowledge derives from our experiences in the world.

However, rarely (if ever) were there pure nativist or empiricist positions, but the positions bespeak a persistent tension. Empiricists tended to eschew innateness and promote a view of the mental content that is built by general mechanisms (e.g., association) operating on sensory experiences, whereas nativists tend to promote a view of mind that contains domain-specific, innate processes and/or content (Simpson, Carruthers, Laurence, & Stich, 2005 ). Although the tension about mental innateness would loosen as empiricism gained prominence in philosophy and science, the strain never went away and would intensify again in the 20th century .

Nativism in 20th Century Psychology: The Case of Language Development

In the first half of the 20th century , psychologists generally assumed that knowledge was gained or constructed through experience with the world. This is not to say that psychologists did not assume some innate knowledge. The Swiss psychologist Jean Piaget, for example, believed infants enter the world with some innate knowledge structures, particularly as they relate to early sensory and motor functioning (see Piaget, 1971 ). But the bulk of his work dealt with the construction of conceptual knowledge as children adapt to their worlds. By and large, there were no research programs in psychology that sought to identify innate factors in human knowledge and cognition until the 1950s (Samet & Zaitchick, 2017 )

An interest in psychological nativism was instigated in large part by Noam Chomsky’s ( 1959 ) critique of B. F. Skinner’s book on language. To explain the complexity of language, he argued, we must view language as the knowledge and application of grammatical rules. He went on to claim that the acquisition of these rules could not be attributed to any general-purpose, learning process (e.g., reinforcement). Indeed, language acquisition occurs despite very little explicit instruction. Moreover, language is special in terms of its complexity, ease, and speed of acquisition by children and in its uniqueness to humans. Instead, he claimed that our minds innately contain some language-specific knowledge that kick-starts and promotes language acquisition. He later claimed this knowledge can be considered some sort of specialized mental faculty or module he called the “language acquisition device” (Chomsky, 1965 ) or what Pinker ( 1995 ) later called the “language instinct.”

To support the idea of linguistic nativism, Chomsky and others appealed to the poverty of the stimulus argument. In short, this argument holds that our experiences in life are insufficient to explain our knowledge and abilities. When applied to language acquisition, this argument holds children’s knowledge of language (grammar) goes far beyond the limited, and sometimes broken, linguistic events that children directly encounter. Additional evidence for nativism drew upon the apparent maturational quality of language development. Despite wide variations in languages and child-rearing practices across the world, the major milestones in language development appear to unfold in children in a universal sequence and timeline, and some evidence suggested a critical period for language acquisition.

Nativist claims about language sparked intense rebuttals by empiricist-minded psychologists and philosophers. Some of these retorts tackled the logical limitations of the poverty of stimulus argument. Others pointed to the importance of learning and social interaction in driving language development, and still others showed that language (grammatical knowledge) may not be uniquely human (see Tomasello, 1995 , for review). Nativists, in due course, provided their own rebuttals to these challenges, creating a persistent tension in psychology.

Extending Nativism Beyond Language Development

In the decades that followed, nativist arguments expanded beyond language to include cognitive domains that dealt with understanding the physical, psychological, and social worlds. Developmental psychologists were finding that infants appeared to be much more knowledgeable in cognitive tasks (e.g., on understanding object permanence) and skillful (e.g., in imitating others) than had previously been thought, and at much younger ages. Infants also showed a variety of perceptual biases (e.g., preference for face-like stimuli over equally complex non-face-like stimuli) from very early on. Following the standard poverty of the stimulus argument, these findings were taken as evidence that infants enter the world with some sort of primitive, innate, representational knowledge (or domain-specific neural mechanisms) that constrains and promotes subsequent cognitive development. The nature of this knowledge (e.g., as theories or as core knowledge), however, continues to be debated (Spelke & Kinzler, 2007 ).

Empiricist-minded developmental psychologists responded by demonstrating shortcomings in the research used to support nativist claims. For example, in studies of infants’ object knowledge, the behavior of infants (looking time) in nativist studies could be attributed to relatively simple perceptual processes rather than to the infants’ conceptual knowledge (Heyes, 2014 ). Likewise, reports of human neonatal imitation not only suffered from failures to replicate but could be explained by simpler mechanisms (e.g., arousal) than true imitation (Jones, 2017 ). Finally, studies of perceptual preferences found in young infants, like newborn preferences for face-like stimuli, may not be specific preferences for faces per se but instead may reflect simpler, nonspecific perceptual biases (e.g., preferences for top-heavy visual configurations and congruency; Simion & Di Giorgio, 2015 ).

Other arguments from empiricist-minded developmental psychologists focused on the larger rationale for inferring innateness. Even if it is conceded that young infants, like two-month-olds, or even two-day-olds, display signs of conceptual knowledge, there is no good evidence to presume the knowledge is innate. Their knowledgeable behaviors could still be seen as resulting from their experiences (many of which may be nonobvious to researchers) leading up to the age of testing (Spencer et al., 2009 ).

In the 21st century , there is still no consensus about the reality, extensiveness, or quality of mental innateness. If there is innate knowledge, can experience add new knowledge or only expand the initial knowledge? Can the doctrine of innate knowledge be falsified? There are no agreed-upon answers to these questions. The recurring arguments for and against mental nativism continue to confound developmental psychologists.

Maturation Theory

The emergence of bodily changes and basic behavioral skills sometimes occurs in an invariant, predictable, and orderly sequence in a species despite wide variations in rearing conditions. These observations are often attributed to the operation of an inferred, internally driven, maturational process. Indeed, 21st-century textbooks in psychology commonly associate “nature” with “maturation,” where maturation is defined as the predetermined unfolding of the individual from a biological or genetic blueprint. Environmental factors play a necessary, but fundamentally supportive, role in the unfolding of form.

Preformationism Versus Epigenesis in the Generation of Form

The embryological generation of bodily form was debated in antiquity but received renewed interest in the 17th century . Following Aristotle, some claimed that embryological development involved “epigenesis,” defined as the successive emergence of form from a formless state. Epigenesists, however, struggled to explain what orchestrated development without appealing to Aristotelean souls. Attempts were made to invoke to natural causes like physical and chemical forces, but, despite their best efforts, the epigenesists were forced to appeal to the power of presumed, quasi-mystical, vitalistic forces (entelechies) that directed development.

The primary alternative to epigenesis was “preformationism,” which held that development involved the growth of pre-existing form from a tiny miniature (homunculus) that formed immediately after conception or was preformed in the egg or sperm. Although it seems reasonable to guess that the invention and widespread use of the microscope would immediately lay to rest any claim of homuncular preformationism, this was not the case. To the contrary, some early microscopists claimed to see signs of miniature organisms in sperm or eggs, and failures to find these miniatures were explained away (e.g., the homunculus was transparent or deflated to the point of being unrecognizable). But as microscopes improved and more detailed observations of embryological development were reported in the late 18th and 19th centuries , homuncular preformationism was finally refuted.

From Preformationism to Predeterminism

Despite the rejection of homuncular preformationism, preformationist appeals can be found throughout the 19th century . One of the most popular preformationist theories of embryological development was put forth by Ernst Haeckel in the 1860s (Gottlieb, 1992 ). He promoted a recapitulation theory (not original to Haeckel) that maintained that the development of the individual embryo passes through all the ancestral forms of its species. Ontogeny was thought to be a rapid, condensed replay of phylogeny. Indeed, for Haeckel, phylogenesis was the mechanical cause of ontogenesis. The phylogenetic evolution of the species created the maturational unfolding of embryonic form. Exactly how this unfolding takes place was less important than its phylogenetic basis.

Most embryologists were not impressed with recapitulation theory. After all, the great embryologist Karl Ernst von Baer ( 1792–1876 ) had refuted strict recapitulation decades earlier. Instead, there was greater interest in how best to explain the mechanical causes of development ushering in a new “experimental embryology.” Many experimental embryologists followed the earlier epigenesists by discussing vitalistic forces operating on the unorganized zygote. But it soon became clear that the zygote was structured, and many people believed the zygote contained special (unknown) substances that specified development. Epigenesis-minded experimental embryologists soon warned that the old homuncular preformationism was being transformed into a new predetermined preformationism.

As a result, the debates between preformationism and epigenesis were reignited in experimental embryology, but the focus of these debates shifted to the various roles of nature and nurture during development. More specifically, research focused on the extent to which early cellular differentiation was predetermined by factors internal to cells like chromosomes or cytoplasm (preformationism, nature) or involved factors (e.g., location) outside of the cell (epigenesis, nurture). The former emphasized reductionism and developmental programming, whereas the latter emphasized some sort of holistic, regulatory system responsive to internal and external conditions. The tension between viewing development as predetermined or “epigenetic” persists into the 21st century .

Preformationism gained momentum in the 20th century following the rediscovery of Mendel’s studies of heredity and the rapid rise of genetics, but not because of embryological research on the causes of early differentiation. Instead, preformationism prevailed because it seemed embryological research on the mechanisms of development could be ignored in studies of hereditary patterns.

The initial split between heredity and development can be found in Galton’s speculations but is usually attributed to Weismann’s germ-plasm theory. Weismann’s barrier seemed to posit that the germinal determinants present at conception would be the same, unaltered determinants transmitted during reproduction. This position, later dubbed as “Weismannism,” was ironically not one promoted by Weismann. Like nearly all theorists in the 19th century , he viewed the origins of variation and heredity as developmental phenomena (Amundson, 2005 ), and he claimed that the germ-plasm could be directly modified in the lifetime of the organism by environmental (e.g., climactic and dietary) conditions (Winther, 2001 ). Still, Weismann’s theory treated development as a largely predetermined affair driven by inherited, germinal determinants buffered from most developmental events. As such, it helped set the stage for a more formal divorce between heredity and development with the rise of Mendelism in the early 20th century .

Mendel’s theory of heredity was exceptional in how it split development from heredity (Amundson, 2005 ). More so than in Weismann’s theory, Mendel’s theory assumed that the internal factors that determine form and are transmitted across generations remain unaltered in the lifetime of the organism. To predict offspring outcomes, one need only know the combination of internal factors present at conception and their dominance relations. Exactly how these internal factors determined form could be disregarded. The laws of hereditary transmission of the internal factors (e.g., segregation) did not depend on the development or experiences of the organism or the experiences the organism’s ancestors. Thus the experimental study of heredity (i.e., breeding) could proceed without reference to ancestral records or embryological concerns (Amundson, 2000 ). By the mid-1920s, the Mendelian factors (now commonly called “genes”) were found to be structurally arranged on chromosomes, and the empirical study of heredity (transmission genetics) was officially divorced from studies of development.

The splitting of heredity and development found in Mendel’s and Weismann’s work met with much resistance. Neo-Lamarckian scientists, especially in the United States (Cook, 1999 ) and France (Loison, 2011 ), sought unsuccessfully to experimentally demonstrate the inheritance of acquired characteristics into the 1930s.

In Germany during the 1920s and 1930s, resistance to Mendelism dealt with the chromosomal view of Mendelian heredity championed by American geneticists who were narrowly focused on studying transmission genetics at the expense of developmental genetics. German biologists, in contrast, were much more interested in the broader roles of genes in development (and evolution). In trying to understand how genes influence development, particularly of traits of interest to embryologists, they found the Mendelian theory to be lacking. In the decades between the world wars, German biologists proposed various expanded views of heredity that included some form of cytoplasmic inheritance (Harwood, 1985 ).

Embryologists resisted the preformationist view of development throughout the early to mid- 20th century , often maintaining no divide between heredity and development, but their objections were overshadowed by genetics and its eventual synthesis with evolutionary theory. Consequently, embryological development was treated by geneticists and evolutionary biologists as a predetermined, maturational process driven by internal, “genetic” factors buffered from environmental influence.

Maturation Theory in Psychology

Maturation theory was applied to behavioral development in the 19th century in the application of Haeckel’s recapitulation theory. Some psychologists believed that the mental growth of children recapitulated the history of the human race (from savage brute to civilized human). With this in mind, many people began to more carefully document child development. Recapitulationist notions were found in the ideas of many notable psychologists in the 19th and early 20th centuries (e.g., G. S. Hall), and, as such, the concept played an important role in the origins of developmental psychology (Koops, 2015 ). But for present purposes what is most important is that children’s mental and behavioral development was thought to unfold via a predetermined, maturational process.

With the growth of genetics, maturational explanations were increasingly invoked to explain nearly all native and hereditary traits. As the instinct concept lost value in the 1920s, maturation theory gained currency, although the shift was largely a matter of semantics. For many psychologists, the language simply shifted from “instinct versus learning” to “maturation versus practice/experience” (Witty & Lehman, 1933 ).

Initial lines of evidence for maturational explanations of behavior were often the same as those that justified instinct and native traits, but new embryological research presented in the mid-1920s converged to show support for strict maturational explanations of behavioral development. In these experiments (see Wyman, 2005 , for review), spanning multiple laboratories, amphibians (salamanders and frogs) were exposed to drugs that acted as anesthetics and/or paralytics throughout the early stages of development, thus reducing sensory experience and/or motor practice. Despite the reduced sensory experiences and being unable to move, these animals showed no delays in the onset of motor development once the drugs wore off.

This maturational account of motor development in amphibians fit well with contemporaneous studies of motor development in humans. The orderly, invariant, and predictable (age-related) sequential appearance of motor skills documented in infants reared under different circumstances (in different countries and across different decades) was seen as strong evidence for a maturational account. Additional evidence was reported by Arnold Gessell and Myrtle McGraw, who independently presented evidence in the 1920s to show that the pace and sequence of motor development in infancy were not altered by special training experiences. Although the theories of these maturation theorists were more sophisticated when applied to cognitive development, their work promoted a view in which development was primarily driven by neural maturation rather than experience (Thelen, 2000 ).

Critical and Sensitive Periods

As the maturation account of behavioral development gained ground, it became clear that environmental input played a more informative role than had previously been thought. Environmental factors were found to either disrupt or induce maturational changes at specific times during development. Embryological research suggested that there were well-delineated time periods of heightened sensitivity in which specific experimental manipulations (e.g., tissue transplantations) could induce irreversible developmental changes, but the same manipulation would have no effect outside of that critical period.

In the 1950s–1960s a flurry of critical period effects were reported in birds and mammals across a range of behaviors including imprinting, attachment, socialization, sensory development, bird song learning, and language development (Michel & Tyler, 2005 ). Even though these findings highlighted an important role of experience in behavioral development, evidence of critical periods was usually taken to imply some rigid form of biological determinism (Oyama, 1979 ).

As additional studies were conducted on critical period effects, it became clear that many of the reported effects were more gradual, variable, experience-dependent, and not necessarily as reversible as was previously assumed. In light of these reports, there was a push in the 1970s (e.g., Connolly, 1972 ) to substitute “sensitive period” for “critical period” to avoid the predeterminist connotations associated with the latter and to better appreciate that these periods simply describe (not explain) certain temporal aspects of behavioral development. As a result, a consensus emerged that behaviors should not be attributed to “time” or “age” but to the developmental history and status of the animal under investigation (Michel & Tyler, 2005 ).

Heredity and Genetics

In the decades leading up to and following the start of the 20th century , it was widely assumed that many psychological traits (not just instincts) were inherited or “due to heredity,” although the underlying mechanisms were unknown. Differences in intelligence, personality, and criminality within and between races and sexes were largely assumed to be hereditary and unalterable by environmental intervention (Gould, 1996 ). The evidence to support these views in humans was often derived from statistical analyses of how various traits tended to run in families. But all too frequently, explanations of data were clouded by pre-existing, hereditarian assumptions.

Human Behavioral Genetics

The statistical study of inherited human (physical, mental, and behavioral) differences was pioneered by Galton ( 1869 ). Although at times Galton wrote that nature and nurture were so intertwined as to be inseparable, he nevertheless devised statistical methods to separate their effects. In the 1860s and 1870s, Galton published reports purporting to show how similarities in intellect (genius, talent, character, and eminence) in European lineages appeared to be a function of degree of relatedness. Galton considered, but dismissed, environmental explanations of his data, leading him to confirm his belief that nature was stronger than nurture.

Galton also introduced the use of twin studies to tease apart the relative impact of nature versus nurture, but the twin method he used was markedly different from later twin studies used by behavioral geneticists. Galton tracked the life history of twins who were judged to be very similar or very dissimilar near birth (i.e., by nature) to test the power of various postnatal environments (nurture) that might make them more or less similar over time. Here again, Galton concluded that nature overpowers nurture.

Similar pedigree (e.g., the Kallikak study; see Zenderland, 2001 ) and twin studies appeared in the early 1900s, but the first adoption study and the modern twin method (which compares monozygotic to dizygotic twin pairs) did not appear until the 1920s (Rende, Plomin, & Vandenberg, 1990 ). These reports led to a flurry of additional work on the inheritance of mental and behavioral traits over the next decade.

Behavioral genetic research peaked in the 1930s but rapidly lost prominence due in large part to its association with the eugenics movement (spearheaded by Galton) but also because of the rise and eventual hegemony of behaviorism and the social sciences in the United States. Behavioral genetics resurged in the 1960s with the rising tide of nativism in psychology, and returned to its 1930s-level prominence in the 1970s (McGue & Gottesman, 2015 ).

The resurgence brought with a new statistical tool: the heritability statistic. The origins of heritability trace back to early attempts to synthesize Mendelian genetics with biometrics by Ronald Fisher and others. This synthesis ushered in a new field of quantitative genetics and it marked a new way of thinking about nature and nurture. The shift was to no longer think about nature and nurture as causes of traits in individuals but as causes of variation in traits between populations of individuals. Eventually, heritability came to refer to the amount of variance in a population sample that could be statistically attributed to genetic variation in that sample. Kinship (especially twin) studies provided seemingly straightforward ways of partitioning variation in population trait attributes into genetic versus environmental sources.

Into the early 21st century , hundreds of behavioral genetic studies of personality, intelligence, and psychopathology were reported. With rare exceptions, these studies converge to argue for a pervasive influence of genetics on human psychological variation.

These studies have also fueled much controversy. Citing in part behavioral genetic research, the educational psychologist Arthur Jensen ( 1969 ) claimed that the differences in intelligence and educational achievement in the United States between black and white students appeared to have a strong genetic basis. He went on to assume that because these racial differences appeared hereditary, they were likely impervious to environmental (educational) intervention. His article fanned the embers of past eugenics practices and ignited fiery responses (e.g., Hirsch, 1975 ). The ensuing debates not only spawned a rethinking of intelligence and how to measure it, but they ushered in a more critical look at the methods and assumptions of behavioral genetics.

Challenges to Behavioral Genetics

Many of the early critiques of behavioral genetics centered on interpreting the heritability statistic commonly calculated in kinship (family, twin, and adoption) studies. Perhaps more so than any other statistic, heritability has been persistently misinterpreted by academics and laypersons alike (Lerner, 2002 ). Contrary to popular belief, heritability tells us nothing about the relative impact of genetic and environmental factors on the development of traits in individuals. It deals with accounting for trait variation between people, not the causes of traits within people. As a result, a high heritability does not indicate anything about the fixity of traits or their imperviousness to environmental influence (contra Jensen), and a low heritability does not indicate an absence of genetic influence on trait development. Worse still, heritability does not even indicate anything about the role of genetics in generating the differences between people.

Other challenges to heritability focused not on its interpretation but on its underlying computational assumptions. Most notably, heritability analyses assume that genetic and environmental contributions to trait differences are independent and additive. The interaction between genetic and environmental factors were dismissed a priori in these analyses. Studies of development, however, show that no factor (genes, hormones, parenting, schooling) operates independently, making it impossible to quantify how much of a given trait in a person is due to any causal factor. Thus heritability analyses are bound to be misleading because they are based on biologically implausible and logically indefensible assumptions about development (Gottlieb, 2003 ).

Aside from heritability, kinship studies have been criticized for not being able to disentangle genetic and environmental effects on variation. It had long been known that that in family (pedigree) studies, environmental and genetic factors are confounded. Twin and adoption studies seemed to provide unique opportunities to statistically disentangle these effects, but these studies are also deeply problematic in assumptions and methodology. There are numerous plausible environmental reasons for why monozygotic twin pairs could resemble each other more than dizygotic twin pairs or why adoptive children might more closely resemble their biological than their adoptive parents (Joseph & Ratner, 2013 ).

A more recent challenge to behavioral genetics came from an unlikely source. Advances in genomic scanning in the 21st century made it possible in a single study to correlate thousands of genetic polymorphisms with variation in the psychological profiles (e.g., intelligence, memory, temperament, psychopathology) of thousands of people. These “genome-wide association” studies seemed to have the power and precision to finally identify genetic contributions to heritability at the level of single nucleotides. Yet, these studies consistently found only very small effects.

The failure to find large effects came to be known as the “missing heritability” problem (Maher, 2008 ). To account for the missing heritability, some behavioral geneticists and molecular biologists asserted that important genetic polymorphisms remain unknown, they may be too rare to detect, and/or that current studies are just not well equipped to handle gene–gene interactions. These studies were also insensitive to epigenetic profiles (see the section on Behavioral Epigenetics), which deal with differences in gene expression. Even when people share genes, they may differ in whether those genes get expressed in their lifetimes.

But genome-wide association studies faced an even more problematic issue: Many of these studies failed to replicate (Lickliter & Honeycutt, 2015 ). For those who viewed heritability analyses as biologically implausible, the small effect sizes and failures to replicate in genome-wide association studies were not that surprising. The search for independent genetic effects was bound to fail, because genes simply do not operate independently during development.

Behavioral Epigenetics

Epigenetics was a term coined in the 1940s by the developmental biologist Conrad Waddington to refer to a new field of study that would examine how genetic factors interact with local environmental conditions to bring about the embryological development of traits. By the end of the 20th century , epigenetics came to refer to the study of how nongenetic, molecular mechanisms physically regulate gene expression patterns in cells and across cell lineages. The most-studied mechanisms involve organic compounds (e.g., methyl-groups) that physically bind to DNA or the surrounding proteins that package DNA. The addition or removal of these compounds can activate or silence gene transcription. Different cell types have different, stable epigenetic markings, and these markings are recreated during cell division so that cells so marked give rise to similar types of cells. Epigenetic changes were known to occur during developmental periods of cellular differentiation (e.g., during embryogenesis), but not until 2004 was it discovered that these changes can occur at other periods in the life, including after birth (Roth, 2013 )

Of interest to psychologists were reports that different behavioral and physiological profiles (e.g., stress reactivity) of animals were associated with different epigenetic patterns in the nervous system (Moore, 2015 ). Furthermore, these different epigenetic patterns could be established or modified by environmental factors (e.g., caregiving practices, training regimes, or environmental enrichment), and, under certain conditions, they remain stable over long periods of time (from infancy to adulthood).

Because epigenetic research investigates the physical interface between genes and environment, it represents an exciting advance in understanding the interaction of nature and nurture. Despite some warnings that the excitement over behavioral epigenetic research may be premature (e.g., Miller, 2010 ), for many psychologists, epigenetics underscores how development involves both nature and nurture.

For others, what is equally exciting is the additional evidence epigenetics provides to show that the genome is an interactive and regulated system. Once viewed as the static director of development buffered from environment influence, the genome is better described as a developing resource of the cell (Moore, 2015 ). More broadly, epigenetics also points to how development is not a genetically (or biologically) predetermined affair. Instead, epigenetics provides additional evidence that development is a probabilistic process, contingent upon factors internal and external to the organism. In this sense, epigenetics is well positioned to help dissolve the nature–nurture dichotomy.

Beyond Nature–Nurture

In the final decades of the 20th century , a position was articulated to move beyond the dichotomous nature–nurture framework. The middle-ground position on nature–nurture did not seem up to the task of explaining the origins of form, and it brought about more confusion than clarity. The back-and-forth (or balanced) pendulum between nature- and nurture-based positions throughout history had only gone in circles. Moving forward would require moving beyond such dichotomous thinking (Johnston, 1987 ).

The anti-dichotomy position, referred to as the Developmentalist tradition, was expressed in a variety of systems-based, metatheoretical approaches to studying development, all of which extended the arguments against nature–nurture expressed earlier by Kuo and Lehrman. The central problem with all nativist claims according to Developmentalists is a reliance on preformationism (or predeterminism).

The problem with preformationism, they argue, besides issues of evidence, is that it is an anti-developmental mindset. It presumes the existence of the very thing(s) one wishes to explain and, consequently, discourages developmental analyses. To claim that some knowledge is innate effectively shuts down research on the developmental origins of that knowledge. After all, why look for the origins of conceptual knowledge if that knowledge is there all along? Or why search for any experiential contributions to innate behaviors if those behaviors by definition develop independently of experience? In the words of Developmentalists Thelen and Adolph ( 1992 ), nativism “leads to a static science, with no principles for understanding change or for confronting the ultimate challenge of development, the source of new forms in structure and function” (p. 378).

A commitment to maturational theory is likely one of the reasons why studies of motor development remained relatively dormant for decades following its heyday in the 1930–1940s (Thelen, 2000 ). Likewise, a commitment to maturational theory also helps explain the delay in neuroscience to examine how the brain physically changes in response to environmental conditions, a line of inquiry that only began in the 1960s.

In addition to the theoretical pitfalls of nativism, Developmentalists point to numerous studies that show how some seemingly native behaviors and innate constraints on learning are driven by the experiences of animals. For example, the comparative psychologist Gilbert Gottlieb ( 1971 ) showed that newly hatched ducklings display a naïve preference for a duck maternal call over a (similarly novel) chicken maternal call (Gottlieb, 1971 ), even when duck embryos were repeatedly exposed to the chicken call prior to hatching (Gottlieb, 1991 ). It would be easy to conclude that ducklings have an innate preference to approach their own species call and that they are biologically constrained (contraprepared) in learning a chicken call. However, Gottlieb found that the naïve preference for the duck call stemmed from exposure to the duck embryos’ own (or other) vocalizations in the days before hatching (Gottlieb, 1971 ). Exposure to these vocalizations not only made duck maternal calls more attractive, but it hindered the establishment of a preference for heterospecific calls. When duck embryos were reared in the absence of the embryonic vocalizations (by devocalizing embryos in ovo ) and exposed instead to chicken maternal calls, the newly hatched ducklings preferred chicken over duck calls (Gottlieb, 1991 ). These studies clearly showed how seemingly innate, biologically based preferences and constraints on learning derived from prenatal sensory experiences.

For Developmentalists, findings like these suggest that nativist explanations of any given behavior are statements of ignorance about how that behavior actually develops. As Kuo and Lehrman made clear, nativist terms are labels, not explanations. Although such appeals are couched in respectable, scientific language (e.g., “X is due to maturation, genes, or heredity”), they argue it would be more accurate simply to say that “We don’t know what causes X” or that “X is not due to A, B, or C.” Indeed, for Developmentalists, the more we unpack the complex dynamics about how traits develop, the less likely we are to use labels like nature or nurture (Blumberg, 2005 ).

On the other hand, Developmentalists recognize that labeling a behavior as “learned” also falls short as an explanatory construct. The empiricist position that knowledge or behavior is learned does not adequately take into account that what is learned and how easily something is learned depends on (a) the physiological and developmental status of the person, (b) the nature of the surrounding physical and social context in which learning takes place, and the (c) experiential history of the person. The empiricist tendency to say “X is learned or acquired through experience” can also short-circuit developmental analyses in the same way as nativist claims.

Still, Developmentalists appreciate that classifying behaviors can be useful. For example, the development of some behaviors may be more robust, reliably emerging across a range of environments and/or remaining relatively resistant to change, whereas others are more context-specific and malleable. Some preferences for stimuli require direct experience with those stimuli. Other preferences require less obvious (indirect) types of experiences. Likewise, it can still be useful to describe some behaviors in the ways shown in Table 1 . Developmentalists simply urge psychologists to resist the temptation to treat these behavioral classifications as implying different kinds of explanations (Johnston, 1987 ).

Rather than treat nature and nurture as separate developmental sources of causation (see Figure 1 ), Developmentalists argue that a more productive way of thinking about nature–nurture is to reframe the division as that between product and process (Lickliter & Honeycutt, 2015 ). The phenotype or structure (one’s genetic, epigenetic, anatomical, physiological, behavioral, and mental profile) of an individual at any given time can be considered one’s “nature.” “Nurture” then refers to the set of processes that generate, maintain, and transform one’s nature (Figure 2 ). These processes involve the dynamic interplay between phenotypes and environments.

Figure 2. The developmentalist alternative view of nature–nurture as product–process. Developmentalists view nature and nurture not as separate sources of causation in development (see Figure 1 ) but as a distinction between process (nurture) and product (nature).

It is hard to imagine any set of findings that will end debates about the roles of nature and nurture in human development. Why? First, more so than other assumptions about human development, the nature–nurture dichotomy is deeply entrenched in popular culture and the life sciences. Second, throughout history, the differing positions on nature and nurture were often driven by other ideological, philosophical, and sociopolitical commitments. Thus the essential source of tension in debates about nature–nurture is not as much about research agendas or evidence as about basic differences in metatheoretical positions (epistemological and ontological assumptions) about human behavior and development (Overton, 2006 ).

• Amundson, R. (2000). Embryology and evolution 1920–1960: Worlds apart? History and Philosophy of the Life Sciences , 22 , 335–352.
• Amundson, R. (2005). The changing role of the embryo in evolutionary thought: Roots of evo-devo . New York, NY: Cambridge University Press.
• Blumberg, M. S. (2005). Basic instinct: The genesis of novel behavior . New York, NY: Thunder’s Mouth Press.
• Breland, K. , & Breland, M. (1961). The misbehavior of organisms. American Psychologist , 16 , 681–684.
• Burkhardt, R. (2005). Patterns of behavior: Konrad Lorenz, Niko Tinbergen and the founding of ethology . Chicago, IL: University of Chicago Press.
• Burnham, J. C. (1972). Instinct theory and the German reaction to Weismannism. Journal of the History of Biology , 5 , 321–326.
• Carmichael, L. (1925). Heredity and environment: Are they antithetical? The Journal of Abnormal and Social Psychology , 20 (3), 245–260.
• Chomsky, N. (1959). A review of B. F. Skinner’s verbal behavior. Language , 35 , 26–57.
• Chomsky, N. (1965). Aspects of the theory of syntax . Cambridge, MA: MIT Press.
• Connolly, K. (1972). Learning and the concept of critical periods in infancy. Developmental Medicine & Child Neurology , 14 (6), 705–714.
• Cook, G. M. (1999). Neo-Lamarckian experimentalism in America: Origins and consequences. Quarterly Review of Biology , 74 , 417–437.
• Cowan, R. S. C. (2016). Commentary: Before Weismann and germplasm there was Galton and eugenics: The biological and political meaning of the inheritance of acquired characteristics in the late 19th century . International Journal of Epidemiology , 45 , 15–20.
• Cravens, H. , & Burnham, J. C. (1971). Psychology and evolutionary naturalism in American thought, 1890–1940. American Quarterly , 23 , 635–657.
• Diamond, S. (1971). Gestation of the instinct concept. History of the Behavioral Sciences , 7 (4), 323–336.
• Domjan, M. , & Galef, B. G. (1983). Biological constraints on instrumental and classical conditioning: Retrospect and prospect. Animal Learning & Behavior , 11 (2), 151–161.
• Dunlap, K. (1919). Are there any instincts? Journal of Abnormal Psychology , 14 , 307–311.
• Galton, F. (1869). Hereditary genius . London, U.K.: Macmillan.
• Garcia, J. , & Koelling, R. A. (1966). Relation of cue to consequence in avoidance learning. Psychonomics , 4 (1), 123–124.
• Gottlieb, G. (1971). Development of species identification in birds . Chicago, IL: University of Chicago Press.
• Gottlieb, G. (1991). Experiential canalization of behavioral development: Results. Developmental Psychology , 27 (1), 35–39.
• Gottlieb, G. (1992). Individual development and evolution: The genesis of novel behavior . New York, NY: Oxford University Press.
• Gottlieb, G. (2003). On making behavioral genetics truly developmental. Human Development , 46 , 337–355.
• Gould, J. L. , & Marler, P. (1987). Learning by instinct. Scientific American , 256 (1), 74–85.
• Gould, S. J. (1996). The mismeasure of man (2nd ed.). New York, NY: Norton.
• Gray, P. H. (1967). Spalding and his influence on research in developmental behavior. Journal of the History of the Behavioral Sciences , 3 , 168–179.
• Griffiths, P. E. (2008). Ethology, sociobiology, and evolutionary psychology. In S. Sarkar & A. Plutnsky (Eds.), A companion to the philosophy of biology (pp. 393–414). New York, NY: Blackwell.
• Harwood, J. (1985). Geneticists and the evolutionary synthesis in interwar Germany. Annals of Science , 42 , 279–301.
• Herrnstein, R. J. (1972). Nature as nurture: Behaviorism and the instinct doctrine. Behaviorism , 1 (1), 23–52.
• Heyes, C. (2014). False belief in infancy: A fresh look. Developmental Science , 17 (5), 647–659.
• Hirsch, J. (1975). Jensenism: The bankruptcy of “science” without scholarship. Educational Theory , 25 , 3–27.
• Hoffman, H. , & Spear, N. E. (1988). Ontogenetic differences in conditioning of an aversion to a gustatory CS with a peripheral US. Behavioral and Neural Biology , 50 , 16–23.
• Honeycutt, H. (2011). The “enduring mission” of Zing-Yang Kuo to eliminate the nature–nurture dichotomy in psychology. Developmental Psychobiology , 53 (4), 331–342.
• Jaynes, J. , & Woodward, W. (1974). In the shadow of the enlightenment. II. Reimarus and his theory of drives. Journal of the History of the Behavioral Sciences , 10 , 144–159.
• Jensen, A. (1969). How much can we boost IQ and scholastic achievement. Harvard Educational Review , 39 , 1–123.
• Johnston, T. (1981). Contrasting approaches to a theory of learning. Behavioral and Brain Sciences , 4 , 125–173.
• Johnston, T. (1987). The persistence of dichotomies in the study of behavior. Developmental Review , 7 , 149–172.
• Johnston, T. (1995). The influence of Weismann’s germ-plasm theory on the distinction between learned and innate behavior. Journal of the History of the Behavioral Sciences , 31 , 115–128.
• Jones, S. (2017). Can newborn infants imitate? Wiley Interdisciplinary Reviews: Cognitive Science , 8 , e1410.
• Joseph, J. , & Ratner, C. (2013). The fruitless search for genes in psychiatry and psychology: Time to reexamine a paradigm. In S. Krimsky & J. Gruber (Eds.), Genetic explanations: Sense and nonsense (pp. 94–106). Cambridge, MA: Harvard University Press.
• Keller, E. F. (2010). The mirage of space between nature and nurture . Durham, NC: Duke University Press.
• Koops, W. (2015). No developmental psychology without recapitulation theory . European Journal of Developmental Psychology , 12 (6), 630–639.
• Kuo, Z. Y. (1930). The genesis of the cat’s response to the rat. Journal of Comparative Psychology , 11 , 1–36.
• Lehrman, D. S. (1953). A critique of Konrad Lorenz’s theory of instinctive behavior. Quarterly Review of Biology , 28 , 337–363.
• Lerner, R. (2002). Concepts and theories of human development (3rd ed.). Mahwah, NJ: Erlbaum.
• Lickliter, R. , & Honeycutt, H. (2015). Biology, development and human systems . In W. Overton & P. C. M. Molenaar (Eds.), Handbook of child psychology and developmental science . Vol. 1: Theory and method (7th ed., pp. 162–207). Hoboken, NJ: Wiley.
• Logan, C. A. , & Johnston, T. D. (2007). Synthesis and separation in the history of “nature” and “nurture.” Developmental Psychobiology , 49 (8), 758–769.
• Loison, L. (2011). French roots of French neo-Lamarckisms,1879–1985 . Journal of the History of Biology , 44 , 713–744.
• Maher, B. (2008). Personal genomes: The case of the missing heritability . Nature , 456 , 18–21.
• McGue, M. , & Gottesman, I. I. (2015). Behavior genetics . In R. L. Cautin & S. O. Lilienfeld (Eds.), The encyclopedia of clinical psychology (Vol. 1). Chichester, U.K.: Wiley Blackwell.
• Meloni, M. (2016). The transcendence of the social: Durkheim, Weismann and the purification of sociology . Frontiers in Sociology , 1 , 1–13.
• Michel, G. F. , & Tyler, A. N. (2005). Critical period: A history of transition of questions of when, to what, to how . Developmental Psychobiology , 46 (3), 156–162.
• Miller, G. (2010).The seductive allure of behavioral epigenetics. Science , 329 (5987), 24–27.
• Moore, D. S. (2015). The developing genome. An introduction to behavioral epigenetics . New York, NY: Oxford University Press
• Morgan, C. L. (1896). Habit and instinct . New York, NY: Edward Arnold.
• Muller-Wille, S. , & Rheinberger, H.-J. (2012). A cultural history of heredity . Chicago, IL: University of Chicago Press.
• Ohman, A. , Fredrikson, M. , Hugdahl, K. , & Rimmö, P.A. (1976). The premise of equipotentiality in human classical conditioning: Conditioned electrodermal responses to potentially phobic stimuli. Journal of Experimental Psychology: General , 105 (4), 313–337.
• Overton, W. F. (2006). Developmental psychology: Philosophy, concepts, methodology. In R. Lerner (Ed.), Handbook of child psychology: Vol. 1. Theoretical models of human development (pp. 18–88). New York, NY: Wiley.
• Oyama, S. (1979). The concept of the sensitive period in developmental studies. Merrill-Palmer Quarterly , 25 (2), 83–103.
• Piaget, J. (1971). Biology and knowledge: An essay on the relation between organic regulations and cognitive processes . Chicago, IL: University of Chicago Press.
• Pinker, S. (1995). The language instinct: How the mind creates language . London, U.K.: Penguin.
• Rende, R. D. , Plomin, R. , & Vandenberg, S. G. (1990). Who discovered the twin method? Behavioral Genetics , 20 (2), 277–285.
• Renwick, C. (2011). From political economy to sociology: Francis Galton and the social-scientific origins of eugenics . British Journal for the History of Science , 44 , 343–369.
• Richards, R. J. (1987). Darwin and the emergence of evolutionary theories of mind and behavior . Chicago, IL: University of Chicago Press.
• Robinson, G. E. , & Barron, A. B. (2017). Epigenetics and the evolution of instincts. Science , 356 (6333), 26–27.
• Roth, T. L. (2013). Epigenetic mechanisms in the development of behavior: Advances, challenges, and future promises of a new field . Development and Psychopathology , 25 , 1279–1291.
• Samet, J. , & Zaitchick, D. (2017). Innateness and contemporary theories of cognition . In E. N. Zalta (Ed.), The Stanford encyclopedia of philosophy . Stanford, CA: Stanford University.
• Segerstrale, U. (2000). Defenders of the truth: The battle for science in the sociobiology debate and beyond . New York, NY: Oxford University Press.
• Simion, F. , & Di Giorgio, E. (2015). Face perception and processing in early infancy: Inborn predispositions and developmental changes . Frontiers in Psychology , 6 , 969.
• Simpson, T. , Carruthers, P. , Laurence, S. , & Stich, S. (2005). Introduction: Nativism past and present . In P. Carruthers , S. Laurence , & S. Stich (Eds.), The innate mind: Structure and contents (pp. 3–19). New York, NY: Oxford University Press.
• Spelke, E. , & Kinzler, K. D. (2007). Core knowledge . Developmental Science , 10 (1), 89–96.
• Spencer, J. P. , Samuelson, L. K. , Blumberg, M. S. , McMurray, R. , Robinson, S. R. , & Tomblin, J. B. (2009). Seeing the world through a third eye: Developmental systems theory looks beyond the nativist-empiricist debate. Child Development Perspectives , 3 , 103–105.
• Thelen, E. (2000). Motor development as foundation and future of developmental psychology. International Journal of Behavioral Development , 24 (4), 385–397.
• Thelen, E. , & Adolph, K. E. (1992). Arnold L. Gesell: The paradox of nature and nurture. Developmental Psychology , 28 (3), 368–380.
• Tinbergen, N. (1963). On the aims and methods of ethology. Zeitschrift für Tierpsychologie , 20 , 410–433.
• Tomasello, M. T. (1995). Language is not an instinct. Cognitive Development , 10 , 131–156.
• Winther, R. G. (2001). Weismann on germ-plasm variation. Journal of the History of Biology , 34 , 517–555.
• Witty, P. A. , & Lehman, H. C. (1933). The instinct hypothesis versus the maturation hypothesis. Psychological Review , 40 (1), 33–59.
• Wyman, R. J. (2005). Experimental analysis of nature–nurture. Journal of Experimental Zoology , 303 , 415–421.
• Zenderland, L. (2001). Measuring minds. Henry Herbert Goddard and the origins of American intelligence testing . New York, NY: Cambridge University Press.

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3.6: The Nature-Nurture Question

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This page is a draft and under active development. Please forward any questions, comments, and/or feedback to the ASCCC OERI ( [email protected] ).

• Kenenth A. Koenigshofer
• ASCCC Open Educational Resources Initiative (OERI)

Learning Objectives

• Discuss the nature–nurture debate and why the problem fascinates us.
• Explain why nature–nurture questions are difficult to study empirically.
• Describe the major research designs that can be used to study nature–nurture questions.
• Discuss the complexities of nature–nurture and why questions that seem simple turn out not to have simple answers.
• Explain the main claim of sociobiology and the reasons why it is controversial.

Overview 

People have a deep intuition about what has been called the “nature–nurture question.” Some aspects of our behavior feel as though they originate in our genetic makeup, while others feel like the result of our upbringing or our own hard work. The scientific field of behavior genetics attempts to study these differences empirically, either by examining similarities among family members with different degrees of genetic relatedness, or, more recently, by studying differences in the DNA of people with different behavioral traits. The scientific methods that have been developed are ingenious, but often inconclusive. Many of the difficulties encountered in the empirical science of behavior genetics turn out to be conceptual, and our intuitions about nature and nurture get more complicated the harder we think about them. In the end, it is an oversimplification to ask how “genetic” some particular behavior is. Genes and environments always combine to produce behavior, and the real science is in the discovery of how they combine for a given behavior.

Genes and Environment

It may seem obvious that we are born with certain characteristics while others are acquired, and yet in the history of psychology, no other question has caused so much controversy and offense: We are so concerned with nature–nurture because our very sense of moral character seems to depend on it. While we may admire the athletic skills of a great basketball player, we think of his height as simply a gift, a payoff in the “genetic lottery.” For the same reason, no one blames a short person for his height or someone’s congenital disability on poor decisions: To state the obvious, it’s “not their fault.” But we do praise the concert violinist (and perhaps her parents and teachers as well) for her dedication, just as we condemn cheaters, slackers, and bullies for their bad behavior.

The problem is, most human characteristics aren’t usually as clear-cut as height or instrument-mastery, affirming our nature–nurture expectations strongly one way or the other. In fact, even the great violinist might have some inborn qualities—perfect pitch, or long, nimble fingers—that support and reward her hard work. And the basketball player might have eaten a diet while growing up that promoted his genetic tendency for being tall. When we think about our own qualities, they seem under our control in some respects, yet beyond our control in others. And often the traits that don’t seem to have an obvious cause are the ones that concern us the most and are far more personally significant. What about how much we drink or worry? What about our honesty, or religiosity, or sexual orientation? They all come from that uncertain zone, neither fixed by nature nor totally under our own control.

One major problem with answering nature-nurture questions about people is, how do you set up an experiment? In nonhuman animals, there are relatively straightforward experiments for tackling nature–nurture questions. Say, for example, you are interested in aggressiveness in dogs. You want to test for the more important determinant of aggression: being born to aggressive dogs or being raised by them. You could mate two aggressive dogs—angry Chihuahuas—together, and mate two nonaggressive dogs—happy beagles—together, then switch half the puppies from each litter between the different sets of parents to raise. You would then have puppies born to aggressive parents (the Chihuahuas) but being raised by nonaggressive parents (the Beagles), and vice versa, in litters that mirror each other in puppy distribution. The big questions are: Would the Chihuahua parents raise aggressive beagle puppies? Would the beagle parents raise nonaggressive Chihuahua puppies? Would the puppies’ nature win out, regardless of who raised them? Or... would the result be a combination of nature and nurture? Much of the most significant nature–nurture research has been done in this way (Scott & Fuller, 1998), and animal breeders have been doing it successfully for thousands of years. In fact, it is fairly easy to breed animals for behavioral traits. 

For example, Koenigshofer and Nachman (1974) selectively bred rats for their ability to learn taste aversions.  When a novel flavor such as sugar water is followed by mild poisoning by injection 15 minutes later, rats learn to avoid that flavor in the future after a single pairing of flavor and illness (see section 10.2, Specialized Forms of Learning).  However, rats varied in how well they learned aversion to the sugar water.  A few rats when tested 4 days later showed that they had learned a strong aversion (they consumed very little of the flavor that had been previously followed by poison-induced illness) while a few others learned a weak aversion (they consumed a large amount of the flavor previously paired with illness), while most of the conditioned rats learned a moderate aversion to the flavor previously paired with illness (they consumed an intermediate amount of the flavor previously paired with poison-induced illness).  After this first phase of the experiment, rats were selectively bred. Those males and females that learned a strong aversion were bred together, while male and female rats that learned a weak aversion were bred together.  Those that learned an intermediate aversion were not bred.  This process, involving the pairing of taste and illness followed by selective breeding for strong or weak learning, was repeated for several generations.  After just five generations of this selective breeding procedure for taste aversion learning, two strains of rats resulted, strong learners and weak learners, which showed no overlap at all in the strength of taste aversion that they learned after just five generations of selective breeding.  The worst learners of the strong learner strain were still much better learners than the best learners of the weak learner strain.  The effect of selective breeding in these experiments was greater than the effects of brain lesions on learning ability.  This suggests that learning abilities have a significant genetic component--a proposition that is consistent with the hypothesis that at least some differences among humans in learning ability involve genetic differences.  That learning abilities have a genetic components suggests that learning abilities have evolved over time by selection (i.e. natural selection).  If learning is an evolved genetic trait, how can any behavioral trait, even those that are learned, not have a genetic component?

Although we can experiment with animals, with people, however, we can’t assign babies to parents at random, or select parents with certain behavioral characteristics to mate, merely in the interest of science (though history does include horrific examples of such practices, in misguided attempts at “eugenics,” the shaping of human characteristics through intentional breeding). In typical human families, children’s biological parents raise them, so it is very difficult to know whether children act like their parents due to genetic (nature) or environmental (nurture) reasons. Nevertheless, despite our restrictions on setting up human-based experiments, we do see real-world examples of nature-nurture at work in the human sphere—though they only provide partial answers to our questions.

The science of how genes and environments work together to influence behavior is called behavioral genetics. The easiest opportunity we have to observe this is the adoption study . When children are put up for adoption, the parents who give birth to them are no longer the parents who raise them. This setup isn’t quite the same as the experiments with dogs (children aren’t assigned to random adoptive parents in order to suit the particular interests of a scientist) but adoption still tells us some interesting things, or at least confirms some basic expectations. For instance, if the biological child of tall parents were adopted into a family of short people, do you suppose the child’s growth would be affected? What about the biological child of a Spanish-speaking family adopted at birth into an English-speaking family? What language would you expect the child to speak? And what might these outcomes tell you about the difference between height and language in terms of nature-nurture?  

Another option for observing nature-nurture in humans involves twin studies . There are two types of twins: monozygotic (MZ) and dizygotic (DZ) . Monozygotic twins, also called “identical” twins, result from a single zygote (fertilized egg) and have the same DNA. They are essentially clones. Dizygotic twins, also known as “fraternal” twins, develop from two zygotes (fertilized eggs) and share 50% of their DNA. Fraternal twins are ordinary siblings who happen to have been born at the same time. To analyze nature–nurture using twins, we compare the similarity of MZ and DZ pairs. Sticking with the features of height and spoken language, let’s take a look at how nature and nurture apply: Identical twins, unsurprisingly, are almost perfectly similar for height. The heights of fraternal twins, however, are like any other sibling pairs: more similar to each other than to people from other families, but hardly identical. This contrast between twin types gives us a clue about the role genetics plays in determining height. Now consider spoken language. If one identical twin speaks Spanish at home, the co-twin with whom she is raised almost certainly does too. But the same would be true for a pair of fraternal twins raised together. In terms of spoken language, fraternal twins are just as similar as identical twins, so it appears that the genetic match of identical twins doesn’t make much difference.  What language you speak is determined by environment; having more genes in common (MZ vs DZ) doesn't make any difference.

Twin and adoption studies are two instances of a much broader class of methods for observing nature-nurture called quantitative genetics , the scientific discipline in which similarities among individuals are analyzed based on how biologically related they are. We can do these studies with siblings and half-siblings, cousins, twins who have been separated at birth and raised separately (Bouchard, Lykken, McGue, & Segal, 1990 ; such twins are very rare and play a smaller role than is commonly believed in the science of nature–nurture), or with entire extended families (see Plomin, DeFries, Knopik, & Neiderhiser, 2012 , for a complete introduction to research methods relevant to nature–nurture).

For better or for worse, contentions about nature–nurture have intensified because quantitative genetics produces a number called a heritability coefficient , varying from 0 to 1, that is meant to provide a single measure of genetics’ influence on a trait. In a general way, a heritability coefficient measures how strongly differences among individuals are related to differences among their genes . But beware: Heritability coefficients, although simple to compute, are deceptively difficult to interpret. Nevertheless, numbers that provide simple answers to complicated questions tend to have a strong influence on the human imagination, and a great deal of time has been spent discussing whether the heritability of intelligence or personality or depression is equal to one number or another.

One reason nature–nurture continues to fascinate us so much is that we live in an era of great scientific discovery in genetics, comparable to the times of Copernicus, Galileo, and Newton, with regard to astronomy and physics. Every day, it seems, new discoveries are made, new possibilities proposed. When Francis Galton first started thinking about nature–nurture in the late-19th century he was very influenced by his cousin, Charles Darwin, but genetics per se was unknown. Mendel’s famous work with peas, conducted at about the same time, went undiscovered for 20 years; quantitative genetics was developed in the 1920s; DNA was discovered by Watson and Crick in the 1950s; the human genome was completely sequenced at the turn of the 21st century; and we are now on the verge of being able to obtain the specific DNA sequence of anyone at a relatively low cost. No one knows what this new genetic knowledge will mean for the study of nature–nurture, but as we will see in the next section, answers to nature–nurture questions have turned out to be far more difficult and mysterious than anyone imagined.

What have we learned about nature-nurture?

It would be satisfying to be able to say that nature–nurture studies have given us conclusive and complete evidence about where traits come from, with some traits clearly resulting from genetics and others almost entirely from environmental factors, such as childrearing practices and personal will; but that is not the case. Instead, everything has turned out to have some footing in genetics . The more genetically-related people are, the more similar they are—for everything: height, weight, intelligence, personality, mental illness, etc. Sure, it seems like common sense that some traits have a genetic bias. For example, adopted children resemble their biological parents even if they have never met them, and identical twins are more similar to each other than are fraternal twins. And while certain psychological traits, such as personality or mental illness (e.g., schizophrenia), seem reasonably influenced by genetics, it turns out that the same is true for political attitudes, how much television people watch (Plomin, Corley, DeFries, & Fulker, 1990), and whether or not they get divorced (McGue & Lykken, 1992).

It may seem surprising, but genetic influence on behavior is a relatively recent discovery. In the middle of the 20th century, psychology was dominated by the doctrine of behaviorism, which held that behavior could only be explained in terms of environmental factors. Psychiatry concentrated on psychoanalysis, which probed for roots of behavior in individuals’ early life-histories. The truth is, neither behaviorism nor psychoanalysis is incompatible with genetic influences on behavior, and neither Freud nor Skinner was naive about the importance of organic processes in behavior. Nevertheless, in their day it was widely thought that children’s personalities were shaped entirely by imitating their parents’ behavior, and that schizophrenia was caused by certain kinds of “pathological mothering.” Whatever the outcome of our broader discussion of nature–nurture, the basic fact that the best predictors of an adopted child’s personality or mental health are found in the biological parents he or she has never met, rather than in the adoptive parents who raised him or her, presents a significant challenge to purely environmental explanations of personality or psychopathology. The message is clear: You can’t leave genes out of the equation. But keep in mind, no behavioral traits are completely inherited, so you can’t leave the environment out altogether, either.

Trying to untangle the various ways nature-nurture influences human behavior can be messy, and often common-sense notions can get in the way of good science. One very significant contribution of behavioral genetics that has changed psychology for good can be very helpful to keep in mind: When your subjects are biologically-related, no matter how clearly a situation may seem to point to environmental influence, it is never safe to interpret a behavior as wholly the result of nurture without further evidence. For example, when presented with data showing that children whose mothers read to them often are likely to have better reading scores in third grade, it is tempting to conclude that reading to your kids out loud is important to success in school; this may well be true, but the study as described is inconclusive, because there are genetic as well as environmental pathways between the parenting practices of mothers and the abilities of their children. This is a case where “correlation does not imply causation,” as they say. To establish that reading aloud causes success, a scientist can either study the problem in adoptive families (in which the genetic pathway is absent) or by finding a way to randomly assign children to oral reading conditions.

The outcomes of nature–nurture studies have fallen short of our expectations (of establishing clear-cut bases for traits) in many ways. The most disappointing outcome has been the inability to organize traits from more-to less-genetic. As noted earlier, everything has turned out to be at least somewhat heritable (passed down), yet nothing has turned out to be absolutely heritable , and there hasn’t been much consistency as to which traits are more heritable and which are less heritable once other considerations (such as how accurately the trait can be measured) are taken into account (Turkheimer, 2000 ). The problem is conceptual: The heritability coefficient, and, in fact, the whole quantitative structure that underlies it, does not match up with our nature–nurture intuitions. We want to know how “important” the roles of genes and environment are to the development of a trait, but in focusing on “important” maybe we’re emphasizing the wrong thing. First of all, genes and environment are both crucial to every trait; without genes the environment would have nothing to work on, and too, genes cannot develop in a vacuum. Even more important, because nature–nurture questions look at the differences among people, the cause of a given trait depends not only on the trait itself, but also on the differences in that trait between members of the group being studied.

The classic example of the heritability coefficient defying intuition is the trait of having two arms. No one would argue against the development of arms being a biological, genetic process . But fraternal twins are just as similar for “two-armedness” as identical twins, resulting in a heritability coefficient of zero for the trait of having two arms. Normally, according to the heritability model, this result (coefficient of zero) would suggest all nurture, no nature, but we know that’s not the case. The reason this result is not a tip-off that arm development is less genetic than we imagine is because people do not vary in the genes related to arm development —which essentially upends the heritability formula. In fact, in this instance, the opposite is likely true: the extent that people differ in arm number is likely the result of accidents and, therefore, environmental. For reasons like these, we always have to be very careful when asking nature–nurture questions, especially when we try to express the answer in terms of a single number. The heritability of a trait is not simply a property of that trait, but a property of the trait in a particular context of relevant genes and environmental factors.

Another issue with the heritability coefficient is that it divides traits’ determinants into two portions—genes and environment—which are then calculated together for the total variability. This is a little like asking how much of the experience of a symphony comes from the horns and how much from the strings; the ways instruments or genes integrate is more complex than that. It turns out to be the case that, for many traits, genetic differences affect behavior under some environmental circumstances but not others—a phenomenon called gene-environment interaction , or G x E. In one well-known example, Caspi et al. (2002 ) showed that among maltreated children, those who carried a particular allele of the MAOA gene showed a predisposition to violence and antisocial behavior, while those with other alleles did not. Whereas, in children who had not been maltreated, the gene had no effect. Making matters even more complicated are very recent studies of what is known as epigenetics (see module, “Epigenetics” http://noba.to/37p5cb8v ), a process in which the DNA itself is modified by environmental events, and those genetic changes transmitted to children.

Some common questions about nature–nurture are, how susceptible is a trait to change, how malleable is it, and do we “have a choice” about it? These questions are much more complex than they may seem at first glance. For example, phenylketonuria is an inborn error of metabolism caused by a single gene; it prevents the body from metabolizing phenylalanine. Untreated, it causes intellectual disability and death. But it can be treated effectively by a straightforward environmental intervention: avoiding foods containing phenylalanine. Height seems like a trait firmly rooted in our nature and unchangeable, but the average height of many populations in Asia and Europe has increased significantly in the past 100 years, due to changes in diet and the alleviation of poverty. Even the most modern genetics has not provided definitive answers to nature–nurture questions. When it was first becoming possible to measure the DNA sequences of individual people, it was widely thought that we would quickly progress to finding the specific genes that account for behavioral characteristics, but that hasn’t happened. There are a few rare genes that have been found to have significant (almost always negative) effects, such as the single gene that causes Huntington’s disease, or the Apolipoprotein gene that causes early onset dementia in a small percentage of Alzheimer’s cases. Aside from these rare genes of great effect, however, the genetic impact on behavior is broken up over many genes, each with very small effects. For most behavioral traits, the effects are so small and distributed across so many genes that we have not been able to catalog them in a meaningful way. In fact, the same is true of environmental effects. We know that extreme environmental hardship causes catastrophic effects for many behavioral outcomes, but fortunately extreme environmental hardship is very rare. Within the normal range of environmental events, those responsible for differences (e.g., why some children in a suburban third-grade classroom perform better than others) are much more difficult to grasp.

The difficulties with finding clear-cut solutions to nature–nurture problems bring us back to the other great questions about our relationship with the natural world: the mind-body problem and free will. Investigations into what we mean when we say we are aware of something reveal that consciousness is not simply the product of a particular area of the brain, nor does choice turn out to be an orderly activity that we can apply to some behaviors but not others. So it is with nature and nurture: What at first may seem to be a straightforward matter, able to be indexed with a single number, becomes more and more complicated the closer we look. The many questions we can ask about the intersection among genes, environments, and human traits—how sensitive are traits to environmental change, and how common are those influential environments; are parents or culture more relevant; how sensitive are traits to differences in genes, and how much do the relevant genes vary in a particular population; does the trait involve a single gene or a great many genes; is the trait more easily described in genetic or more-complex behavioral terms?—may have different answers, and the answer to one tells us little about the answers to the others.

It is tempting to predict that the more we understand the wide-ranging effects of genetic differences on all human characteristics—especially behavioral ones—our cultural, ethical, legal, and personal ways of thinking about ourselves will have to undergo profound changes in response. Perhaps criminal proceedings will consider genetic background. Parents, presented with the genetic sequence of their children, will be faced with difficult decisions about reproduction. These hopes or fears are often exaggerated. In some ways, our thinking may need to change—for example, when we consider the meaning behind the fundamental American principle that all men are created equal. Human beings differ, and like all evolved organisms they differ genetically. The Declaration of Independence predates Darwin and Mendel, but it is hard to imagine that Jefferson—whose genius encompassed botany as well as moral philosophy—would have been alarmed to learn about the genetic diversity of organisms. One of the most important things modern genetics has taught us is that almost all human behavior is too complex to be nailed down, even from the most complete genetic information, unless we’re looking at identical twins. The science of nature and nurture has demonstrated that genetic differences among people are vital to human moral equality, freedom, and self-determination, not opposed to them. As Mordecai Kaplan said about the role of the past in Jewish theology, genetics gets a vote, not a veto, in the determination of human behavior. We should indulge our fascination with nature–nurture while resisting the temptation to oversimplify it.

Outside Resources

Adoption study :  A behavior genetic research method that involves comparison of adopted children to their adoptive and biological parents.

Discussion Questions

• Is your personality more like one of your parents than the other? If you have a sibling, is his or her personality like yours? In your family, how did these similarities and differences develop? What do you think caused them?
• Can you think of a human characteristic for which genetic differences would play almost no role? Defend your choice.
• Do you think the time will come when we will be able to predict almost everything about someone by examining their DNA on the day they are born?
• Identical twins are more similar than fraternal twins for the trait of aggressiveness, as well as for criminal behavior. Do these facts have implications for the courtroom? If it can be shown that a violent criminal had violent parents, should it make a difference in culpability or sentencing?

Sociobiology

Sociobiology is an interdisciplinary science originally popularized by social insect researcher E.O. Wilson in the 1970s. Wilson defined the science as “the extension of population biology and evolutionary theory to social organization.” The main thrust of sociobiology is that animal and human behavior, including aggressiveness and other social interactions, can be explained almost solely in terms of genetics and natural selection (Wilson, 1975).

This science is controversial; some have criticized the approach for ignoring the environmental effects on behavior. This is another example of the “nature versus nurture” debate of the role of genetics versus the role of environment in determining an organism’s characteristics.

Sociobiology also links genes with behaviors and has been associated with “biological determinism,” the belief that all behaviors are hardwired into our genes. No one disputes that certain behaviors can be inherited and that natural selection plays a role in their organization. However, it is the application of such principles to human behavior that ruffles feathers and sparks this controversy, which remains active today.

• Sociobiology argues that all animal and human behavior, including aggressiveness and other social interactions, can be explained almost solely in terms of genetics and natural selection.
• Sociobiology is controversial: some have criticized the approach for ignoring the environmental effects on behavior and for being similar to “biological determinism,” or the belief that all behaviors are hardwired into our genes.
• biological determinism : also known as genetic determinism is the belief that most human traits, physical and psychological, are innate and determined by genes.
• sociobiology : the science that applies the principles of evolutionary biology to the study of social behaviour in both humans and animals, suggesting that social behavior in animals and humans is shaped primarily by genes and genetic evolution.

Bouchard, T. J., Lykken, D. T., McGue, M., & Segal, N. L. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250(4978), 223–228.

Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A. & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854.

Koenigshofer, K. A. & Nachman, M. (1974).  Selective Breeding for Taste Aversion Learning in Rats.  Paper presented at the 54th Annual Convention of the Western Psychological Association.  April 28, 1974.  San Francisco.

McGue, M., & Lykken, D. T. (1992). Genetic influence on risk of divorce. Psychological Science, 3(6), 368–373.

Plomin, R., Corley, R., DeFries, J. C., & Fulker, D. W. (1990). Individual differences in television viewing in early childhood: Nature as well as nurture. Psychological Science, 1(6), 371–377.

Plomin, R., DeFries, J. C., Knopik, V. S., & Neiderhiser, J. M. (2012). Behavioral genetics. New York, NY: Worth Publishers.

Scott, J. P., & Fuller, J. L. (1998). Genetics and the social behavior of the dog. Chicago, IL: University of Chicago Press.

Turkheimer, E. (2000). Three laws of behavior genetics and what they mean. Current Directions in Psychological Science, 9(5), 160–164.

Wilson, E. O. (1975).   Sociobiology: The New Synthesis . Cambridge, MA: Belknap Press.

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The Nature-Nurture Question by Eric Turkheimer is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License .

Sociobiology adapted by Kenneth A. Koenigshofer, Ph.D., Chaffey College, from Sociobiology. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/sociobiology . License: CC BY-SA: Attribution-ShareAlike

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Brain development and the nature versus nurture debate

Affiliation.

• 1 Department of Cognitive Science, University of California, San Diego, La Jolla, CA, USA. [email protected]
• PMID: 21489380
• DOI: 10.1016/B978-0-444-53884-0.00015-4

Over the past three decades, developmental neurobiologists have made tremendous progress in defining basic principles of brain development. This work has changed the way we think about how brains develop. Thirty years ago, the dominant model was strongly deterministic. The relationship between brain and behavioral development was viewed as unidirectional; that is, brain maturation enables behavioral development. The advent of modern neurobiological methods has provided overwhelming evidence that it is the interaction of genetic factors and the experience of the individual that guides and supports brain development. Brains do not develop normally in the absence of critical genetic signaling, and they do not develop normally in the absence of essential environmental input. The fundamental facts about brain development should be of critical importance to neuropsychologists trying to understand the relationship between brain and behavioral development. However, the underlying assumptions of most contemporary psychological models reflect largely outdated ideas about how the biological system develops and what it means for something to be innate. Thus, contemporary models of brain development challenge the foundational constructs of the nature versus nurture formulation in psychology. The key to understanding the origins and emergence of both the brain and behavior lies in understanding how inherited and environmental factors are engaged in the dynamic and interactive processes that define and guide development of the neurobehavioral system.

Copyright © 2011 Elsevier B.V. All rights reserved.

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• Research Support, N.I.H., Extramural
• Behavior / physiology*
• Body Patterning
• Brain / embryology*
• Brain / growth & development*
• Brain / physiology
• Environment*
• Inheritance Patterns
• Neural Stem Cells / physiology
• Neuronal Plasticity
• Signal Transduction

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• 1 R01 HD060595/HD/NICHD NIH HHS/United States
• R01-HD25077/HD/NICHD NIH HHS/United States

Encyclopedia of Personality and Individual Differences pp 1–5 Cite as

Nature-Nurture Debate

• Christian Montag 3 , 4 &
• Elisabeth Hahn 5  
• Living reference work entry
• First Online: 02 February 2018

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Epigenome , Gene by environment , Intelligence , Molecular genetics , Nature , Nurture , Personality

Introduction

Among the earliest testimonials of human civilization is a deep intuition that some aspects of human behavior originate in our genetic makeup, while others feel like the result of upbringing or exercise. A central question posed by both ancient philosophers such as Aristotle and modern researchers in the twenty-first century deals with the impact of nature and nurture on human characteristics such as personality or intelligence. While Aristotle questioned how resemblances between parents and their offspring can be explained (Henry 2006 ), Sir Francis Galton ( 1869 ) as one of the first scientists already dealt in his famous work Hereditary Genius with the genetics of intelligence.

The nature versus nurture debate represents one of the oldest issues in the research of human behavior dealing with the question whether inherited traits or life experiences (e.g., upbringing)...

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Arslan, R. C., & Penke, L. (2015). Zeroing in on the genetics of intelligence. Journal of Intelligence, 3 (2), 41–45.

Article   Google Scholar  

Bakermans-Kranenburg, M. J., Van IJzendoorn, M. H., Pijlman, F. T., Mesman, J., & Juffer, F. (2008). Experimental evidence for differential susceptibility: Dopamine D4 receptor polymorphism (DRD4 VNTR) moderates intervention effects on toddlers’ externalizing behavior in a randomized controlled trial. Developmental Psychology, 44 (1), 293–300.

Article   PubMed   Google Scholar  

Caspi, A., Sugden, K., Moffitt, T. E., Taylor, A., Craig, I. W., Harrington, H., et al. (2003). Influence of life stress on depression: Moderation by a polymorphism in the 5-HTT gene. Science, 301 (5631), 386–389.

Galton, F. (1876). The history of twins, as a criterion of the relative powers of nature and nurture. The Journal of the Anthropological Institute of Great Britain and Ireland, 5 , 391–406.

Galton, F. (1869). Hereditary genius: An inquiry into its laws and consequences . New York: Macmillan.

Book   Google Scholar  

Gillham, N. W. (2001). Sir Francis Galton and the birth of eugenics. Annual review of genetics, 35 (1), 83–101.

Haas, B. W., Filkowski, M. M., Cochran, R. N., Denison, L., Ishak, A., Nishitani, S., & Smith, A. K. (2016). Epigenetic modification of OXT and human sociability. Proceedings of the National Academy of Sciences, 113 (27), E3816–E3823.

Hahn, E., & Spinath, F. M. (2017). Quantitative behavior genetics of internet addiction. In Internet addiction (pp. 125–140). Cham: Springer International Publishing.

Chapter   Google Scholar  

Henry, D. (2006). Aristotle on the mechanism of inheritance. Journal of the History of Biology, 39 (3), 425–455.

Jang, K. L., Livesley, W. J., & Vemon, P. A. (1996). Heritability of the big five personality dimensions and their facets: A twin study. Journal of Personality, 64 (3), 577–592.

Karg, K., Burmeister, M., Shedden, K., & Sen, S. (2011). The serotonin transporter promoter variant (5-HTTLPR), stress, and depression meta-analysis revisited: Evidence of genetic moderation. Archives of General Psychiatry, 68 (5), 444–454.

Article   PubMed   PubMed Central   Google Scholar  

Knopik, V. S., Neiderhiser, J. M., DeFries, J. C., & Plomin, R. (2016). Behavioral genetics . New York: Worth.

Google Scholar  

Langbehn, D. R., Brinkman, R. R., Falush, D., Paulsen, J. S., & Hayden, M. R. (2004). A new model for prediction of the age of onset and penetrance for Huntington’s disease based on CAG length. Clinical Genetics, 65 (4), 267–277.

Meaney, M. J. (2001). Nature, nurture, and the disunity of knowledge. Annals of the New York Academy of Sciences, 935 (1), 50–61.

Meaney, M. J. (2010). Epigenetics and the biological definition of gene × environment interactions. Child Development, 81 (1), 41–79.

Mitchell, C., Notterman, D., Brooks-Gunn, J., Hobcraft, J., Garfinkel, I., Jaeger, K., et al. (2011). Role of mother’s genes and environment in postpartum depression. Proceedings of the National Academy of Sciences, 108 (20), 8189–8193.

Montag, C., & Reuter, M. (2014). Disentangling the molecular genetic basis of personality: From monoamines to neuropeptides. Neuroscience & Biobehavioral Reviews, 43 , 228–239.

Montag, C., Jurkiewicz, M., & Reuter, M. (2012). The role of the catechol-O-methyltransferase (COMT) gene in personality and related psychopathological disorders. CNS & Neurological Disorders-Drug Targets (Formerly Current Drug Targets-CNS & Neurological Disorders), 11 (3), 236–250.

Montag, C., Hall, J., Plieger, T., Felten, A., Markett, S., Melchers, M., & Reuter, M. (2015). The DRD3 Ser9Gly polymorphism, Machiavellianism, and its link to schizotypal personality. Journal of Neuroscience, Psychology, & Economics, 8 (1), 48–57.

Montag, C., Hahn, E., Reuter, M., Spinath, F. M., Davis, K., & Panksepp, J. (2016). The role of nature and nurture for individual differences in primary emotional systems: Evidence from a twin study. PloS One, 11 (3), e0151405.

Plieger, T., Felten, A., Melchers, M., Markett, S., Montag, C., & Reuter, M. (2018). Association between a functional polymorphism on the dopamine-β-hydroxylase gene and reward dependence in two independent samples. Personality and Individual Differences,121 , 218–222.

Polderman, T. J., Benyamin, B., De Leeuw, C. A., Sullivan, P. F., Van Bochoven, A., Visscher, P. M., & Posthuma, D. (2015). Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nature Genetics, 47 (7), 702–709.

Purcell, S. (2002). Variance components models for gene–environment interaction in twin analysis. Twin Research and Human Genetics, 5 (6), 554–571.

Reiss, D., Leve, L. D., & Neiderhiser, J. M. (2013). How genes and the social environment moderate each other. American Journal of Public Health, 103 (S1), S111–S121.

Riemann, R., Angleitner, A., & Strelau, J. (1997). Genetic and environmental influences on personality: A study of twins reared together using the self-and peer report NEO-FFI scales. Journal of Personality, 65 (3), 449–475.

Risch, N., Herrell, R., Lehner, T., Liang, K. Y., Eaves, L., Hoh, J., et al. (2009). Interaction between the serotonin transporter gene (5-HTTLPR), stressful life events, and risk of depression: A meta-analysis. Jama, 301 (23), 2462–2471.

Toyokawa, S., Uddin, M., Koenen, K. C., & Galea, S. (2012). How does the social environment ‘get into the mind’? Epigenetics at the intersection of social and psychiatric epidemiology. Social Science & Medicine, 74 (1), 67–74.

VanTassel-Baska, J. (2005). Gifted programs and services: What are the nonnegotiables? Theory Into Practice, 44 (2), 90–97.

Youngson, N. A., & Whitelaw, E. (2008). Transgenerational epigenetic effects. Annual Review of Genomics and Human Genetics, 9 , 233–257.

Zhang, T. Y., & Meaney, M. J. (2010). Epigenetics and the environmental regulation of the genome and its function. Annual Review of Psychology, 61 , 439–466.

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Acknowledgment

The position of Christian Montag is funded by a Heisenberg grant awarded to him by the German Research Foundation (DFG, MO2363/3-2).

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Christian Montag

Key Laboratory for NeuroInformation/Center for Information in Medicine, School of Life Science and Technology, University of Electronic Science and Technology of China, Chengdu, China

Department of Psychology, Saarland University, Saarbrücken, Germany

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Montag, C., Hahn, E. (2018). Nature-Nurture Debate. In: Zeigler-Hill, V., Shackelford, T. (eds) Encyclopedia of Personality and Individual Differences. Springer, Cham. https://doi.org/10.1007/978-3-319-28099-8_822-1

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7 The Nature-Nurture Question

People have a deep intuition about what has been called the “nature–nurture question.” Some aspects of our behavior feel as though they originate in our genetic makeup, while others feel like the result of our upbringing or our own hard work. The scientific field of behavior genetics attempts to study these differences empirically, either by examining similarities among family members with different degrees of genetic relatedness, or, more recently, by studying differences in the DNA of people with different behavioral traits. The scientific methods that have been developed are ingenious, but often inconclusive. Many of the difficulties encountered in the empirical science of behavior genetics turn out to be conceptual, and our intuitions about nature and nurture get more complicated the harder we think about them. In the end, it is an oversimplification to ask how “genetic” some particular behavior is. Genes and environments always combine to produce behavior, and the real science is in the discovery of how they combine for a given behavior.

Learning Objectives

• Understand what the nature–nurture debate is and why the problem fascinates us.
• Understand why nature–nurture questions are difficult to study empirically.
• Know the major research designs that can be used to study nature–nurture questions.
• Appreciate the complexities of nature–nurture and why questions that seem simple turn out not to have simple answers.

Introduction

There are three related problems at the intersection of philosophy and science that are fundamental to our understanding of our relationship to the natural world: the mind–body problem, the free will problem, and the nature–nurture problem. These great questions have a lot in common. Everyone, even those without much knowledge of science or philosophy, has opinions about the answers to these questions that come simply from observing the world we live in. Our feelings about our relationship with the physical and biological world often seem incomplete. We are in control of our actions in some ways, but at the mercy of our bodies in others; it feels obvious that our consciousness is some kind of creation of our physical brains, at the same time we sense that our awareness must go beyond just the physical. This incomplete knowledge of our relationship with nature leaves us fascinated and a little obsessed, like a cat that climbs into a paper bag and then out again, over and over, mystified every time by a relationship between inner and outer that it can see but can’t quite understand.

It may seem obvious that we are born with certain characteristics while others are acquired, and yet of the three great questions about humans’ relationship with the natural world, only nature–nurture gets referred to as a “debate.” In the history of psychology, no other question has caused so much controversy and offense: We are so concerned with nature–nurture because our very sense of moral character seems to depend on it. While we may admire the athletic skills of a great basketball player, we think of his height as simply a gift, a payoff in the “genetic lottery.” For the same reason, no one blames a short person for his height or someone’s congenital disability on poor decisions: To state the obvious, it’s “not their fault.” But we do praise the concert violinist (and perhaps her parents and teachers as well) for her dedication, just as we condemn cheaters, slackers, and bullies for their bad behavior.

The problem is, most human characteristics aren’t usually as clear-cut as height or instrument-mastery, affirming our nature–nurture expectations strongly one way or the other. In fact, even the great violinist might have some inborn qualities—perfect pitch, or long, nimble fingers—that support and reward her hard work. And the basketball player might have eaten a diet while growing up that promoted his genetic tendency for being tall. When we think about our own qualities, they seem under our control in some respects, yet beyond our control in others. And often the traits that don’t seem to have an obvious cause are the ones that concern us the most and are far more personally significant. What about how much we drink or worry? What about our honesty, or religiosity, or sexual orientation? They all come from that uncertain zone, neither fixed by nature nor totally under our own control.

One major problem with answering nature-nurture questions about people is, how do you set up an experiment? In nonhuman animals, there are relatively straightforward experiments for tackling nature–nurture questions. Say, for example, you are interested in aggressiveness in dogs. You want to test for the more important determinant of aggression: being born to aggressive dogs or being raised by them. You could mate two aggressive dogs—angry Chihuahuas—together, and mate two nonaggressive dogs—happy beagles—together, then switch half the puppies from each litter between the different sets of parents to raise. You would then have puppies born to aggressive parents (the Chihuahuas) but being raised by nonaggressive parents (the Beagles), and vice versa, in litters that mirror each other in puppy distribution. The big questions are: Would the Chihuahua parents raise aggressive beagle puppies? Would the beagle parents raise  non aggressive Chihuahua puppies? Would the puppies’  nature  win out, regardless of who raised them? Or… would the result be a combination of nature  and  nurture? Much of the most significant nature–nurture research has been done in this way (Scott & Fuller, 1998), and animal breeders have been doing it successfully for thousands of years. In fact, it is fairly easy to breed animals for behavioral traits.

With people, however, we can’t assign babies to parents at random, or select parents with certain behavioral characteristics to mate, merely in the interest of science (though history does include horrific examples of such practices, in misguided attempts at “eugenics,” the shaping of human characteristics through intentional breeding). In typical human families, children’s biological parents raise them, so it is very difficult to know whether children act like their parents due to genetic (nature) or environmental (nurture) reasons. Nevertheless, despite our restrictions on setting up human-based experiments, we do see real-world examples of nature-nurture at work in the human sphere—though they only provide partial answers to our many questions.

The science of how genes and environments work together to influence behavior is called  behavioral genetics . The easiest opportunity we have to observe this is the  adoption study . When children are put up for adoption, the parents who give birth to them are no longer the parents who raise them. This setup isn’t quite the same as the experiments with dogs (children aren’t assigned to random adoptive parents in order to suit the particular interests of a scientist) but adoption still tells us some interesting things, or at least confirms some basic expectations. For instance, if the biological child of tall parents were adopted into a family of short people, do you suppose the child’s growth would be affected? What about the biological child of a Spanish-speaking family adopted at birth into an English-speaking family? What language would you expect the child to speak? And what might these outcomes tell you about the difference between height and language in terms of nature-nurture?

Another option for observing nature-nurture in humans involves  twin studies . There are two types of twins: monozygotic (MZ) and dizygotic (DZ). Monozygotic twins, also called “identical” twins, result from a single zygote (fertilized egg) and have the same DNA. They are essentially clones. Dizygotic twins, also known as “fraternal” twins, develop from two zygotes and share 50% of their DNA. Fraternal twins are ordinary siblings who happen to have been born at the same time. To analyze nature–nurture using twins, we compare the similarity of MZ and DZ pairs. Sticking with the features of height and spoken language, let’s take a look at how nature and nurture apply: Identical twins, unsurprisingly, are almost perfectly similar for height. The heights of fraternal twins, however, are like any other sibling pairs: more similar to each other than to people from other families, but hardly identical. This contrast between twin types gives us a clue about the role genetics plays in determining height. Now consider spoken language. If one identical twin speaks Spanish at home, the co-twin with whom she is raised almost certainly does too. But the same would be true for a pair of fraternal twins raised together. In terms of spoken language, fraternal twins are just as similar as identical twins, so it appears that the genetic match of identical twins doesn’t make much difference.

Twin and adoption studies are two instances of a much broader class of methods for observing nature-nurture called quantitative genetics, the scientific discipline in which similarities among individuals are analyzed based on how biologically related they are. We can do these studies with siblings and half-siblings, cousins, twins who have been separated at birth and raised separately (Bouchard, Lykken, McGue, & Segal, 1990; such twins are very rare and play a smaller role than is commonly believed in the science of nature–nurture), or with entire extended families (see Plomin, DeFries, Knopik, & Neiderhiser, 2012, for a complete introduction to research methods relevant to nature–nurture).

For better or for worse, contentions about nature–nurture have intensified because quantitative genetics produces a number called a  heritability coefficient , varying from 0 to 1, that is meant to provide a single measure of genetics’ influence of a trait. In a general way, a heritability coefficient measures how strongly differences among individuals are related to differences among their genes. But beware: Heritability coefficients, although simple to compute, are deceptively difficult to interpret. Nevertheless, numbers that provide simple answers to complicated questions tend to have a strong influence on the human imagination, and a great deal of time has been spent discussing whether the heritability of intelligence or personality or depression is equal to one number or another.

One reason nature–nurture continues to fascinate us so much is that we live in an era of great scientific discovery in genetics, comparable to the times of Copernicus, Galileo, and Newton, with regard to astronomy and physics. Every day, it seems, new discoveries are made, new possibilities proposed. When Francis Galton first started thinking about nature–nurture in the late-19th century he was very influenced by his cousin, Charles Darwin, but genetics  per se  was unknown. Mendel’s famous work with peas, conducted at about the same time, went undiscovered for 20 years; quantitative genetics was developed in the 1920s; DNA was discovered by Watson and Crick in the 1950s; the human genome was completely sequenced at the turn of the 21st century; and we are now on the verge of being able to obtain the specific DNA sequence of anyone at a relatively low cost. No one knows what this new genetic knowledge will mean for the study of nature–nurture, but as we will see in the next section, answers to nature–nurture questions have turned out to be far more difficult and mysterious than anyone imagined.

What Have We Learned About Nature–Nurture?

It would be satisfying to be able to say that nature–nurture studies have given us conclusive and complete evidence about where traits come from, with some traits clearly resulting from genetics and others almost entirely from environmental factors, such as childrearing practices and personal will; but that is not the case. Instead,  everything  has turned out to have some footing in genetics. The more genetically-related people are, the more similar they are—for  everything : height, weight, intelligence, personality, mental illness, etc. Sure, it seems like common sense that some traits have a genetic bias. For example, adopted children resemble their biological parents even if they have never met them, and identical twins are more similar to each other than are fraternal twins. And while certain psychological traits, such as personality or mental illness (e.g., schizophrenia), seem reasonably influenced by genetics, it turns out that the same is true for political attitudes, how much television people watch (Plomin, Corley, DeFries, & Fulker, 1990), and whether or not they get divorced (McGue & Lykken, 1992).

It may seem surprising, but genetic influence on behavior is a relatively recent discovery. In the middle of the 20th century, psychology was dominated by the doctrine of behaviorism, which held that behavior could only be explained in terms of environmental factors. Psychiatry concentrated on psychoanalysis, which probed for roots of behavior in individuals’ early life-histories. The truth is, neither behaviorism nor psychoanalysis is incompatible with genetic influences on behavior, and neither Freud nor Skinner was naive about the importance of organic processes in behavior. Nevertheless, in their day it was widely thought that children’s personalities were shaped entirely by imitating their parents’ behavior, and that schizophrenia was caused by certain kinds of “pathological mothering.” Whatever the outcome of our broader discussion of nature–nurture, the basic fact that the best predictors of an adopted child’s personality or mental health are found in the biological parents he or she has never met, rather than in the adoptive parents who raised him or her, presents a significant challenge to purely environmental explanations of personality or psychopathology. The message is clear: You can’t leave genes out of the equation. But keep in mind, no behavioral traits are completely inherited, so you can’t leave the environment out altogether, either.

Trying to untangle the various ways nature-nurture influences human behavior can be messy, and often common-sense notions can get in the way of good science. One very significant contribution of behavioral genetics that has changed psychology for good can be very helpful to keep in mind: When your subjects are biologically-related, no matter how clearly a situation may seem to point to environmental influence, it is never safe to interpret a behavior as wholly the result of nurture without further evidence. For example, when presented with data showing that children whose mothers read to them often are likely to have better reading scores in third grade, it is tempting to conclude that reading to your kids out loud is important to success in school; this may well be true, but the study as described is inconclusive, because there are genetic  as well as  environmental pathways between the parenting practices of mothers and the abilities of their children. This is a case where “correlation does not imply causation,” as they say. To establish that reading aloud causes success, a scientist can either study the problem in adoptive families (in which the genetic pathway is absent) or by finding a way to randomly assign children to oral reading conditions.

The outcomes of nature–nurture studies have fallen short of our expectations (of establishing clear-cut bases for traits) in many ways. The most disappointing outcome has been the inability to organize traits from  more – to  less -genetic. As noted earlier, everything has turned out to be at least  somewhat  heritable (passed down), yet nothing has turned out to be  absolutely  heritable, and there hasn’t been much consistency as to which traits are  more  heritable and which are  less  heritable once other considerations (such as how accurately the trait can be measured) are taken into account (Turkheimer, 2000). The problem is conceptual: The heritability coefficient, and, in fact, the whole quantitative structure that underlies it, does not match up with our nature–nurture intuitions. We want to know how “important” the roles of genes and environment are to the development of a trait, but in focusing on “important” maybe we’re emphasizing the wrong thing. First of all, genes and environment are both crucial to  every  trait; without genes the environment would have nothing to work on, and too, genes cannot develop in a vacuum. Even more important, because nature–nurture questions look at the differences among people, the cause of a given trait depends not only on the trait itself, but also on the differences in that trait between members of the group being studied.

The classic example of the heritability coefficient defying intuition is the trait of having two arms. No one would argue against the development of arms being a biological, genetic process. But fraternal twins are just as similar for “two-armedness” as identical twins, resulting in a heritability coefficient of zero for the trait of having two arms. Normally, according to the heritability model, this result (coefficient of zero) would suggest all nurture, no nature, but we know that’s not the case. The reason this result is not a tip-off that arm development is less genetic than we imagine is because people  do not vary  in the genes related to arm development—which essentially upends the heritability formula. In fact, in this instance, the opposite is likely true: the extent that people differ in arm number is likely the result of accidents and, therefore, environmental. For reasons like these, we always have to be very careful when asking nature–nurture questions, especially when we try to express the answer in terms of a single number. The heritability of a trait is not simply a property of that trait, but a property of the trait in a particular context of relevant genes and environmental factors.

Another issue with the heritability coefficient is that it divides traits’ determinants into two portions—genes and environment—which are then calculated together for the total variability. This is a little like asking how much of the experience of a symphony comes from the horns and how much from the strings; the ways instruments or genes integrate is more complex than that. It turns out to be the case that, for many traits, genetic differences affect behavior under some environmental circumstances but not others—a phenomenon called gene-environment interaction , or G x E. In one well-known example, Caspi et al. (2002) showed that among maltreated children, those who carried a particular allele of the MAOA gene showed a predisposition to violence and antisocial behavior, while those with other alleles did not. Whereas, in children who had not been maltreated, the gene had no effect. Making matters even more complicated are very recent studies of what is known as epigenetics, a process in which the DNA itself is modified by environmental events, and those genetic changes transmitted to children.

The video above explains basics of epigenetics, and shares the story of two “clones” or persons that were born identical, but had very different life circumstances. One person was stressed and ate poorly, the other had an easier life and ate healthy ways. If you and your clone person were examined at age 50, you would look quite different. The one who had eaten poorly would probably look more tired. If scientists looked at your DNA however, your DNA would be still the same, or your genomes would be the same. However you would have different epigenomes – meaning that some markers on your genes would look differently. If you think of DNA and genes as a paragraph, then epigenomes could be the punctuation of the paragraph. As you know, punctuation changes the meaning and expression of a paragraph. The epigenome is the “marching orders” for what the gene is supposed to do, and can be affected by environmental experiences. What we do, what we eat, what we smoke, who we hang out with, all of these affect our epigenomes or the expression of our genes.

One of the most educational findings (and historically tragic events) on the impact of adverse environmental conditions (phenotype experiences)  and physical health (genotype experiences) comes from studies of the children of women who were pregnant during two civilian famines of World War II: the Siege of Leningrad (1941–44) (Bateson, 2001) and the Dutch Hunger Winter (1944–1945) (Stanner et al., 1997). In the Netherlands famine, women who were previously well nourished were subjected to low caloric intake and associated environmental stressors. Women who endured the famine in the late stages of pregnancy gave birth to smaller babies (Lumey & Stein, 1997) and these children had an increased risk of insulin resistance later in life (Painter, Roseboom, & Bleker, 2005). In addition, offspring who were starved prenatally later experienced impaired glucose tolerance in adulthood, even when food was more abundant (Stanner et al., 1997). Famine exposure at various stages of gestation was associated with a wide range of risks such as increased obesity, higher rates of coronary heart disease, and lower birth weight (Lumey & Stein, 1997). Interestingly, when examined 60 years later, people exposed to famine prenatally showed reduced DNA methylation compared with their unexposed same-sex siblings (Heijmans et al., 2008).

Parental investment and programming of stress responses in the offspring

The most comprehensive study to date of variations in parental investment and epigenetic inheritance in mammals is that of the maternally transmitted responses to stress in rats. In rat pups, maternal nurturing (licking and grooming) during the first week of life is associated with long-term programming of individual differences in stress responsiveness, emotionality, cognitive performance, and reproductive behavior (Caldji et al., 1998; Francis, Diorio, Liu, & Meaney, 1999; Liu et al., 1997; Myers, Brunelli, Shair, Squire, & Hofer, 1989; Stern, 1997). In adulthood, the offspring of mothers that exhibit increased levels of pup licking and grooming over the first week of life show increased expression of the glucocorticoid receptor in the hippocampus (a brain structure associated with stress responsivity as well as learning and memory) and a lower hormonal response to stress compared with adult animals reared by low licking and grooming mothers (Francis et al., 1999; Liu et al., 1997). Moreover, rat pups that received low levels of maternal licking and grooming during the first week of life showed decreased histone acetylation and increased DNA methylation of a neuron-specific promoter of the glucocorticoid receptor gene (Weaver et al., 2004). The expression of this gene is then reduced, the number of glucocorticoid receptors in the brain is decreased, and the animals show a higher hormonal response to stress throughout their life. The effects of maternal care on stress hormone responses and behaviour in the offspring can be eliminated in adulthood by pharmacological treatment (HDAC inhibitor trichostatin A, TSA) or dietary amino acid supplementation (methyl donor L-methionine), treatments that influence histone acetylation, DNA methylation, and expression of the glucocorticoid receptor gene (Weaver et al., 2004; Weaver et al., 2005). This series of experiments shows that histone acetylation and DNA methylation of the glucocorticoid receptor gene promoter is a necessary link in the process leading to the long-term physiological and behavioral sequelae of poor maternal care. This points to a possible molecular target for treatments that may reverse or ameliorate the traces of childhood maltreatment.

Several studies have attempted to determine to what extent the findings from model animals are transferable to humans. Examination of post-mortem brain tissue from healthy human subjects found that the human equivalent of the glucocorticoid receptor gene promoter (NR3C1 exon 1F promoter) is also unique to the individual (Turner, Pelascini, Macedo, & Muller, 2008). A similar study examining newborns showed that methylation of the glucocorticoid receptor gene promoter maybe an early epigenetic marker of maternal mood and risk of increased hormonal responses to stress in infants 3 months of age (Oberlander et al., 2008). Although further studies are required to examine the functional consequence of this DNA methylation, these findings are consistent with our studies in the neonate and adult offspring of low licking and grooming mothers that show increased DNA methylation of the promoter of the glucocorticoid receptor gene, decreased glucocorticoid receptor gene expression, and increased hormonal responses to stress (Weaver et al., 2004). Examination of brain tissue from suicide victims found that the human glucocorticoid receptor gene promoter is also more methylated in the brains of individuals who had experienced maltreatment during childhood (McGowan et al., 2009). These finding suggests that DNA methylation mediates the effects of early environment in both rodents and humans and points to the possibility of new therapeutic approaches stemming from translational epigenetic research. Indeed, similar processes at comparable epigenetic labile regions could explain why the adult offspring of high and low licking/grooming mothers exhibit widespread differences in hippocampal gene expression and cognitive function (Weaver, Meaney, & Szyf, 2006).

However, this type of research is limited by the inaccessibility of human brain samples. The translational potential of this finding would be greatly enhanced if the relevant epigenetic modification can be measured in an accessible tissue. Examination of blood samples from adult patients with bipolar disorder, who also retrospectively reported on their experiences of childhood abuse and neglect, found that the degree of DNA methylation of the human glucocorticoid receptor gene promoter was strongly positively related to the reported experience of childhood maltreatment decades earlier. For a relationship between a molecular measure and reported historical exposure, the effects size is extraordinarily large. This opens a range of new possibilities: given the large effect size and consistency of this association, measurement of the GR promoter methylation may effectively become a blood test measuring the physiological traces left on the genome by early experiences. Although this blood test cannot replace current methods of diagnosis, this unique and addition information adds to our knowledge of how disease may arise and be manifested throughout life. Near-future research will examine whether this measure adds value over and above simple reporting of early adversities when it comes to predicting important outcomes, such as response to treatment or suicide.

Epigenetic strategy to understanding gene-environment interactions

Some common questions about nature–nurture are, how susceptible is a trait to change, how malleable is it, and do we “have a choice” about it? These questions are much more complex than they may seem at first glance. For example, phenylketonuria is an inborn error of metabolism caused by a single gene; it prevents the body from metabolizing phenylalanine. Untreated, it causes mental retardation and death. But it can be treated effectively by a straightforward environmental intervention: avoiding foods containing phenylalanine. Height seems like a trait firmly rooted in our nature and unchangeable, but the average height of many populations in Asia and Europe has increased significantly in the past 100 years, due to changes in diet and the alleviation of poverty. Even the most modern genetics has not provided definitive answers to nature–nurture questions. When it was first becoming possible to measure the DNA sequences of individual people, it was widely thought that we would quickly progress to finding the specific genes that account for behavioral characteristics, but that hasn’t happened. There are a few rare genes that have been found to have significant (almost always negative) effects, such as the single gene that causes Huntington’s disease, or the Apolipoprotein gene that causes early onset dementia in a small percentage of Alzheimer’s cases. Aside from these rare genes of great effect, however, the genetic impact on behavior is broken up over many genes, each with very small effects. For most behavioral traits, the effects are so small and distributed across so many genes that we have not been able to catalog them in a meaningful way. In fact, the same is true of environmental effects. We know that extreme environmental hardship causes catastrophic effects for many behavioral outcomes, but fortunately extreme environmental hardship is very rare. Within the normal range of environmental events, those responsible for differences (e.g., why some children in a suburban third-grade classroom perform better than others) are much more difficult to grasp.

The difficulties with finding clear-cut solutions to nature–nurture problems bring us back to the other great questions about our relationship with the natural world: the mind-body problem and free will. Investigations into what we mean when we say we are aware of something reveal that consciousness is not simply the product of a particular area of the brain, nor does choice turn out to be an orderly activity that we can apply to some behaviors but not others. So it is with nature and nurture: What at first may seem to be a straightforward matter, able to be indexed with a single number, becomes more and more complicated the closer we look. The many questions we can ask about the intersection among genes, environments, and human traits—how sensitive are traits to environmental change, and how common are those influential environments; are parents or culture more relevant; how sensitive are traits to differences in genes, and how much do the relevant genes vary in a particular population; does the trait involve a single gene or a great many genes; is the trait more easily described in genetic or more-complex behavioral terms?—may have different answers, and the answer to one tells us little about the answers to the others.

It is tempting to predict that the more we understand the wide-ranging effects of genetic differences on all human characteristics—especially behavioral ones—our cultural, ethical, legal, and personal ways of thinking about ourselves will have to undergo profound changes in response. Perhaps criminal proceedings will consider genetic background. Parents, presented with the genetic sequence of their children, will be faced with difficult decisions about reproduction. These hopes or fears are often exaggerated. In some ways, our thinking may need to change—for example, when we consider the meaning behind the fundamental American principle that all men are created equal. Human beings differ, and like all evolved organisms they differ genetically. The Declaration of Independence predates Darwin and Mendel, but it is hard to imagine that Jefferson—whose genius encompassed botany as well as moral philosophy—would have been alarmed to learn about the genetic diversity of organisms. One of the most important things modern genetics has taught us is that almost all human behavior is too complex to be nailed down, even from the most complete genetic information, unless we’re looking at identical twins. The science of nature and nurture has demonstrated that genetic differences among people are vital to human moral equality, freedom, and self-determination, not opposed to them. As Mordecai Kaplan said about the role of the past in Jewish theology, genetics gets a vote, not a veto, in the determination of human behavior. We should indulge our fascination with nature–nurture while resisting the temptation to oversimplify it.

Epigenetics  is the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself.  Epigenetics looks at all events that occur in the absence of changes in DNA sequence. Epigenetics is looking at changes of the gene expression, rather than changes in the DNA code itself.

Epigenome: epigenome refers to the genetic patterns and information made up of chemical compounds and proteins that can attach to DNA, and direct such actions as turning genes on or off, controlling the production of proteins in particular cells and changing the expression of a gene. These changes in the epigenome may be passed down through heritance, or may be changed by environmental experiences.

Genotype: is an organism’s full hereditary information. … The genes that contribute to a trait”. Genotype is an organism’s full hereditary information.

Phenotype: is an organism’s actual observed properties, such as morphology, development, or behavior.

• Bouchard, T. J., Lykken, D. T., McGue, M., & Segal, N. L. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250(4978), 223–228.
• Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A. & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854.
• McGue, M., & Lykken, D. T. (1992). Genetic influence on risk of divorce. Psychological Science, 3(6), 368–373.
• Plomin, R., Corley, R., DeFries, J. C., & Fulker, D. W. (1990). Individual differences in television viewing in early childhood: Nature as well as nurture. Psychological Science, 1(6), 371–377.
• Plomin, R., DeFries, J. C., Knopik, V. S., & Neiderhiser, J. M. (2012). Behavioral genetics. New York, NY: Worth Publishers.
• Scott, J. P., & Fuller, J. L. (1998). Genetics and the social behavior of the dog. Chicago, IL: University of Chicago Press.
• Turkheimer, E. (2000). Three laws of behavior genetics and what they mean. Current Directions in Psychological Science, 9(5), 160–164.

This is an edited and adapted chapter from a chapter by Eric Turkheimer PhD, contributed to the NOBA project. The original authors bear no responsibility for this chapter. The original chapter can be found here:

Turkheimer, E. (2019). The nature-nurture question. In R. Biswas-Diener & E. Diener (Eds),  Noba textbook series: Psychology.  Champaign, IL: DEF publishers. Retrieved from  http://noba.to/tvz92edh

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• Published: 08 January 2021

Nurture might be nature: cautionary tales and proposed solutions

• Sara A. Hart   ORCID: orcid.org/0000-0001-9793-0420 1 , 2 ,
• Callie Little 2 , 3 &
• Elsje van Bergen   ORCID: orcid.org/0000-0002-5860-5745 4  

npj Science of Learning volume  6 , Article number:  2 ( 2021 ) Cite this article

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Across a wide range of studies, researchers often conclude that the home environment and children’s outcomes are causally linked. In contrast, behavioral genetic studies show that parents influence their children by providing them with both environment and genes, meaning the environment that parents provide should not be considered in the absence of genetic influences, because that can lead to erroneous conclusions on causation. This article seeks to provide behavioral scientists with a synopsis of numerous methods to estimate the direct effect of the environment, controlling for the potential of genetic confounding. Ideally, using genetically sensitive designs can fully disentangle this genetic confound, but these require specialized samples. In the near future, researchers will likely have access to measured DNA variants (summarized in a polygenic scores), which could serve as a partial genetic control, but that is currently not an option that is ideal or widely available. We also propose a work around for when genetically sensitive data are not readily available: the Familial Control Method. In this method, one measures the same trait in the parents as the child, and the parents’ trait is then used as a covariate (e.g., a genetic proxy). When these options are all not possible, we plead with our colleagues to clearly mention genetic confound as a limitation, and to be cautious with any environmental causal statements which could lead to unnecessary parent blaming.

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Most parents spend hours fretting over decisions about the environment they provide to their children. The scientific literature mirrors this idea. Across a wide range of studies from many psychological domains, researchers often conclude that the environment parents provide and children’s outcomes are causally linked, through environmental transmission (see Box 1 ). For example, a study examining the association of having a home library as an adolescent and later adult literacy, numeracy and technology skills drew our attention because of in-depth coverage in the Guardian ( https://www.theguardian.com/books/2018/oct/10/growing-up-in-a-house-full-of-books-is-major-boost-to-literacy-and-numeracy-study-finds ). This study used a very rich and well-powered dataset, and found a correlation between the number of books in adolescents’ homes and literacy performance in adulthood. They conclude that “growing up with home libraries boosts adult skills”, inferring a causal connection 1 . This is depicted in Fig. 1 . Here we discuss how the correlation between the environments parents provide, the “rearing environment”, and their children’s outcomes can indeed be fully due to a causal association, or importantly, can also be partly or fully due to a genetic confounding, illustrated in Fig. 2 (see Footnote 1 in the Supplementary Notes ). After highlighting the problem, we suggest ways that psychological scientists can examine research questions related to the rearing environment and children’s outcomes in ways that account for, or at least acknowledge, genetic confounding.

Number of books in the home is thought to be an environmental causal effect on children’s reading ability. Figure by ref. 66 available at https://bit.ly/3gl8MVk under a CC BY 4.0 license.

Parents share genes related to reading ability with their children, and also control the number of books in their home. This creates gene–environment interplay. It is important to note that the environmental effect may still have a causal role, even with gene–environment interplay. If genes play a role but are not modeled (as in Fig. 1 ), the correlation between the environmental measure and the child’s trait is genetically confounded. Here, the role of genes is modeled, allowing for an estimation of the genetic effect and the environmental effect. Figure by ref. 66 available at https://bit.ly/31c52z9 under a CC BY 4.0 license.

Genetic control of exposure to the environment

Decades of work from behavioral genetics show that children’s traits are influenced by both genetic and environmental effects 2 , 3 . Likely more surprising to hear for most is that genetic influences are often seen on measures of the “environment”, suggesting that the contexts surrounding children are partly under genetic control 4 . For example, a meta-analysis found cumulative support for genetic influences on the parenting children received 5 . This idea, that there is genetic influence on exposure to environments, is called a gene–environment correlation. A gene–environment correlation describes the process by which a person’s genotype influences their exposure to the environment 6 . It is certainly not the case that genes are doing this directly, but instead genotypes matter for aspects of our personality, behaviors and cognitions, which then influence how we interact with our environment and how others interact with us 7 . This concept of an individual purposely and dynamically interacting with their surrounding environment is not limited to behavioral genetics; similar processes have been described in other literatures, for example person-centered interactions 8 and the Selective Optimization with Compensation 9 .

Specifically, there are three types of gene–environment correlations that can result in genetic confounds 6 . First, a “passive gene–environment correlation” describes the association between the genotype a child inherits from their parents and the environment the child is raised in. Another way to think of it is that genes are a third variable which influence both the rearing environment a child receives as well as the child’s own traits, via genetic transmission from parents to child. This means it is not possible to draw causal conclusions between the rearing environment and children’s traits. For example, home environments have been found to be less chaotic for children with high effortful control, with results indicating that the same genes in parents which contribute to the levels of structure in their home (i.e., factors such as absence of noise and crowding, as well as presence of structure and routine) are also transmitted to their children and contribute to effortful control 10 . Second, an “evocative gene–environment correlation” is when a person’s genetically influenced trait elicits, or evokes, a specific response from others in the environment. For example, it has been found that a person’s genes are associated with being rated as “more likeable” by others, meaning how others perceive you as a social partner, and then likely interact with you, is influenced by your genes 11 . Third, an “active gene–environment correlation” describes the association of a person’s genetically influenced traits and the environments they select. For example, the genetically influenced personality trait of socialization, measured in childhood, was associated with exposure to risky environments related to substance abuse in adolescence, in that children with low socialization were exposed to more risky environments 12 . All three have the potential to cloud the true combination of genetic and environmental influences transmitted between parents and children (i.e., genetic confounding), but it is theorized that passive gene–environment correlations have a greater effect in childhood 13 , and as such passive gene–environment correlations are the focus of our review.

To give an example of how (passive) gene–environment correlations can result in genetic confounding in studies focused on the rearing environment, a high impact finding reported that parents with higher math anxiety have children with higher math anxiety, solely due to the home environment 14 . The authors attribute helping with math homework as the causal environmental factor, concluding that parents with high math anxiety should not help with their children’s math homework. This causal connection could exist, but equally parents with math anxiety also pass on genetic (and environmental) risks related to both lower math cognition and higher math anxiety 15 . Because this genetic transmission was not controlled for, causal claims and associated parenting advice are not justified.

Another example, this time from the medical literature, examined the intergenerational transmission of smoking behavior from parents to adolescents, concluding that “the attitudes, beliefs, and behaviors toward [adolescent] cigarette use are learned through [parent] modeling” 16 . Again, this study focused on the environmental transmission from parents to offspring without accounting for the transmission of genes related to smoking behaviors and risk-taking behaviors 17 . Furthermore, the authors conclude that smoking cessation interventions in adults can reduce smoking in subsequent generations. Parent-centered interventions might help to reduce adolescent smoking, but what is overlooked is that children carry their own genetic risks for smoking, and direct intervention with the adolescents 18 could more strongly influence their smoking behaviors.

We are certainly not the first to point out this familial transmission confound within the ecological literature. Indeed, nearly 40 years ago, Scarr and McCartney proposed that “the human experience and its effects on development depend primarily on the evolved nature of the human genome” 13 , and nearly 30 years ago Plomin and Bergeman 19 addressed the prevalence of genetic confounding by illustrating that genetic influences are found on most if not all environmental measures. Since then, several reviews have pointed to multiple examples from parental warmth to alcohol use to depression where causal pathways from parent behavior to child outcomes are reported, without accounting for genetic confounding 20 , 21 , 22 . These reviews have called for researchers to use caution with causal statements, and to address genetic confounding in their limitations. Further, they have asked for journal editors and reviewers to be better watch-dogs in this endeavor; to insist that manuscripts adhere to these standards. However, based on our experience listening to conference presentations and reading press releases and newspaper articles, we believe these guidelines are not yet being met.

We believe a reason why these previous reviews have not successfully changed minds and methods is because they have not given actionable correlational design solutions to researchers outside of behavior genetics. Therefore, when faced with not doing the work or publishing work with only a potential genetic confound, researchers have chosen the latter. Therefore, in the following section we will give many possible solutions, from genetically sensitive designs to design solutions that work in lieu of genetically sensitive data, and finally, a renewed call for changes in reporting standards.

Box 1 A glossary of some key terms

What researchers can do.

The designs that we discuss below present a not all-encompassing but global overview of genetically sensitive designs and polygenic-scores (PGS) designs, and include a genetic-proxy control design (the “Familial Control Method”), which we recommend when genetically sensitive data are not available, as well as several other proxy control designs. These designs vary in how well they disentangle the genetic confound and in how challenging they are in terms of obtaining and analyzing the data.

Genetically sensitive designs

Genetically sensitive designs are ideal for studying genetic and environmental influences and their interplay. These designs take advantage of samples of related individuals that differ in genetic relatedness (e.g., monozygotic and dizygotic twins; Fig. 3 ) or differ in environmental exposure (e.g., monozygotic twins reared apart). By far the most commonly used genetically sensitive design is the classical twin design. This design works because twins share either all (identical or monozygotic twins) or half (non-identical or dizygotic twins) of their genes 23 . Both types of twins share some parts of their environment such as their home, school, and neighborhood (referred to as common or shared environmental influences), and experience some aspects of their environments separately from each other such as peer groups, hobbies, or illness (referred to as unique or non-shared environmental influences). By comparing the average correlation between the two twins in a twin pair on a trait for monozygotic versus dizygotic twins, variance can be partitioned into additive genetic influences or heritability, shared environmental influences, and non-shared environmental influences (see Footnote 2 in the Supplementary Notes ) (Fig. 4 ). Heritability of a trait is indicated if the correlation between monozygotic twins is higher than that of dizygotic twins. Shared environmental influences are estimated by subtracting the heritability estimate from the monozygotic twin correlation, and the estimated shared environmental influences is larger when the correlation coefficient between monozygotic versus dizygotic twins are close in magnitude. Finally, non-shared environmental influences are estimated by subtracting the monozygotic twin correlation from one.

The scatter plots depict how much the two types of (reared-together) twins resemble their co-twin on reading ability. Each dot represents the reading scores of both children within a pair. It can be seen that monozygotic twins are much more alike. From this, it can be concluded that differences between children are largely due to genetic differences. The data come from van Bergen et al. 34 and represent word-reading fluency test scores in Grade 2 of twin pairs with complete data. The score is the number of words read correctly within 1 min. In this sample, the monozygotic and dizygotic twin correlations were 0.84 and 0.46, respectively, which yield estimates using the Falconer formulas 67 of A  = 0.76, C  = 0.08, and E  = 0.16 (see Fig. 4 ). Figure by ref. 66 available at https://bit.ly/3k4w2Ji under a CC BY 4.0 license.

In behavioral-genetic models, the three sources of influences on individual differences are commonly labeled by the letters A, C, and E, respectively, stemming from A dditive genetic influences (also known as heritability, and sometimes represented by an h 2 instead on an A), C ommon environmental influences (also known as shared environmental influences), and non-shared E nvironmental influences (and measurement E rror). Note that the latter are by definition uncorrelated between twins. See for a detailed representation of the classical twin model, for example, Figure A.9 in ref. 23 ; r MZ  = monozygotic twin correlation; r DZ  = dizygotic twin correlation. Figure by ref. 66 available at https://bit.ly/2Xkr29P under a CC BY 4.0 license.

With regard to disentangling possible genetic confounds and instead studying the direct effect of specific aspects of the rearing environment, classical twin studies are limited because both type of twins commonly share their rearing environments. For example, twin children growing up together are exposed to the same home library or household income, so monozygotic and dizygotic twin resemblance cannot be compared for these types of environmental measures. However, a classical twin study can begin to separate the direct effect of the home environment in two cases. First, child twins can be asked to individually rate their own rearing environment (Fig. 4 ). Since individual experiences are correlated with genetic predisposition, monozygotic twins often rate their experiences of the home environment more similarly with each other than dizygotic twins do. Therefore, when child twins can report their own ratings of their rearing environment, these estimates can serve to differentiate monozygotic and dizygotic twins. Twins who are children might not differ in how many books they have in the home, but they will likely differ in how much their parents read to them, or how much their parents monitor their reading. In these cases, the extent to which aspects of children’s rating of their rearing environment do not show entirely environmental influences, in other words, some heritability is measured on the “rearing environment”, this infers that there is a genetic confound, via a passive gene–environment correlation 4 , 19 . Using child twin ratings of their rearing environment, Hanscombe et al. 24 found that 22% of the variance of chaos in the home was attributable to genetic factors, and moreover, 37% of association between chaos in the home and school achievement was due to shared genes. This suggests that this “environmental” variable of chaos in the home, measuring noise and lack of structure in the home, is partially genetically confounded. This means that chaos in the home does not have a completely direct, or causal role, on children’s school achievement.

The second way that the classical twin model can be used to identify the direct effect of the home environment, free of genetic confounding, is by focusing on the environment that adult twins create (see Fig. 4 , but replace “reading ability” with “books in their home” or the like). When twins are adults they can differ in how many books they own and the income of their household, so genetic and environmental influences on their home environments can be studied. These studies quantify genetic and environmental influences on the home environment that twins create 4 , but they do not quantify the influence of these home characteristics on outcomes in their offspring.

Other genetically sensitive designs that can address the direct effect of the rearing environment, after accounting for genetic confounding, are adoption studies, within-family sibling studies, and twin-family studies 25 . In an adoption design, resemblance between adopted children and their biological parents is due to heritability (plus the prenatal environment). In contrast, resemblance between adopted children and their adoptive parents is fully due to the environment that the parents have provided. Another way to examine the rearing environment while partially controlling for genetic confounding is to use non-twin biological siblings within a family 26 , 27 . Because biological siblings, like dizygotic twins, share half of their genes, sibling resemblance on a trait suggests the influence of genetic factors along with some shared environmental influences. However, non-twin siblings can differ on several aspects of the rearing environment such as family size or parental health and age at birth, therefore, any dissimilarity between siblings can help to determine the influences of these non-shared aspects of the rearing environments on a given trait. Sibling designs have also recently incorporated the use of genome-wide PGS which strengthen their ability to control for confounding by disentangling direct genetic influences from gene–environment correlations 28 , 29 . PGS designs are discussed in more detail, below.

Twin-family studies include twins and their family members, like young twins and their parents, or adult twins and their children. The latter, referred to as children-of-twins design (Fig. 5 ), is particularly suitable to study the effect of children’s rearing environment, free of genetic confounding 21 . Put simply, consider a mother who has an identical twin sister. The mother’s son shares half of his genetic variants with his mother, but also with his aunt. If for a given trait he resembles his mother as much as his aunt, this suggests that the resemblance is fully due to shared genes. Conversely, if he is more like his mother than aunt, this demonstrates that the resemblance between mother and son is at least partially due to the environment provided by his mother (see Footnote 3 in the Supplementary Notes ). There are even more complex extended twin family designs, described well in Keller et al. 30 and McAdams et al. 31 .

In the given example, the (adult) twins are sisters. The genetic transmission (left hand side) is fixed at 0.50 because parents and children share 50% of their genome. The other set of genes that influence the child trait (bottom left) are genetic influences that explain variance in the child trait but not the parent trait. The crucial test for presence of environmental transmission is whether the p-path is significant. Note that ‘child’ can refer to child or adult offspring. See, for the full and detailed model, ref. 31 . Figure by ref. 66 available at https://bit.ly/2D0aNYJ under a CC BY 4.0 license.

In sum, genetically sensitive designs can assess whether the rearing environment is influencing children’s outcomes, outside of genetic confounds. Although they are observational and hence cannot establish causality, or the absence thereof, they can strongly infer causality above and beyond the majority of typical observational studies. An important point to make is if a genetically sensitive study suggests no direct causality of the rearing environment on children’s outcomes, it does not imply that intervening is pointless. Successful parenting interventions are able to experimentally induce changes in parents’ skills or behaviors, which then causally improve child outcomes. Thus, observational studies, such as all the genetically sensitive designs described here, and experimental studies (preferably randomized controlled trials 32 ) answer related but different questions: the first on “what is”, so causality in the natural situation, and the second on “what could be”, so causality due to intervening 33 , 34 .

Returning to genetically sensitive designs, the disadvantage is that they require access to such data, which are challenging to collect and analyze. We note for a reader interested in using twin data to better answer their questions about the direct role of the rearing environment, twin datasets are increasingly becoming publically available. For example, TwinLife ( https://www.twin-life.de/en ), TEDS ( http://www.teds.ac.uk/researchers ), NLSY kinship links ( http://nlsy-links.github.io/NlsyLinks/ ), Netherlands Twin Register ( http://tweelingenregister.vu.nl/research ), and others are available online or via application. In addition, there is a data sharing culture in the behavioral genetics community, and most will likely share when asked. We suggest that researchers consider using these resources to better test their research questions.

PGS designs

A new avenue to study intertwined genetic and environmental effects employs genome-wide PGS. This method relies on genome-wide association studies (GWASs) which pinpoint genetic variants (i.e., single nucleotide polymorphisms (SNPs)) that are linked to a trait (Fig. 6 ). The most powerful GWAS to date ( N  > 1 million) has identified 1271 genetic variants associated with educational attainment 35 . Each of them has a tiny effect, but these tiny effects can be summed in a PGS. The PGS, calculated for all (unrelated) individuals in an independent sample, explains 12% of the variance in educational attainment. Note that twin studies estimate the heritability of educational attainment at 40% 36 , so the PGS currently captures less than one-third of this; the remainder is the “missing heritability” 37 .

Left panel: A published genome-wide association study (GWAS) serves as an external database. In an extremely large sample, a GWAS estimates tiny associations ( \({\hat{\mathrm b}}\) ) between the trait of interest and millions of genetic variants. Specifically, the genetic variants studied are single-nucleotide polymorphisms (SNPs), located across the genome. Middle panel: Polygenic scoring can be done in a sample that was not part of the GWAS. For each individual in this sample, the SNP effects ( \({\hat{\mathrm b}}\) ) are multiplied by the number of trait-associated alleles (0, 1, or 2) the person carries. These values are summed across all SNPs to arrive at the individual’s PGS. Right panel: The resulting PGSs across individuals in that sample are normally distributed. If the trait of interest is a disorder, like ADHD, the individuals in the right tail have the highest genetic risk for developing ADHD. PGSs are not yet strong enough for predictions at the individual level, but see the main text for examples of how PGSs advance science at the group level. Figure adapted from ref. 69 . Figure by ref. 66 available at https://bit.ly/2BPcCXP under a CC BY 4.0 license.

As we speak, novel methods are being designed to disentangle nature and nurture that draw on PGS. Below, we list some examples of recent developments. First, Dolan et al. 38 bring PGS into the classical twin design. By doing so, one can estimate the gene–environment correlation, rather than assume it is absent. Second, Lee et al. 35 and Selzam et al. 29 found that for cognitive traits, the predictive power of a PGS within a family was about 50% lower than across unrelated individuals. The attenuation of the PGS’ predictive power within families suggests that passive gene–environment correlations (as captured by the PGS) contribute to children’s cognitive development. As a third example, both Kong et al. 39 and Bates et al. 40 separately proposed the same design incorporating parental and offspring PGS to disentangle environmental transmission from genetic transmission (i.e., account for the genetic confound between the home environment and child outcomes). In both cases, the researchers split the genetic variants of the parents in half—those that the parent had and had not transmitted to the offspring—and calculated for each half the PGS for educational attainment (Fig. 7 ). The researchers do this because of the biological fact that a parent only transmits a random half of their genes to their child. And for this design to work, both parents and their child must be included (but see ref. 41 for a work around). Amazingly, what the researchers found was both sets of parent PGS predicted adult offspring’s educational attainment. The predictive value of the transmitted PGS was unsurprising, as this captures directly transmitted genetic effects. But the predictive value of the non-transmitted PGS was not certain. If non-transmitted PGS influence children’s traits, this effect must be environmental, likely acting through rearing behaviors that affect the child’s development. Kong et al. 39 aptly coined this genetic effect through the rearing environment “genetic nurturing”. Belsky et al. 42 did a similar analysis but with an updated PGS score. Interestingly, when this design is expanded to include grandparents, there is little evidence for genetic nurturing from the grandparent generation 43 . Fourth, Wertz et al. 44 incorporated both PGS of mothers and children, as well as direct measures of parenting. They showed that mothers’ cognitive stimulation explained the relation of the maternal non-transmitted PGS to child educational attainment. This indicated that there is a direct environmental transmission of parenting on children’s outcomes, unconfounded by correlated genetic transmission. Finally, de Zeeuw et al. 45 and Willoughby et al. 46 both used the full genetic-nurturing design (employing DNA of children and both parents) and found (thereby replicated) genetic-nurturing effects on adults’ educational attainment. Crucially, for outcomes in childhood, academic achievement and ADHD-symptoms, Zeeuw et al. 45 only found direct genetic effects; no genetic nurturing. They concluded that a large contributor to why the rearing environment predicts child outcomes may well be intergenerational transmission of genetic effects.

In this design, one needs genotypes of parents and offspring, and a measured trait in the offspring generation only. The trait in the parents, for example educational attainment, is unobserved and indexed by a polygenic score of, in this example, educational attainment. The child receives half of the genotypes of father (top left) and mother (top right) and these transmitted alleles influence the child trait directly. The parental alleles that the child does not receive can still influence the child trait indirectly, via genetically influenced behaviors in the parents (denoted by the dotted genetic-nurturing paths). Genetic nurturing is present if the polygenic score of the untransmitted alleles explains a significant proportion of the variance in the child trait. The proportion of variance explained by the polygenic score of the transmitted alleles include both genetic nurturing and direct effects. Note that ‘child’ can refer to child or adult offspring. T = transmitted, NT = non-transmitted. Figure adapted from ref. 39 . Figure by ref. 66 available at https://bit.ly/2PjpkRu under a CC BY 4.0 license.

At the moment, measured genetic variants only explain small proportions of variance and the papers mentioned above may be seen by behavioral researchers as only a proof-of-principle. Nevertheless, these exciting developments will gain in strength when increasingly larger GWASs of all sorts of traits yield more refined PGS. By this we mean that PGSs will begin to explain more and more portions of the variance in outcomes we are interested in, with the hope that eventually they will reach the theoretical upper limit of SNP heritability. Even then, using them as a genetic control (i.e., as a covariate) will continue to underestimate the total genetic effects we are looking to control. PGSs account for only one type of genetic effect, namely common variants. There is increasing evidence that traits such as educational attainment are influenced by not only common variants, but also rare variants 47 , 48 . Another concern is that new work is indicting that a PGS is not a measure of only genetic variance. Instead, it likely represents not only causal genetic effects, but genetic ancestry, assortative mating, gene x environment interactions, direct environmental influences (i.e., genetic nurture), and environmental confounds from, for example, SES 49 , 50 . Therefore, a measure of genes (i.e., a PGS) can predict trait variance via environmental routes. This parallels our earlier notion that a measure of the environment can predict trait variance via genetic routes.

In summary, at the moment the PGS is not a perfect “genetic control”, as it does not account for all of the genetic effects and also accounts for other effects, including the very environment we are interested in. But, we believe that next to no control, using a PGS as a statistical control is still better. Costs of genotyping are falling and the number of cohorts with genotype data is growing 51 . We predict that in the not-so-far future, using simply and cheaply collected genotypic information will become a regular part of the behavioral researchers’ data collection protocol, especially as the predictive validity of the PGSs increases. This means that PGSs will allow researchers to partly control for genetic confounds in their models. We foresee that it will be easier to use PGSs than rely on genetically sensitive designs.

Genetic-proxy control designs: the Familial Control Method

The designs discussed above are the current gold-standards. However, as these types of samples discussed above are not currently easy to collect and analyze, we propose here a useful work around 52 , 53 . Our colleagues can measure the same trait in both the parents as the child, and use the paternal and maternal traits as covariates. We advise to assess the traits in both parents (but acknowledge the challenge that brings), because the child shares only 50% of their genes with one parent, but all of their genes with both parents. Hence, both parents are needed to best tag the child’s genetic liability. The parental traits, included as two covariates, then serve as a proxy for the familial transmission, including genetic transmission. In doing so, you have a proxy control for the familial effect. Hence, we term this method the Familial Control Method.

The Familial Control Method is designed for traits that are mostly transmitted from parent to child through genes rather than the environment, like reading ability 54 , 55 (see Footnote 4 in the Supplementary Notes ). Van Bergen et al. 53 capitalized on this in studying whether children’s reading ability is influenced by the home literacy environment, like reading habits of the parents and the number of books in the home. Analyses consisted of straight-forward step-wise regression analyses, illustrated in Fig. 8 . The home literacy environment correlated with children’s reading ability, but for most home-literacy indicators the effect was no longer significant after accounting for the reading ability of the parents. This suggests genetic confound rather than a genuine environmental effect. The one exception was the number of books children grow up with, which did explain variance over and beyond parents’ reading skills (Fig. 8 ). This suggests a genuine environmental effect on children’s reading by the number of books itself, or something related, like the value that the family places on reading 45 .

The findings that are depicted here come from van Bergen et al. 53 . The key question is whether the environmental measure explains variance beyond the familial effect, as this indicates a genuine environmental effect. In the example given, this was 5% and significant. This was negligible and non-significant for the other environmental measures reported in ref. 53 . Figure by ref. 66 available at https://bit.ly/2Pfjelh under a CC BY 4.0 license.

A similar approach was taken by Hart et al. 52 in studying the effect of the home numeracy environment on children’s math ability. When a parent’s math ability was included in the model, some effects of aspects of the home numeracy environment on children’s math ability were attenuated, but most held up. A note of caution is that the skills of only one parent could be obtained and controlled for, so the study lacked a proxy for the genetic liability passed on by the other parent. The authors concluded that doing more math-related activities with your children does seem to directly boost their math.

We advise researchers who are interested in applying the Familial Control Method to search first in the literature for adoption and twin-family studies. Such studies with the outcome trait of interest (e.g., reading ability) assessed in both the parent and the offspring generation, test whether parent to offspring transmission is mainly genetic or environmental in nature 54 , 55 . However, such studies are scarce. If such studies for the trait of interest do not exist, a good starting point are classical twin studies. Traits with no or a small influence of the shared environment (referred to as C), like neurological traits, are more likely to be transmitted just genetically compared to traits with large shared-environment influences, like social values. Results of meta-analyses of twin studies on a very large number of traits can be found in Polderman et al. 2 and the accompanying webtool ( http://match.ctglab.nl/ ).

The Familial Control Method, using a parental trait as genetic proxy, is not watertight, and certain assumptions must be made for it to be effective for your research question (see Footnote 5 in the Supplementary Notes ). First, if, for a certain trait, parent–child resemblance is not only due to genetic transmission but also environmental transmission, the Familial Control Method can be too conservative, as it also takes away some of the variance due to true environmental effects. However, one could argue that for many situations, being slightly too cautious in causal claims about environmental influences is less harmful than being too lax. However, this might not be the case for all researchers, and we encourage behavioral researchers to consider if being too conservative is actual harmful (e.g., for the effect of an unsafe home environment on child psychopathology) Second, as mentioned earlier, the trait measured in the parents should be the same or highly similar as the trait measured in the child. This means that traits which are not at least reasonably the same in childhood as adulthood (i.e., across birth cohorts and across the lifespan) would not work in this design. So the trait should be at least reasonably measurement invariant and relatedly, show reasonable genetic stability. Fortunately, for many phenotypes, children’s phenotypes are simply developmental precursors to the adult phenotypes (e.g., for reading ability 56 , and for ADHD 57 ). A researcher must decide if the mentioned assumptions are appropriate for their trait of interest, but fortunately we do believe that these assumptions are reasonable for most to make. Third, correlations among the parent and child trait and the environmental measure of interest will be attenuated by measurement error. To reduce measurement error, one can do regressions according to the Familial Control Method in a structural equation modeling framework, with multiple indicators per construct. One can fit a model with as the outcome the latent child trait of interest, and as (correlated) predictors, the latent traits of both parents and the environmental measure of interest. If dropping the regression path ‘environmental measure → child outcome’ leads to a significantly worse model fit, this implies that the environmental measure is associated with the outcome above and beyond the familial effect. If the trait of interest is genetically transmitted, this equates to above and beyond genetic confounding, so suggests a direct environmental influence. The effect size here is given by the difference in explained variance in the child outcome of the models with and without the ‘environmental measure → child outcome’ path. Adopting a structural equation modeling framework with latent variables is especially advisable for constructs that are notoriously hard to measure reliably. Another advantage of this framework, compared to stepwise regressions, is that families with missing data can be retained.

It is likely the case that for most behavioral researchers interested in the direct role of the rearing environment, the Familial Control Method is currently the most feasible proxy genetic control. It does not require data of twin or adoption families, nor collecting DNA samples. In terms of prediction, parental traits capture more of the variance in children’s outcome than polygenic scores, so likely also capture more of the genetic confound. For the example of reading ability, it has been found that the abilities of both of the parents explain 21% of the ability of children 58 . In comparison, polygenic scores (based on the educational-attainment GWAS) have been found to explain only 2–5% of reading ability in children 59 , and more recently 5–14% of “educational achievement” (including reading, writing, speaking, listening, and mathematics) in ages 7 to 16 years 60 . Certainly this proportion of variance explained from simple polygenic scores is not trivial, and the predictive ability of polygenic scores is anticipated to increase in the coming years. However, for most behavioral scientists the trait in the parents is not only easier to measure, but currently also a better predictor. On a related note, the value of parental traits as predictors of child outcomes has been used for decades in studying precursors of developmental disorders. In such family-risk studies, children with a family history of say dyslexia, attention-deficit/hyperactivity disorder or autism are followed from an early age, before the disorder manifests itself. These children have an increased risk to develop the disorder 61 , 62 .

Other proxy control designs

Other proxy controls such as sociodemographic factors (e.g., SES) have been used ubiquitously, but these statistical adjustments are not capable of accounting for genetic confounding as adequately as the Familial Control Method, for several reasons. First, although sociodemographic factors such as educational attainment have been significantly associated with genetic factors through twin studies (40% 36 ) and GWAS (~14% 35 ), the estimates are less than unity which indicates that genetic influences are not entirely responsible for individual differences in SES. Indeed, work examining the intergenerational transmission of SES has suggested that both genetic and environmental transmission occurs 63 . In this scenario where SES is transmitted through genetic and environmental pathways, when controlling for SES in data analyses, a proportion of variance attributable to other background or environmental factors is also being controlled for in the model, unintentionally leading to reduced associations between potentially important family-level predictors and child outcomes. In other words, you’d be throwing the baby out with the bathwater.

On the other hand, controlling for SES does not actually control for all of the genetic confounding. Say a researcher is interested in controlling for genetic confounding when examining the direct influence of books in the home on children’s reading. Parental SES is a proxy for parental reading skill, but not a perfect correlate (average correlation is 0.26 64 ). Controlling for parental SES would not control for all of the potential genetic confounds on the association between books in the home and children’s reading ability. In conclusion, when controlling for SES, other potential sources of environmental variance are also being removed from the prospective models, and at the same time would not capture the extent of genetic confounding. We believe this would happen with other proxy control measures as well, outside of the Familial Control Method described above.

Here we have laid out numerous ways that genetic confounding can be controlled for when examining the rearing environment, summarized in a decision flowchart (Fig. 9 ). We can certainly foresee times that none of these options are possible. Therefore, we conclude that in those instances, our colleagues need to clearly mention the possible genetic confounding as a limitation, and to be cautious with any environmental causal statements which could lead to unnecessary parent blaming or to interventions that are a waste of time and resources. To return to our first example, expecting all homes to have plenty of books is an idealistic goal, as it would surround all children with the opportunity to read if they wished. But unfortunately, having the opportunity to read as one wishes does not unlock the code of reading for all children. Reading is a skill that requires direct instruction and practice, and children with a family history of dyslexia themselves have a 45% chance of dyslexia despite adequate instruction and practice 61 . Simply having books around the home is not enough 65 , yet the message that parents are getting is that it is. The take home messages from that are that either parents who do not have the resources for a home library are hurting their children, or parents with children struggling to read are at blame because they did not have quite enough books in the home. This is unfair and inaccurate. In the end, we believe that it is important to discover true environmental effects as well as how genes and environments interplay, especially when malleable, because then we can focus as a field on creating and testing interventions that have a greater chance of directly improving children’s outcomes.

DK = don’t know. Figure by ref. 66 available at https://bit.ly/3gkM6Et under a CC BY 4.0 license.

Reporting summary

Further information on experimental design is available in the Nature Research Reporting Summary linked to this paper.

Data availability

Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.

Code availability

Code sharing not applicable to this article as no codes were generated during the current study.

Sikora, J., Evans, M. & Kelley, J. Scholarly culture: how books in adolescence enhance adult literacy, numeracy and technology skills in 31 societies. Soc. Sci. Res. 77 , 1–15 (2019).

Article   PubMed   Google Scholar  

Polderman, T. J. et al. Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nat. Genet. 47 , 702 (2015).

Article   CAS   PubMed   Google Scholar  

Turkheimer, E. Three laws of behavior genetics and what they mean. Curr. Dir. Psychol. Sci. 9 , 160–164 (2000).

Article   Google Scholar  

Kendler, K. S. & Baker, J. H. Genetic influences on measures of the environment: a systematic review. Psychol. Med. 37 , 615 (2007).

Klahr, A. M. & Burt, S. A. Elucidating the etiology of individual differences in parenting: a meta-analysis of behavioral genetic research. Psychol. Bull. 140 , 544 (2014).

Plomin, R., DeFries, J. C. & Loehlin, J. C. Genotype-environment interaction and correlation in the analysis of human behavior. Psychol. Bull. 84 , 309–322 (1977).

Prinzie, P., Stams, G. J. J., Deković, M., Reijntjes, A. H. & Belsky, J. The relations between parents’ Big Five personality factors and parenting: a meta-analytic review. J. Pers. Soc. Psychol. 97 , 351 (2009).

Magnusson, D., & Stattin, H. In Handbook of Child Psychology: Theoretical Models of Human Development (eds Damon, W. & Lerner, R. M.) 685–759 (John Wiley & Sons Inc., 1998).

Baltes, P. B. & Baltes, M. M. In Successful Aging: Perspectives From the Behavioral Sciences (eds Baltes, P. B. & Baltes, M. M.) (Cambridge University Press, 1990).

Lemery-Chalfant, K., Kao, K., Swann, G. & Goldsmith, H. H. Childhood temperament: passive gene-environment correlation, gene-environment interaction, and the hidden importance of the family environment. Dev. Psychopathol. 25 , 51 (2013).

Article   PubMed   PubMed Central   Google Scholar  

Burt, S. A. Genes and popularity: evidence of an evocative gene-environment correlation. Psychol. Sci. 19 , 112–113 (2008).

Hicks, B. M. et al. Gene-environment correlation in the development of adolescent substance abuse: selection effects of child personality and mediation via contextual risk factors. Dev. Psychopathol. 25 , 119 (2013).

Scarr, S. & McCartney, K. How people make their own environments: a theory of genotype → environment effects. Child Dev. 54 , 424–435 (1983).

CAS   PubMed   Google Scholar  

Maloney, E. A., Ramirez, G., Gunderson, E. A., Levine, S. C. & Beilock, S. L. Intergenerational effects of parents’ math anxiety on children’s math achievement and anxiety. Psychol. Sci. 26 , 1480–1488 (2015).

Wang, Z. et al. Who is afraid of math? Two sources of genetic variance for mathematical anxiety. J. Child Psychol. Psychiatry 55 , 1056–1064 (2014).

Gilman, S. E. et al. Parental smoking and adolescent smoking initiation: an intergenerational perspective on tobacco control. Pediatrics 123 , e274–e281 (2009).

Vink, J. M., Willemsen, G. & Boomsma, D. I. Heritability of smoking initiation and nicotine dependence. Behav. Genet. 35 , 397–406 (2005).

Thomas, M. S., Kovas, Y., Meaburn, E. & Tolmie, A. What can the study of genetics offer to educators? Mind Brain Educ. 9 , 1–9 (2015).

Article   CAS   Google Scholar  

Plomin, R. & Bergeman, C. S. The nature of nurture: genetic influence on “environmental” measures. Behav. Brain Sci. 14 , 373–386 (1991).

D’Onofrio, B. M., Turkheimer, E. N., Eaves, L. J. & Corey, L. A. The role of Children of Twins design in elucidating causal relationships between parent characteristics and child outcomes. J. Child Psychol. Psychiatry 44 , 1130–1144 (2003).

McAdams, T. A. et al. Accounting for genetic and environmental confounds in associations between parent and child characteristics: a systematic review of children-of-twins studies. Psychol. Bull. 140 , 1138 (2014).

Sherlock, J. M. & Zietsch, B. P. Longitudinal relationships between parents’ and children’s behavior need not implicate the influence of parental behavior and may reflect genetics: comment on Waldinger and Schulz (2016). Psychol. Sci. 29 , 154–157 (2018).

Knopik, V. S., Neiderhiser, J. M., DeFries, J. C. & Plomin, R. Behavioral Genetics (Macmillan Higher Education, 2017).

Hanscombe, K. B., Haworth, C., Davis, O. S. P., Jaffee, S. R. & Plomin, R. Chaotic homes and school achievement: a twin study. J. Child Psychol. Psychiatry 52 , 1212–1220 (2011).

D’Onofrio, B. M., Lahey, B. B., Turkheimer, E. & Lichtenstein, P. Critical need for family-based, quasi-experimental designs in integrating genetic and social science research. Am. J. Public Health 103 , S46–S55 (2013).

Petersen, A. H. & Lange, T. What is the causal interpretation of sibling comparison designs? Epidemiology 31 , 75–81 (2020).

Rowe, D. C. & Herstand, S. E. Familial influences on television viewing and aggression: a sibling study. Aggress. Behav. 12 , 111–120 (1986).

Brumpton, B. et al. Avoiding dynastic, assortative mating, and population stratification biases in Mendelian randomization through within-family analyses. Nat. Commun. 11 , 1–13 (2020).

Selzam, S. et al. Comparing within-and between-family polygenic score prediction. Am. J. Hum. Genet. 105 , 351–363 (2019).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Keller, M. C., Medland, S. E. & Duncan, L. E. Are extended twin family designs worth the trouble? A comparison of the bias, precision, and accuracy of parameters estimated in four twin family models. Behav. Genet. 40 , 377–393 (2010).

McAdams, T. A. et al. Revisiting the children-of-twins design: improving existing models for the exploration of intergenerational associations. Behav. Genet. 48 , 397–412 (2018).

Shadish, W. R., Cook, T. D. & Campbell, D. T. Experimental and Quasi-Experimental Designs for Generalized Causal Influence (Houghton Mifflin Company, 2002).

Plomin, R., Shakeshaft, N. G., McMillan, A. & Trzaskowski, M. Nature, nurture, and expertise. Intelligence 45 , 46–59 (2014).

van Bergen, E. et al. Why do children read more? The influence of reading ability on voluntary reading practices. J. Child Psychol. Psychiatry 59 , 1205–1214 (2018).

Lee, J. J. et al. Gene discovery and polygenic prediction from a genome-wide association study of educational attainment in 1.1 million individuals. Nat. Genet. 50 , 1112–1121 (2018).

Branigan, A. R., McCallum, K. J. & Freese, J. Variation in the heritability of educational attainment: an international meta-analysis. Soc. Forces 92 , 109–140 (2013).

Maher, B. The case of the missing heritability. Nature 465 , 18–21 (2008).

Dolan, C. V., Huijskens, R. C., Minica, C. C., Neale, M. C. & Boomsma, D. I. Incorporating polygenic scores in the twin model to estimate genotype-environment covariance: exploration of statistical power. Preprint at https://doi.org/10.1101/702738 (2019).

Kong, A. et al. The nature of nurture: effects of parental genotypes. Science 359 , 424–428 (2018).

Bates, T. C. et al. The nature of nurture: using a virtual-parent design to test parenting effects on children’s educational attainment in genotyped families. Twin Res. Hum. Genet. 21 , 73–83 (2018).

Young, A. I. et al. Mendelian imputation of parental genotypes for genome-wide estimation of direct and indirect genetic effects. Preprint at https://doi.org/10.1101/2020.07.02.185199 (2020).

Belsky, D. W. et al. Genetic analysis of social-class mobility in five longitudinal studies. Proc. Natl Acad. Sci. USA 115 , E7275–E7284 (2018).

Liu, H. Social and genetic pathways in multigenerational transmission of educational attainment. Am. Sociol. Rev. 83 , 278–304 (2018).

Wertz, J. et al. Using DNA from mothers and children to study parental investment in children’s educational attainment. Child Dev. 91 , 1745–1761 (2020).

de Zeeuw, E. L. et al. Intergenerational transmission of education and ADHD: effects of parental genotypes. Behav. Genet. 50 , 221–232 (2020).

Willoughby, E. A., McGue, M., Iacono, W. G., Rustichini, A. & Lee, J. J. The role of parental genotype in predicting offspring years of education: evidence for genetic nurture. Mol. Psychiatry 1–9, https://www.nature.com/articles/s41380-019-0494-1 (2019).

Cesarini, D. & Visscher, P. M. Genetics and educational attainment. npj Sci. Learn. 2 , 1–7 (2017).

Kendall, K. M. et al. Cognitive performance and functional outcomes of carriers of pathogenic copy number variants: analysis of the UK Biobank. Br. J. Psychiatry 214 , 297–304 (2019).

Trejo, S. & Domingue, B. W. Genetic nature or genetic nurture? Introducing social genetic parameters to quantify bias in polygenic score analyses. Biodemography Soc. Biol. 64 , 187–215 (2018).

Mostafavi, H. et al. Variable prediction accuracy of polygenic scores within an ancestry group. Elife 9 , e48376 (2020).

Evans, D. M., Moen, G.-H., Hwang, L.-D., Lawlor, D. A. & Warrington, N. M. Elucidating the role of maternal environmental exposures on offspring health and disease using two-sample Mendelian randomization. Int. J. Epidemiol. 48 , 861–875 (2019).

Hart, S. A., Ganley, C. M. & Purpura, D. J. Understanding the home math environment and its role in predicting parent report of children’s math skills. PLoS ONE 11 , e0168227 (2016).

Article   PubMed   PubMed Central   CAS   Google Scholar  

van Bergen, E., van Zuijen, T., Bishop, D. & de Jong, P. F. Why are home literacy environment and children’s reading skills associated? What parental skills reveal. Read. Res. Q. 52 , 147–160 (2017).

Swagerman, S. C. et al. Genetic transmission of reading ability. Brain Lang. 172 , 3–8 (2017).

Wadsworth, S. J., Corley, R. P., Hewitt, J. K., Plomin, R. & DeFries, J. C. Parent-offspring resemblance for reading performance at 7, 12 and 16 years of age in the Colorado Adoption Project. J. Child Psychol. Psychiatry 43 , 769–774 (2002).

Wadsworth, S. J., Corley, R. P., Hewitt, J. K. & DeFries, J. C. Stability of genetic and environmental influences on reading performance at 7, 12, and 16 years of age in the Colorado Adoption Project. Behav. Genet. 31 , 353–359 (2001).

Kan, K.-J. et al. Genetic and environmental stability in attention problems across the lifespan: evidence from the Netherlands twin register. J. Am. Acad. Child Adolesc. Psychiatry 52 , 12–25 (2013).

van Bergen, E., Bishop, D., van Zuijen, T. & de Jong, P. F. How does parental reading influence children’s reading? A study of cognitive mediation. Sci. Stud. Read. 19 , 325–339 (2015).

Selzam, S. et al. Genome-wide polygenic scores predict reading performance throughout the school years. Sci. Stud. Read. 21 , 334–349 (2017).

von Stumm, S. et al. Predicting educational achievement from genomic measures and socioeconomic status. Dev. Sci. 23 , e12925 (2020).

Snowling, M. J. & Melby-Lervåg, M. Oral language deficits in familial dyslexia: a meta-analysis and review. Psychol. Bull. 142 , 498 (2016).

Musser, E. D. et al. Shared familial transmission of autism spectrum and attention‐deficit/hyperactivity disorders. J. Child Psychol. Psychiatry 55 , 819–827 (2014).

Björklund, A., Jäntti, M. & Solon, G. Nature and nurture in the intergenerational transmission of socioeconomic status: evidence from Swedish children and their biological and rearing parents. B.E. J. Econ. Anal. Policy 7 , https://www.nber.org/papers/w12985 (2007).

Sirin, S. R. Socioeconomic Status and Academic Achievement: A Meta-Analytic Review of Research. Rev. Educ. Res. 75 , 417–453 (2016).

Kim, J. S. The effects of a voluntary summer reading intervention on reading activities and reading achievement. J. Educ. Psychol. 99 , 505 (2007).

Hart, S. A., Little, C. & van Bergen. Genetic confounding figures. Figshare . https://figshare.com/account/home#/collections/5080187 (2020).

Falconer, D. S. Introduction to Quantitative Genetics (Ronald Press, NY, New York, 1960).

Rayner, C. P is for polygenic risk scores. EDITLab Blog, KCL. https://blogs.kcl.ac.uk/editlab/2018/07/31/p-is-for-polygenic-risk-scores/ (2018).

Belsky, D. W. & Harden, K. P. Phenotypic annotation: using polygenic scores to translate discoveries from genome-wide association studies from the top down. Curr. Dir. Psychol. Sci. 28 , 82–90 (2019).

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Acknowledgements

S.A.H. is supported by Eunice Kennedy Shriver National Institute of Child Health & Human Development Grants HD052120 and HD095193. Views expressed herein are those of the authors and have neither been reviewed nor approved by the granting agencies. E.vB. is supported by NWO VENI fellowship 451-15-017 (“Decoding the gene-environment interplay of reading ability”) and ZonMw grant 531003014 (“Genetics as a research tool: A natural experiment to elucidate the causal effects of social mobility on health”). She is a member of the Consortium on Individual Development (CID; NWO Gravitation grant 024.001.003) and of Research Institute LEARN!.

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Hart, S.A., Little, C. & van Bergen, E. Nurture might be nature: cautionary tales and proposed solutions. npj Sci. Learn. 6 , 2 (2021). https://doi.org/10.1038/s41539-020-00079-z

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Chapter 4. Genetics and Evolution

4.1 The Nature-Nurture Question

Eric Turkheimer

People have a deep intuition about what has been called the “nature–nurture question.” Some aspects of our behavior feel as though they originate in our genetic makeup, while others feel like the result of our upbringing or our own hard work. The scientific field of behavior genetics attempts to study these differences empirically, either by examining similarities among family members with different degrees of genetic relatedness, or, more recently, by studying differences in the DNA of people with different behavioral traits. The scientific methods that have been developed are ingenious, but often inconclusive. Many of the difficulties encountered in the empirical science of behavior genetics turn out to be conceptual, and our intuitions about nature and nurture get more complicated the harder we think about them. In the end, it is an oversimplification to ask how “genetic” some particular behavior is. Genes and environments always combine to produce behavior, and the real science is in the discovery of how they combine for a given behavior.

Learning Objectives

• Understand what the nature–nurture debate is and why the problem fascinates us.
• Understand why nature–nurture questions are difficult to study empirically.
• Know the major research designs that can be used to study nature–nurture questions.
• Appreciate the complexities of nature–nurture and why questions that seem simple turn out not to have simple answers.

Introduction

There are three related problems at the intersection of philosophy and science that are fundamental to our understanding of our relationship to the natural world: the mind–body problem, the free will problem, and the nature–nurture problem. These great questions have a lot in common. Everyone, even those without much knowledge of science or philosophy, has opinions about the answers to these questions that come simply from observing the world we live in. Our feelings about our relationship with the physical and biological world often seem incomplete. We are in control of our actions in some ways, but at the mercy of our bodies in others; it feels obvious that our consciousness is some kind of creation of our physical brains, at the same time we sense that our awareness must go beyond just the physical. This incomplete knowledge of our relationship with nature leaves us fascinated and a little obsessed, like a cat that climbs into a paper bag and then out again, over and over, mystified every time by a relationship between inner and outer that it can see but can’t quite understand.

It may seem obvious that we are born with certain characteristics while others are acquired, and yet of the three great questions about humans’ relationship with the natural world, only nature–nurture gets referred to as a “debate.” In the history of psychology, no other question has caused so much controversy and offense: We are so concerned with nature–nurture because our very sense of moral character seems to depend on it. While we may admire the athletic skills of a great basketball player, we think of his height as simply a gift, a payoff in the “genetic lottery.” For the same reason, no one blames a short person for his height or someone’s congenital disability on poor decisions: To state the obvious, it’s “not their fault.” But we do praise the concert violinist (and perhaps her parents and teachers as well) for her dedication, just as we condemn cheaters, slackers, and bullies for their bad behavior.

The problem is, most human characteristics aren’t usually as clear-cut as height or instrument-mastery, affirming our nature–nurture expectations strongly one way or the other. In fact, even the great violinist might have some inborn qualities—perfect pitch, or long, nimble fingers—that support and reward her hard work. And the basketball player might have eaten a diet while growing up that promoted his genetic tendency for being tall. When we think about our own qualities, they seem under our control in some respects, yet beyond our control in others. And often the traits that don’t seem to have an obvious cause are the ones that concern us the most and are far more personally significant. What about how much we drink or worry? What about our honesty, or religiosity, or sexual orientation? They all come from that uncertain zone, neither fixed by nature nor totally under our own control.

One major problem with answering nature-nurture questions about people is, how do you set up an experiment? In nonhuman animals, there are relatively straightforward experiments for tackling nature–nurture questions. Say, for example, you are interested in aggressiveness in dogs. You want to test for the more important determinant of aggression: being born to aggressive dogs or being raised by them. You could mate two aggressive dogs—angry Chihuahuas—together, and mate two nonaggressive dogs—happy beagles—together, then switch half the puppies from each litter between the different sets of parents to raise. You would then have puppies born to aggressive parents (the Chihuahuas) but being raised by nonaggressive parents (the Beagles), and vice versa, in litters that mirror each other in puppy distribution. The big questions are: Would the Chihuahua parents raise aggressive beagle puppies? Would the beagle parents raise  non aggressive Chihuahua puppies? Would the puppies’  nature  win out, regardless of who raised them? Or… would the result be a combination of nature  and  nurture? Much of the most significant nature–nurture research has been done in this way (Scott & Fuller, 1998), and animal breeders have been doing it successfully for thousands of years. In fact, it is fairly easy to breed animals for behavioral traits.

With people, however, we can’t assign babies to parents at random, or select parents with certain behavioral characteristics to mate, merely in the interest of science (though history does include horrific examples of such practices, in misguided attempts at “eugenics,” the shaping of human characteristics through intentional breeding). In typical human families, children’s biological parents raise them, so it is very difficult to know whether children act like their parents due to genetic (nature) or environmental (nurture) reasons. Nevertheless, despite our restrictions on setting up human-based experiments, we do see real-world examples of nature-nurture at work in the human sphere—though they only provide partial answers to our many questions.

The science of how genes and environments work together to influence behavior is called  behavioral genetics . The easiest opportunity we have to observe this is the  adoption study . When children are put up for adoption, the parents who give birth to them are no longer the parents who raise them. This setup isn’t quite the same as the experiments with dogs (children aren’t assigned to random adoptive parents in order to suit the particular interests of a scientist) but adoption still tells us some interesting things, or at least confirms some basic expectations. For instance, if the biological child of tall parents were adopted into a family of short people, do you suppose the child’s growth would be affected? What about the biological child of a Spanish-speaking family adopted at birth into an English-speaking family? What language would you expect the child to speak? And what might these outcomes tell you about the difference between height and language in terms of nature-nurture?

Another option for observing nature-nurture in humans involves  twin studies . There are two types of twins: monozygotic (MZ) and dizygotic (DZ). Monozygotic twins, also called “identical” twins, result from a single zygote (fertilized egg) and have the same DNA. They are essentially clones. Dizygotic twins, also known as “fraternal” twins, develop from two zygotes and share 50% of their DNA. Fraternal twins are ordinary siblings who happen to have been born at the same time. To analyze nature–nurture using twins, we compare the similarity of MZ and DZ pairs. Sticking with the features of height and spoken language, let’s take a look at how nature and nurture apply: Identical twins, unsurprisingly, are almost perfectly similar for height. The heights of fraternal twins, however, are like any other sibling pairs: more similar to each other than to people from other families, but hardly identical. This contrast between twin types gives us a clue about the role genetics plays in determining height. Now consider spoken language. If one identical twin speaks Spanish at home, the co-twin with whom she is raised almost certainly does too. But the same would be true for a pair of fraternal twins raised together. In terms of spoken language, fraternal twins are just as similar as identical twins, so it appears that the genetic match of identical twins doesn’t make much difference.

Twin and adoption studies are two instances of a much broader class of methods for observing nature-nurture called  quantitative genetics , the scientific discipline in which similarities among individuals are analyzed based on how biologically related they are. We can do these studies with siblings and half-siblings, cousins, twins who have been separated at birth and raised separately (Bouchard, Lykken, McGue, & Segal, 1990; such twins are very rare and play a smaller role than is commonly believed in the science of nature–nurture), or with entire extended families (see Plomin, DeFries, Knopik, & Neiderhiser, 2012, for a complete introduction to research methods relevant to nature–nurture).

For better or for worse, contentions about nature–nurture have intensified because quantitative genetics produces a number called a  heritability coefficient , varying from 0 to 1, that is meant to provide a single measure of genetics’ influence of a trait. In a general way, a heritability coefficient measures how strongly differences among individuals are related to differences among their genes. But beware: Heritability coefficients, although simple to compute, are deceptively difficult to interpret. Nevertheless, numbers that provide simple answers to complicated questions tend to have a strong influence on the human imagination, and a great deal of time has been spent discussing whether the heritability of intelligence or personality or depression is equal to one number or another.

One reason nature–nurture continues to fascinate us so much is that we live in an era of great scientific discovery in genetics, comparable to the times of Copernicus, Galileo, and Newton, with regard to astronomy and physics. Every day, it seems, new discoveries are made, new possibilities proposed. When Francis Galton first started thinking about nature–nurture in the late-19th century he was very influenced by his cousin, Charles Darwin, but genetics  per se  was unknown. Mendel’s famous work with peas, conducted at about the same time, went undiscovered for 20 years; quantitative genetics was developed in the 1920s; DNA was discovered by Watson and Crick in the 1950s; the human genome was completely sequenced at the turn of the 21st century; and we are now on the verge of being able to obtain the specific DNA sequence of anyone at a relatively low cost. No one knows what this new genetic knowledge will mean for the study of nature–nurture, but as we will see in the next section, answers to nature–nurture questions have turned out to be far more difficult and mysterious than anyone imagined.

What Have We Learned About Nature–Nurture?

It would be satisfying to be able to say that nature–nurture studies have given us conclusive and complete evidence about where traits come from, with some traits clearly resulting from genetics and others almost entirely from environmental factors, such as childrearing practices and personal will; but that is not the case. Instead,  everything  has turned out to have some footing in genetics. The more genetically-related people are, the more similar they are—for  everything : height, weight, intelligence, personality, mental illness, etc. Sure, it seems like common sense that some traits have a genetic bias. For example, adopted children resemble their biological parents even if they have never met them, and identical twins are more similar to each other than are fraternal twins. And while certain psychological traits, such as personality or mental illness (e.g., schizophrenia), seem reasonably influenced by genetics, it turns out that the same is true for political attitudes, how much television people watch (Plomin, Corley, DeFries, & Fulker, 1990), and whether or not they get divorced (McGue & Lykken, 1992).

It may seem surprising, but genetic influence on behavior is a relatively recent discovery. In the middle of the 20th century, psychology was dominated by the doctrine of behaviorism, which held that behavior could only be explained in terms of environmental factors. Psychiatry concentrated on psychoanalysis, which probed for roots of behavior in individuals’ early life-histories. The truth is, neither behaviorism nor psychoanalysis is incompatible with genetic influences on behavior, and neither Freud nor Skinner was naive about the importance of organic processes in behavior. Nevertheless, in their day it was widely thought that children’s personalities were shaped entirely by imitating their parents’ behavior, and that schizophrenia was caused by certain kinds of “pathological mothering.” Whatever the outcome of our broader discussion of nature–nurture, the basic fact that the best predictors of an adopted child’s personality or mental health are found in the biological parents he or she has never met, rather than in the adoptive parents who raised him or her, presents a significant challenge to purely environmental explanations of personality or psychopathology. The message is clear: You can’t leave genes out of the equation. But keep in mind, no behavioral traits are completely inherited, so you can’t leave the environment out altogether, either.

Trying to untangle the various ways nature-nurture influences human behavior can be messy, and often common-sense notions can get in the way of good science. One very significant contribution of behavioral genetics that has changed psychology for good can be very helpful to keep in mind: When your subjects are biologically-related, no matter how clearly a situation may seem to point to environmental influence, it is never safe to interpret a behavior as wholly the result of nurture without further evidence. For example, when presented with data showing that children whose mothers read to them often are likely to have better reading scores in third grade, it is tempting to conclude that reading to your kids out loud is important to success in school; this may well be true, but the study as described is inconclusive, because there are genetic  as well as environmental pathways between the parenting practices of mothers and the abilities of their children. This is a case where “correlation does not imply causation,” as they say. To establish that reading aloud causes success, a scientist can either study the problem in adoptive families (in which the genetic pathway is absent) or by finding a way to randomly assign children to oral reading conditions.

The outcomes of nature–nurture studies have fallen short of our expectations (of establishing clear-cut bases for traits) in many ways. The most disappointing outcome has been the inability to organize traits from  more – to  less -genetic. As noted earlier, everything has turned out to be at least  somewhat  heritable (passed down), yet nothing has turned out to be  absolutely  heritable, and there hasn’t been much consistency as to which traits are  more heritable and which are  less  heritable once other considerations (such as how accurately the trait can be measured) are taken into account (Turkheimer, 2000). The problem is conceptual: The heritability coefficient, and, in fact, the whole quantitative structure that underlies it, does not match up with our nature–nurture intuitions. We want to know how “important” the roles of genes and environment are to the development of a trait, but in focusing on “important” maybe we’re emphasizing the wrong thing. First of all, genes and environment are both crucial to  every  trait; without genes the environment would have nothing to work on, and too, genes cannot develop in a vacuum. Even more important, because nature–nurture questions look at the differences among people, the cause of a given trait depends not only on the trait itself, but also on the differences in that trait between members of the group being studied.

The classic example of the heritability coefficient defying intuition is the trait of having two arms. No one would argue against the development of arms being a biological, genetic process. But fraternal twins are just as similar for “two-armedness” as identical twins, resulting in a heritability coefficient of zero for the trait of having two arms. Normally, according to the heritability model, this result (coefficient of zero) would suggest all nurture, no nature, but we know that’s not the case. The reason this result is not a tip-off that arm development is less genetic than we imagine is because people  do not vary  in the genes related to arm development—which essentially upends the heritability formula. In fact, in this instance, the opposite is likely true: the extent that people differ in arm number is likely the result of accidents and, therefore, environmental. For reasons like these, we always have to be very careful when asking nature–nurture questions, especially when we try to express the answer in terms of a single number. The heritability of a trait is not simply a property of that trait, but a property of the trait in a particular context of relevant genes and environmental factors.

Another issue with the heritability coefficient is that it divides traits’ determinants into two portions—genes and environment—which are then calculated together for the total variability. This is a little like asking how much of the experience of a symphony comes from the horns and how much from the strings; the ways instruments or genes integrate is more complex than that. It turns out to be the case that, for many traits, genetic differences affect behavior under some environmental circumstances but not others—a phenomenon called gene-environment interaction, or G x E. In one well-known example, Caspi et al. (2002) showed that among maltreated children, those who carried a particular allele of the MAOA gene showed a predisposition to violence and antisocial behavior, while those with other alleles did not. Whereas, in children who had not been maltreated, the gene had no effect. Making matters even more complicated are very recent studies of what is known as epigenetics (see module, “Epigenetics” http://noba.to/37p5cb8v), a process in which the DNA itself is modified by environmental events, and those genetic changes transmitted to children.

Some common questions about nature–nurture are, how susceptible is a trait to change, how malleable is it, and do we “have a choice” about it? These questions are much more complex than they may seem at first glance. For example, phenylketonuria is an inborn error of metabolism caused by a single gene; it prevents the body from metabolizing phenylalanine. Untreated, it causes intellectual disability and death. But it can be treated effectively by a straightforward environmental intervention: avoiding foods containing phenylalanine. Height seems like a trait firmly rooted in our nature and unchangeable, but the average height of many populations in Asia and Europe has increased significantly in the past 100 years, due to changes in diet and the alleviation of poverty. Even the most modern genetics has not provided definitive answers to nature–nurture questions. When it was first becoming possible to measure the DNA sequences of individual people, it was widely thought that we would quickly progress to finding the specific genes that account for behavioral characteristics, but that hasn’t happened. There are a few rare genes that have been found to have significant (almost always negative) effects, such as the single gene that causes Huntington’s disease, or the Apolipoprotein gene that causes early onset dementia in a small percentage of Alzheimer’s cases. Aside from these rare genes of great effect, however, the genetic impact on behavior is broken up over many genes, each with very small effects. For most behavioral traits, the effects are so small and distributed across so many genes that we have not been able to catalog them in a meaningful way. In fact, the same is true of environmental effects. We know that extreme environmental hardship causes catastrophic effects for many behavioral outcomes, but fortunately extreme environmental hardship is very rare. Within the normal range of environmental events, those responsible for differences (e.g., why some children in a suburban third-grade classroom perform better than others) are much more difficult to grasp.

The difficulties with finding clear-cut solutions to nature–nurture problems bring us back to the other great questions about our relationship with the natural world: the mind-body problem and free will. Investigations into what we mean when we say we are aware of something reveal that consciousness is not simply the product of a particular area of the brain, nor does choice turn out to be an orderly activity that we can apply to some behaviors but not others. So it is with nature and nurture: What at first may seem to be a straightforward matter, able to be indexed with a single number, becomes more and more complicated the closer we look. The many questions we can ask about the intersection among genes, environments, and human traits—how sensitive are traits to environmental change, and how common are those influential environments; are parents or culture more relevant; how sensitive are traits to differences in genes, and how much do the relevant genes vary in a particular population; does the trait involve a single gene or a great many genes; is the trait more easily described in genetic or more-complex behavioral terms?—may have different answers, and the answer to one tells us little about the answers to the others.

It is tempting to predict that the more we understand the wide-ranging effects of genetic differences on all human characteristics—especially behavioral ones—our cultural, ethical, legal, and personal ways of thinking about ourselves will have to undergo profound changes in response. Perhaps criminal proceedings will consider genetic background. Parents, presented with the genetic sequence of their children, will be faced with difficult decisions about reproduction. These hopes or fears are often exaggerated. In some ways, our thinking may need to change—for example, when we consider the meaning behind the fundamental American principle that all men are created equal. Human beings differ, and like all evolved organisms they differ genetically. The Declaration of Independence predates Darwin and Mendel, but it is hard to imagine that Jefferson—whose genius encompassed botany as well as moral philosophy—would have been alarmed to learn about the genetic diversity of organisms. One of the most important things modern genetics has taught us is that almost all human behavior is too complex to be nailed down, even from the most complete genetic information, unless we’re looking at identical twins. The science of nature and nurture has demonstrated that genetic differences among people are vital to human moral equality, freedom, and self-determination, not opposed to them. As Mordecai Kaplan said about the role of the past in Jewish theology, genetics gets a vote, not a veto, in the determination of human behavior. We should indulge our fascination with nature–nurture while resisting the temptation to oversimplify it.

Outside Resources

Web: Institute for Behavioral Genetics  http://www.colorado.edu/ibg/

Discussion Questions

• Is your personality more like one of your parents than the other? If you have a sibling, is his or her personality like yours? In your family, how did these similarities and differences develop? What do you think caused them?
• Can you think of a human characteristic for which genetic differences would play almost no role? Defend your choice.
• Do you think the time will come when we will be able to predict almost everything about someone by examining their DNA on the day they are born?
• Identical twins are more similar than fraternal twins for the trait of aggressiveness, as well as for criminal behavior. Do these facts have implications for the courtroom? If it can be shown that a violent criminal had violent parents, should it make a difference in culpability or sentencing?

Image Attributions

Figure 4.1: Sebastián Dario, https://goo.gl/OPiIWd, CC BY-NC 2.0, https://goo.gl/FIlc2e

Figure 4.2: CCO Creative Commons https://pixabay.com/en/baby-twins-brother-sister-siblings-772439/

Figure 4.3: EMSL, https://goo.gl/IRfn9g, CC BY-NC-SA 2.0, https://goo.gl/fbv27n

Figure 4.4: Paul Altobelli, https://goo.gl/SWLwm2, CC BY 2.0, https://goo.gl/9uSnqN

Figure 4.5: Sundaram Ramaswamy, https://goo.gl/Bv8lp6, CC BY 2.0, https://goo.gl/9uSnqN

Bouchard, T. J., Lykken, D. T., McGue, M., & Segal, N. L. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250(4978), 223–228.

Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A. & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854.

McGue, M., & Lykken, D. T. (1992). Genetic influence on risk of divorce. Psychological Science, 3(6), 368–373.

Plomin, R., Corley, R., DeFries, J. C., & Fulker, D. W. (1990). Individual differences in television viewing in early childhood: Nature as well as nurture. Psychological Science, 1(6), 371–377.

Plomin, R., DeFries, J. C., Knopik, V. S., & Neiderhiser, J. M. (2012). Behavioral genetics. New York, NY: Worth Publishers.

Scott, J. P., & Fuller, J. L. (1998). Genetics and the social behavior of the dog. Chicago, IL: University of Chicago Press.

Turkheimer, E. (2000). Three laws of behavior genetics and what they mean. Current Directions in Psychological Science, 9(5), 160–164.

Introduction to Psychology Copyright © 2019 by Eric Turkheimer is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Nature vs. Nurture and Epigenetics

The nature-nurture question, learning objectives.

• Understand what the nature–nurture debate is and why the problem fascinates us.
• Understand why nature–nurture questions are difficult to study empirically.
• Know the major research designs that can be used to study nature–nurture questions.
• Appreciate the complexities of nature–nurture and why questions that seem simple turn out not to have simple answers.

Introduction

There are three related problems at the intersection of philosophy and science that are fundamental to our understanding of our relationship to the natural world: the mind–body problem, the free will problem, and the nature–nurture problem. These great questions have a lot in common. Everyone, even those without much knowledge of science or philosophy, has opinions about the answers to these questions that come simply from observing the world we live in. Our feelings about our relationship with the physical and biological world often seem incomplete. We are in control of our actions in some ways, but at the mercy of our bodies in others; it feels obvious that our consciousness is some kind of creation of our physical brains, at the same time we sense that our awareness must go beyond just the physical. This incomplete knowledge of our relationship with nature leaves us fascinated and a little obsessed, like a cat that climbs into a paper bag and then out again, over and over, mystified every time by a relationship between inner and outer that it can see but can’t quite understand.

It may seem obvious that we are born with certain characteristics while others are acquired, and yet of the three great questions about humans’ relationship with the natural world, only nature–nurture gets referred to as a “debate.” In the history of psychology, no other question has caused so much controversy and offense: We are so concerned with nature–nurture because our very sense of moral character seems to depend on it. While we may admire the athletic skills of a great basketball player, we think of his height as simply a gift, a payoff in the “genetic lottery.” For the same reason, no one blames a short person for his height or someone’s congenital disability on poor decisions: To state the obvious, it’s “not their fault.” But we do praise the concert violinist (and perhaps her parents and teachers as well) for her dedication, just as we condemn cheaters, slackers, and bullies for their bad behavior.

The problem is, most human characteristics aren’t usually as clear-cut as height or instrument-mastery, affirming our nature–nurture expectations strongly one way or the other. In fact, even the great violinist might have some inborn qualities—perfect pitch, or long, nimble fingers—that support and reward her hard work. And the basketball player might have eaten a diet while growing up that promoted his genetic tendency for being tall. When we think about our own qualities, they seem under our control in some respects, yet beyond our control in others. And often the traits that don’t seem to have an obvious cause are the ones that concern us the most and are far more personally significant. What about how much we drink or worry? What about our honesty, or religiosity, or sexual orientation? They all come from that uncertain zone, neither fixed by nature nor totally under our own control.

Researchers have learned a great deal about the nature-nurture dynamic by working with animals. But of course many of the techniques used to study animals cannot be applied to people. Separating these two influences in human subjects is a greater research challenge. [Photo: mharrsch]

One major problem with answering nature-nurture questions about people is, how do you set up an experiment? In nonhuman animals, there are relatively straightforward experiments for tackling nature–nurture questions. Say, for example, you are interested in aggressiveness in dogs. You want to test for the more important determinant of aggression: being born to aggressive dogs or being raised by them. You could mate two aggressive dogs—angry Chihuahuas—together, and mate two nonaggressive dogs—happy beagles—together, then switch half the puppies from each litter between the different sets of parents to raise. You would then have puppies born to aggressive parents (the Chihuahuas) but being raised by nonaggressive parents (the Beagles), and vice versa, in litters that mirror each other in puppy distribution. The big questions are: Would the Chihuahua parents raise aggressive beagle puppies? Would the beagle parents raise non aggressive Chihuahua puppies? Would the puppies’ nature win out, regardless of who raised them? Or… would the result be a combination of nature and nurture? Much of the most significant nature–nurture research has been done in this way (Scott & Fuller, 1998), and animal breeders have been doing it successfully for thousands of years. In fact, it is fairly easy to breed animals for behavioral traits.

With people, however, we can’t assign babies to parents at random, or select parents with certain behavioral characteristics to mate, merely in the interest of science (though history does include horrific examples of such practices, in misguided attempts at “eugenics,” the shaping of human characteristics through intentional breeding). In typical human families, children’s biological parents raise them, so it is very difficult to know whether children act like their parents due to genetic (nature) or environmental (nurture) reasons. Nevertheless, despite our restrictions on setting up human-based experiments, we do see real-world examples of nature-nurture at work in the human sphere—though they only provide partial answers to our many questions.

The science of how genes and environments work together to influence behavior is called  behavioral genetics . The easiest opportunity we have to observe this is the adoption study . When children are put up for adoption, the parents who give birth to them are no longer the parents who raise them. This setup isn’t quite the same as the experiments with dogs (children aren’t assigned to random adoptive parents in order to suit the particular interests of a scientist) but adoption still tells us some interesting things, or at least confirms some basic expectations. For instance, if the biological child of tall parents were adopted into a family of short people, do you suppose the child’s growth would be affected? What about the biological child of a Spanish-speaking family adopted at birth into an English-speaking family? What language would you expect the child to speak? And what might these outcomes tell you about the difference between height and language in terms of nature-nurture?

Studies focused on twins have lead to important insights about the biological origins of many personality characteristics. [Photo: ethermoon] 

Another option for observing nature-nurture in humans involves twin studies . There are two types of twins: monozygotic (MZ) and dizygotic (DZ). Monozygotic twins, also called “identical” twins, result from a single zygote (fertilized egg) and have the same DNA. They are essentially clones. Dizygotic twins, also known as “fraternal” twins, develop from two zygotes and share 50% of their DNA. Fraternal twins are ordinary siblings who happen to have been born at the same time. To analyze nature–nurture using twins, we compare the similarity of MZ and DZ pairs. Sticking with the features of height and spoken language, let’s take a look at how nature and nurture apply: Identical twins, unsurprisingly, are almost perfectly similar for height. The heights of fraternal twins, however, are like any other sibling pairs: more similar to each other than to people from other families, but hardly identical. This contrast between twin types gives us a clue about the role genetics plays in determining height. Now consider spoken language. If one identical twin speaks Spanish at home, the co-twin with whom she is raised almost certainly does too. But the same would be true for a pair of fraternal twins raised together. In terms of spoken language, fraternal twins are just as similar as identical twins, so it appears that the genetic match of identical twins doesn’t make much difference.

Twin and adoption studies are two instances of a much broader class of methods for observing nature-nurture called quantitative genetics , the scientific discipline in which similarities among individuals are analyzed based on how biologically related they are. We can do these studies with siblings and half-siblings, cousins, twins who have been separated at birth and raised separately (Bouchard, Lykken, McGue, & Segal, 1990; such twins are very rare and play a smaller role than is commonly believed in the science of nature–nurture), or with entire extended families (see Plomin, DeFries, Knopik, & Neiderhiser, 2012, for a complete introduction to research methods relevant to nature–nurture).

For better or for worse, contentions about nature–nurture have intensified because quantitative genetics produces a number called a heritability coefficient , varying from 0 to 1, that is meant to provide a single measure of genetics’ influence of a trait. In a general way, a heritability coefficient measures how strongly differences among individuals are related to differences among their genes. But beware: Heritability coefficients, although simple to compute, are deceptively difficult to interpret. Nevertheless, numbers that provide simple answers to complicated questions tend to have a strong influence on the human imagination, and a great deal of time has been spent discussing whether the heritability of intelligence or personality or depression is equal to one number or another.

Quantitative genetics uses statistical methods to study the effects that both heredity and environment have on test subjects. These methods have provided us with the heritability coefficient which measures how strongly differences among individuals for a trait are related to differences among their genes. [Image: EMSL]

One reason nature–nurture continues to fascinate us so much is that we live in an era of great scientific discovery in genetics, comparable to the times of Copernicus, Galileo, and Newton, with regard to astronomy and physics. Every day, it seems, new discoveries are made, new possibilities proposed. When Francis Galton first started thinking about nature–nurture in the late-19th century he was very influenced by his cousin, Charles Darwin, but genetics per se was unknown. Mendel’s famous work with peas, conducted at about the same time, went undiscovered for 20 years; quantitative genetics was developed in the 1920s; DNA was discovered by Watson and Crick in the 1950s; the human genome was completely sequenced at the turn of the 21st century; and we are now on the verge of being able to obtain the specific DNA sequence of anyone at a relatively low cost. No one knows what this new genetic knowledge will mean for the study of nature–nurture, but as we will see in the next section, answers to nature–nurture questions have turned out to be far more difficult and mysterious than anyone imagined.

Outside Resources

Discussion questions.

• Is your personality more like one of your parents than the other? If you have a sibling, is his or her personality like yours? In your family, how did these similarities and differences develop? What do you think caused them?
• Can you think of a human characteristic for which genetic differences would play almost no role? Defend your choice.
• Do you think the time will come when we will be able to predict almost everything about someone by examining their DNA on the day they are born?
• Identical twins are more similar than fraternal twins for the trait of aggressiveness, as well as for criminal behavior. Do these facts have implications for the courtroom? If it can be shown that a violent criminal had violent parents, should it make a difference in culpability or sentencing?
• Bouchard, T. J., Lykken, D. T., McGue, M., & Segal, N. L. (1990). Sources of human psychological differences: The Minnesota study of twins reared apart. Science, 250(4978), 223–228.
• Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A. & Poulton, R. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851–854.
• McGue, M., & Lykken, D. T. (1992). Genetic influence on risk of divorce. Psychological Science, 3(6), 368–373.
• Plomin, R., Corley, R., DeFries, J. C., & Fulker, D. W. (1990). Individual differences in television viewing in early childhood: Nature as well as nurture. Psychological Science, 1(6), 371–377.
• Plomin, R., DeFries, J. C., Knopik, V. S., & Neiderhiser, J. M. (2012). Behavioral genetics. New York, NY: Worth Publishers.
• Scott, J. P., & Fuller, J. L. (1998). Genetics and the social behavior of the dog. Chicago, IL: University of Chicago Press.
• Turkheimer, E. (2000). Three laws of behavior genetics and what they mean. Current Directions in Psychological Science, 9(5), 160–164.
• The Nature-Nurture Question. Authored by : Eric Turkheimer. Provided by : University of Virginia. Located at : http://nobaproject.com/ . Project : Noba Project. License : CC BY-NC-SA: Attribution-NonCommercial-ShareAlike

Nature vs. Nurture

Reviewed by Psychology Today Staff

The expression “nature vs. nurture” describes the question of how much a person's characteristics are formed by either “nature” or “nurture.” “Nature” means innate biological factors (namely genetics ), while “nurture” can refer to upbringing or life experience more generally.

Traditionally, “nature vs. nurture” has been framed as a debate between those who argue for the dominance of one source of influence or the other, but contemporary experts acknowledge that both “nature” and “nurture” play a role in psychological development and interact in complex ways.

• The Meaning of Nature vs. Nurture
• The Nature-vs.-Nurture Debate
• Identifying Genetic and Environmental Factors

The wording of the phrase “nature vs. nurture” makes it seem as though human individuality— personality traits, intelligence , preferences, and other characteristics—must be based on either the genes people are born with or the environment in which they grew up. The reality, as scientists have shown, is more complicated, and both these and other factors can help account for the many ways in which individuals differ from each other.

The words “nature” and “nurture” themselves can be misleading. Today, “ genetics ” and “environment” are frequently used in their place—with one’s environment including a broader range of experiences than just the nurturing received from parents or caregivers. Further, nature and nurture (or genetics and environment) do not simply compete to influence a person, but often interact with each other; “nature and nurture” work together. Finally, individual differences do not entirely come down to a person’s genetic code or developmental environment—to some extent, they emerge due to messiness in the process of development as well.

A person’s biological nature can affect a person’s experience of the environment. For example, a person with a genetic disposition toward a particular trait, such as aggressiveness, may be more likely to have particular life experiences (including, perhaps, receiving negative reactions from parents or others). Or, a person who grows up with an inclination toward warmth and sociability may seek out and elicit more positive social responses from peers. These life experiences could, in turn, reinforce an individual’s initial tendencies. Nurture or life experience more generally may also modify the effects of nature—for example, by expanding or limiting the extent to which a naturally bright child receives encouragement, access to quality education , and opportunities for achievement.

Epigenetics—the science of modifications in how genes are expressed— illustrates the complex interplay between “nature” and “nurture.” An individual’s environment, including factors such as early-life adversity, may result in changes in the way that parts of a person’s genetic code are “read.” While these epigenetic changes do not override the important influence of genes in general, they do constitute additional ways in which that influence is filtered through “nurture” or the environment.

Theorists and researchers have long battled over whether individual traits and abilities are inborn or are instead forged by experiences after birth. The debate has had broad implications: The real or perceived sources of a person’s strengths and vulnerabilities matter for fields such as education, philosophy , psychiatry , and clinical psychology. Today’s consensus—that individual differences result from a combination of inherited and non-genetic factors—strikes a more nuanced middle path between nature- or nurture-focused extremes.

The debate about nature and nurture has roots that stretch back at least thousands of years, to Ancient Greek theorizing about the causes of personality. During the modern era, theories emphasizing the role of either learning and experience or biological nature have risen and fallen in prominence—with genetics gaining increasing acknowledgment as an important (though not exclusive) influence on individual differences in the later 20th century and beyond.

“Nature versus nurture” was used by English scientist Francis Galton. In 1874, he published the book English Men of Science: Their Nature and Nurture , arguing that inherited factors were responsible for intelligence and other characteristics.

Genetic determinism emphasizes the importance of an individual’s nature in development. It is the view that genetics is largely or totally responsible for an individual’s psychological characteristics and behavior. The term “biological determinism” is often used synonymously.

The blank slate (or “tabula rasa”) view of the mind emphasizes the importance of nurture and the environment. Notably described by English philosopher John Locke in the 1600s, it proposed that individuals are born with a mind like an unmarked chalkboard and that its contents are based on experience and learning. In the 20th century, major branches of psychology proposed a primary role for nurture and experience , rather than nature, in development, including Freudian psychoanalysis and behaviorism.

Modern scientific methods have allowed researchers to advance further in understanding the complex relationships between genetics, life experience, and psychological characteristics, including mental health conditions and personality traits. Overall, the findings of contemporary studies underscore that with some exceptions—such as rare diseases caused by mutations in a single gene—no one factor, genetic or environmental, solely determines how a characteristic develops.

Scientists use multiple approaches to estimate how important genetics are for any given trait, but one of the most influential is the twin study. While identical (or monozygotic) twins share the same genetic code, fraternal (or dizygotic) twins share about 50 percent of the same genes, like typical siblings. Scientists are able to estimate the degree to which the variation in a particular trait, like extraversion , is explained by genetics in part by analyzing how similar identical twins are on that trait, compared to fraternal twins. ( These studies do have limitations, and estimates based on one population may not closely reflect all other populations.) 

It’s hard to call either “nature” or “nurture,” genes or the environment, more important to human psychology. The impact of one set of factors or the other depends on the characteristic, with some being more strongly related to one’s genes —for instance, autism appears to be more heritable than depression . But in general, psychological traits are shaped by a balance of interacting genetic and non-genetic influences.

Both genes and environmental factors can contribute to a person developing mental illness. Research finds that a major part of the variation in the risk for psychiatric conditions such as autism spectrum disorder, anxiety disorders, depression, and schizophrenia can be attributed to genetic differences. But not all of that risk is genetic, and life experiences, such as early-life abuse or neglect, may also affect risk of mental illness (and some individuals, based on their genetics, are likely more susceptible to environmental effects than others).

Like other psychological characteristics, personality is partly heritable. Research suggests less than half of the difference between people on measures of personality traits can be attributed to genes (one recent overall estimate is 40 percent). Non-genetic factors appear to be responsible for an equal or greater portion of personality differences between individuals. Some theorize that the social roles people adopt and invest in as they mature are among the more important non-genetic factors in personality development.

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Perceptions of nature, nurture and behaviour

Mairi levitt.

Department of Politics, Philosophy and Religious Studies, Lancaster University, County South, Lancaster, LA1 4YL UK

Trying to separate out nature and nurture as explanations for behaviour, as in classic genetic studies of twins and families, is now said to be both impossible and unproductive. In practice the nature-nurture model persists as a way of framing discussion on the causes of behaviour in genetic research papers, as well as in the media and lay debate. Social and environmental theories of crime have been dominant in criminology and in public policy while biological theories have been seen as outdated and discredited. Recently, research into genetic variations associated with aggressive and antisocial behaviour has received more attention in the media. This paper explores ideas on the role of nature and nurture in violent and antisocial behaviour through interviews and open-ended questionnaires among lay publics. There was general agreement that everybody’s behaviour is influenced to varying degrees by both genetic and environmental factors but deterministic accounts of causation, except in exceptional circumstances, were rejected. Only an emphasis on nature was seen as dangerous in its consequences, for society and for individuals themselves. Whereas academic researchers approach the debate from their disciplinary perspectives which may or may not engage with practical and policy issues, the key issue for the public was what sort of explanations of behaviour will lead to the best outcomes for all concerned.

Trying to separate out nature and nurture as explanations for behaviour, as in classic genetic studies of twins and families, is now said to be both impossible and unproductive. The nature-nurture debate is declared to be officially redundant by social scientists and scientists, ‘outdated, naive and unhelpful’ (Craddock, 2011 , p.637), ‘a false dichotomy’ (Traynor 2010 , p.196). Geneticists argue that nature and nurture interact to affect behaviour through complex and not yet fully understood ways, but, in practice, the debate continues 1 . Research papers by psychologists and geneticists still use the terms nature and nurture, or genes and environment, to consider their relative influences on, for example, temperament and personality, childhood obesity and toddler sleep patterns (McCrae et al., 2000 ; Anderson et al., 2007 ; Brescianini, 2011 ). These papers separate out and quantify the relative influences of nature/genes and nurture/environment. These papers might be taken to indicate how individuals acquire their personality traits or toddlers acquire their sleep patterns; part is innate or there at birth and part is acquired after birth due to environmental influences. The findings actually refer to technical heritability which is, ‘the proportion of phenotypic variation attributable to genetic differences between individuals’ (Keller, 2010 , p.57). In practice, as Keller illustrates, there is ‘slippage’ between heritability, meaning a trait being biologically transmissible, and technical heritability. This is not simply a mistake made by the media or ‘media hype’ but is, she argues, ‘almost impossible to avoid’ (ibid, p.71).

While researchers are aware of the complexity of gene-environment interaction, the ‘nature and nurture’ model persists as a simple way of framing discussion on the causes of behaviours. It is also a site of struggle between (and within) academic disciplines and, through influence on policy, has consequences for those whose behaviours are investigated. There is general agreement between social scientists and geneticists about the past abuses of genetics but disagreement over whether it will be possible for the new behavioural genetics to avoid discrimination and eugenic practices, and about the likely benefits that society will gain from this research (Parens et al. 2006 , xxi). In a special issue of the American Journal of Sociology ‘Exploring genetics and social structure’, Bearman considers the reasons why sociologists are concerned about genetic effects on behaviour; first they see it as legitimating existing societal arrangements, which assumes that ‘genetic’ is unchangeable. Second, if sociologists draw on genetic research it contaminates the sociological enterprise and, third, whatever claims are made to the contrary, it is a eugenicist project (Bearman, 2008 , vi). As we will see all these concerns were expressed by the publics in this study. Policy makers and publics are interested in explaining problem behaviour in order to change/control it, not in respecting disciplinary boundaries, and will expect the role of genetics to be considered alongside social factors. 2

Social and environmental theories of criminal behaviour have been dominant in criminology, and in public policy (Walsh, 2009 , p.7). Genetic disorders and mental illness have provided explanations for a small minority of offenders with specific conditions. A 2007 survey of American criminologists found that ‘criminologists of all ideological persuasions view alleged biosocial causes of crime (hormonal, genetic, and evolutionary factors and possibly low intelligence) as relatively unimportant’ compared with environmental causes (Cooper et al., 2010 ). Sociology textbooks have typically discussed biological theories of criminality only as discredited (Haralambos and Holborn, 2004 , Giddens, 2009 ). Biosocial theories are seen as attractive to ‘agents of social control’ and to be more likely to lead to abusive treatment of offenders. However, with increasing research and public interest in genetics more attention has been paid to biological aspects of crime and to genetic variations within the normal range. Research has focussed on violent and antisocial behaviours which are criminal or may be seen as a precursor to criminal behaviour, for example, antisocial behaviour in young people. Media reports have headlined ‘warrior genes’, ‘the aggressive gene’ and the ‘get out of jail free gene’, all referring to levels of monoamine oxidase A (MAOA) (Lea and Chambers, 2007 ; Levitt and Pieri, 2009 ) 3 . Think tanks and ethics groups have considered the ethics and practicalities of genetic testing for behavioural traits (Campbell and Ross, 2004 ; Dixon, 2005 Nuffield Council on Bioethics, 2002 ).

An attraction of research into genes and behaviour is the hope that identifying a genetic factor that is correlated with an increased incidence of, say, violent and antisocial behaviour, will point to a way of reducing such behaviour. Fotaki discusses the attraction of biological explanations of inequalities in health based on the assumption that genetic interventions ‘would succeed in addressing the causes of ill health that public health policies cannot.’ (Fotaki, 2011 , p.641). The danger is that biological explanations ‘are once more employed for political purposes to explain away the social roots of health inequalities.’ (ibid). Social scientists, and criminologists, have presented biological/genetic explanations of behaviour as dangerous in terms of their potential effect on the individuals or groups identified as genetically at risk. There are obvious dangers of discrimination against, and the stigmatisation of, already vulnerable groups who would be the first to be tested i.e. ‘problem’ families or minority ethnic groups. Discrimination could affect education, employment and family life. The effect of an individual being told s/he has a risk based on a genetic test has been much discussed in relation to health risks (Claassen et al., 2010 . While such information could be motivating, because it is personalised, it can also induce a fatalistic attitude that discourages the person from taking preventative measures. Claasen et al. conclude that it is important to identify those vulnerable to the fatalistic impact and to tailor health risk information (ibid p.194). Identifying risk for behaviour, rather than for disease, is likely to be more problematic because of the difficulty of finding preventative measures that are within the individuals’ own control.

..using DNA to assess risk, make a diagnosis or tailor treatments, may weaken beliefs in the efficacy of preventive behaviour and reinforce biological ways of reducing risk, resulting in a preference for medication as opposed to behavioural means to control or reduce risk (ibid, xiv).

Claasen et al.’s comment on genetic tests for health conditions could apply equally to parents given a behavioural risk for their young child from a genetic test, perhaps before any problem behaviour was evident. The test result could weaken parents’ belief that they could take action to prevent/reduce the risk of the behaviour developing in their child and pharmaceutical solutions, as posited by Caspi et al. might not be available (Caspi et al., 2002 , xvii). However, it is not necessarily the case that evidence of genetic or biological influence on behaviour leads to more punitive treatment. DeLisi et al. give the example of the use of findings from adolescent brain science in the case of Roper v. Simmons in the US which abolished the death penalty for adolescents. On the basis of the research it was stated that young people under the age of 18 ‘are more vulnerable or susceptible to negative influences and outside pressures including peer pressure’ (DeLisa et al., 2010 , p.25) When evidence on genetic traits associated with criminal behaviour has been allowed by courts, mainly in the US, it has so far more often been accepted as a mitigating rather than an aggravating factor in the offenders’ behaviour (Denno, 2009 , Farahany and Coleman, 2006 ).

Environmental explanations of behaviour can, of course, also be presented as deterministic, claiming a closed future for those experiencing poverty and disadvantage. However, it is biological explanations that have caused more concern not only because of the history of eugenics but also because they may be seen as more fundamental, being there from birth, and as harder to change. The public in surveys are reported to see the greatest role for genetic factors in physical features, a lesser role in health conditions and a smaller role still in human behaviour (Condit, 2010 , p.619).

Public perceptions

The model of nature/genes and nurture/environment is still used in behavioural genetics, as well as in popular culture, and has implications for public policy, including the treatment of offenders who claim that a genetic trait has influenced their criminal behaviour. The aim of this research was to explore ideas on the causes of behaviour, particularly violent and antisocial behaviour and examine how respondents use the nature/nurture model. This qualitative research looks at the ways in which lay publics in different age groups conceptualise the factors and influences that made them who they are and their explanations for the behaviour of other people; especially violent behaviour. It was hypothesised that the increased research and media emphasis on the role of genetic factors in health and behaviour might result in an increasing interest in ‘nature’, biology and genes as explanations for behaviour particularly among the young, but, when explaining their own behaviour people might prefer to see themselves as agents with control over their lives. By exploring explanations of behaviour with respondents from different generations, age differences should be apparent.

The views of 78 respondents from 3 generations were gathered by individual interview and questionnaires, using the same open ended questions and responses to two real-life criminal court case studies where environmental or genetic factors had been used by the defence team. Respondents were drawn from a group of retired people participating in an informal ‘senior learners’ programme at Lancaster University, a group of their mainly younger relatives and, in order to recruit more third generation respondents, a group of first year students taking a criminology module. The senior learners group had a programme of talks and discussions and could attend undergraduate lectures. They had, by definition, shown an interest in current issues in a range of fields. There were no educational or age requirements for the group but all the volunteers were retired from paid work and were aged from around 65 years to over 80 years.. They had had similar careers to those popular with social science students; social work, probation, teaching and administrative positions. The senior learners were asked to pass on questionnaires to younger relatives to investigate age differences in attitudes. The first 13 senior learners who responded were interviewed but as only 15 questionnaires were received from their relatives ethical approval was obtained to distribute the same questionnaire to Lancaster University students taking the criminology first year module. Most students were enrolled on social science degrees, including psychology and sociology, and age 18 or 19. While the sample of senior learners and relatives had only a few more women than men, 78 per cent of the students were female reflecting the gender balance on the module as a whole. This makes it difficult to comment on any gender differences in responses. No claims to generalisability are made for this exploratory study. Responses were coded and entered on SPSS and also analysed thematically using Atlas-ti.

The introduction to the interviews and questionnaire was ‘I am interested in your views and ideas on what makes us the people we are; what makes people behave the way they do? What is the influence of nature and nurture?’ The terms, nature and nurture were not used again until the final question. Although the terms were not defined all respondents readily used them with consistent meanings. They identified ‘nature’ with biology, ‘what you are born with’ and genes or DNA and nurture with all aspects of the environment including parenting, socio-economic conditions, the food you eat, culture and other people. Their understanding of environment was therefore similar to that used by genetic researchers; environment as everything that is external to the individual, although they tended to refer more to the social than the biological environment.

A general warm-up question asked whether, in their own family, there was anything they thought of as a ‘family trait’. Then respondents were asked; ‘Imagine a baby swapped at birth and brought up in a completely different family– which influences do you think would be most important – the influence of the birth parents or the influences of the new family- and why?’ 4 The rest of the interview schedule, and the subsequent questionnaire, consisted of open-ended questions.

Respondents were asked how they would explain different kinds of behaviour if they came across a child who is kind and considerate; a young person who displays antisocial and aggressive behaviour adult and an adult with criminal convictions for violence. This was to tap into any differences in general explanations of good and bad behaviour in young people and adults. A quotation about the child killers in the Bulger case being ‘unreformable’ was used to ascertain whether they saw some types of violent behavior, and the actors concerned, as immutable. In order to see how respondents conceptualized the influences of nature/biology/genes and environment/people/experiences in their own lives, respondents were asked to write down ‘what or who made you what you are today’ and any explanation of their responses. Comments were gathered on the introduction of an environmental factor (childhood neglect) by the defence in a violent attack by two young boys in England, and on a genetic factor (MAOA levels) introduced by the defence in an criminal court in Italy. Respondents were asked how they thought such evidence should be dealt with; whether it should affect the degree of blame and whether it should affect criminal responsibility. The final question asked if it mattered ‘for individuals or society’ whether nature or nurture was seen as most important in explaining problem behaviour. Those interviewed were asked if they had any further comments and there was a space for any additional comments on the questionnaire.

This paper focuses on the ways in which respondents employed nature/genes and nurture/environment in their responses as a whole and what other concepts they drew on when explaining behaviour.

Respondents’ explanations of what makes people behave the way they do are discussed through three themes.

• Nurture is more influential than nature
• Nature and nurture interact
• Emphasising nature (but never nurture) can be dangerous

Theme 1: Nurture is more influential than nature

Whether asked about influences on a baby adopted at birth, on their own lives, on an aggressive child or a violent young person, almost all respondents emphasised nurture. Parents and family were seen as the most important influences for babies and young children, moving to peer group and other relationships and experiences for a young person. The explanation for the violent behaviour of an adult had more to do with the individual and the importance of nurture/environment in explaining behaviour weakened. The quotations below explaining behaviour in a child adopted at birth, a young person and an adult illustrate the widening of influences from infancy through childhood and the onus on adults to take responsibility for themselves.

[a child] The environment in which a child grows up in, particularly the influence and role of the parents shapes how a child will grow up and what sort of adult they will be (77 Student). [a young person] I believe that upbringing shapes a person’s personality. Provisions of education, lifestyle opportunities and friendship groups all determine ….outlook. You can see evidence in young people at the school I teach at (20 Relative). Once adult they have to take responsibility for themselves and address whatever has been in their background. An adult can’t turn round and say it’s not my fault (5 Senior Learner).

Participants also saw themselves as shaped by the people surrounding them, starting with their parents, or those who brought them up. Several mentioned the illness and/or death of a parent during their childhood and older respondents talked about separation due to the second world war. Students were especially likely to mention the influence of morals instilled in them by their parents, the core values and discipline that they were taught at home. Educational experiences were important to all. For the senior learners the school leaving age had been age 15, so whether or not they stayed on at school and took public examinations was crucial for their future, and, this decision depended largely on their parents and environment. For the student respondents who had come to university from school, life so far has been ‘kind of set-out’ (41 Student), in the sense that they had progressed through the education system to gain qualifications for university. For their peer group it was normal still to be in education or training at the age of 18.

The lasting effects of early influences were particularly striking among the senior learners, because they were much further removed in years from their childhood. Many related stories about parental influence and also about teachers who taught them at least 50 years ago and had affected them for better or worse. For example a senior learner recalled one of her teachers;

I hated primary school – the teacher in 3rd or 4th year juniors [for ages 9–11] I hated her she was not a nice woman….. I passed to go to the grammar school and it shocked her. She made a derogatory comment – may not have been directed at me but felt it was- about some who should have passed and didn’t and some passing who should not have done…… I always vowed I would never be like that when I was teaching….(11 Senior Learner).

Those who related negative influences presented themselves as active in response, not necessarily at the time but later in their lives. For example a student whose mother had died wrote that ‘it made me more independent’ and another student who was bullied at school wrote that ‘it made me stronger’. The adult had to deal with all the influences (negative or positive) and take control.

Theme 2: Nature and nurture interact

While respondents’ view of themselves and of a child adopted at birth assigned greater influence to environment this did not mean that they held a simplistic model of, for example 60:40 nurture to nature. In this one question when they were asked to choose one or other as the major influence, almost all chose nurture, as many social scientists might do. However, in open questions and comments more complex interactive models were expressed. Environment/nurture can affect genes/nature and vice versa. No one used the term epigenetics but responses referred to the possibility of environmental influences affecting gene expression, for example;

People with certain predispositions (e.g. to violence) are affected by society, and society affects how their genes are expressed (40 Student).

An older respondent reflects on personal experience of child rearing and asks whether nurture is influenced by nature;

I think the nature nurture debate is very interesting. In my family I can see where my children have their own natures that have developed despite being brought up in the same family with the same boundaries etc. However, as a parent did I alter how I nurture them to take into account their nature? (14 Senior Learner).

This quotation illustrates the inseparability of nature and nurture. The child is developing within the family and the parent is developing parenting strategies informed by previous experiences and by other influences including the reactions of the children.

It was obvious to respondents that both genetic and environmental factors impact on everyone (although the role of genes is not yet understood) and it will be harder for some than for others to behave well because of their genes and environment. These people may need different treatment or extra help if they have committed violent and aggressive crimes but that does not excuse their behaviour. Only in exceptional cases, like insanity, can a young person or adult be said to have no choice but to act in a particular way. It is important that people are seen as responsible while also giving them the help they need. In these two comments the treatment for environmental problems and ‘biology’ are similar; the individual can be helped to modify his/her behaviour.

No, [nature and nurture] both play a part, but they can’t be the explanation for everything. Some people grow up in broken homes and get treated appallingly- yet they seem to understand right + wrong and accept responsibility for their actions. There are too many excuses and we never solve any problems, just make them harder to resolve.......I think if you are sane and you know right from wrong you need to suffer the consequences if you’ve committed a crime, but I do appreciate you may need help psychologically if you have anger issues, for example. If we constantly find reasons to diminish blame from people who have committed heinous acts of crime more people will think they can get away with it and it will cause more harm than good (78 Student). Some say you can’t fight your biology, but there are social factors that can stop bad behaviour like learned restraint (72 Student).

The desire to leave a space for individual agency may be linked to the finding that emphasising nature, but never nurture, could be dangerous. It is clear that as children grow up they can exercise more control over their environment, although some have more control and choices than others. On the other hand, whatever the individual is born with (genes and nature) is, or seems to be, less malleable which could lead to different criminal justice policies and different social perceptions of the criminal.

Theme 3: Emphasising nature (but never nurture) can be dangerous for society as a whole as well as for the criminal and victims

The question asked was whether it mattered ‘for individuals or society’ if either nature or nurture was seen as most important in explaining problem behavior. The two most popular answers were that both nature and nurture were needed to explain behaviour, or, that nurture was more important and that there were dangers in emphasising nature. No one in the sample regarded an emphasis on nurture as dangerous or detrimental to the individual or society. On the contrary, emphasising nurture was thought more likely to lead to non-punitive treatment of offenders. There would be attempts to alter future behaviour through improved education and parenting and spreading of knowledge in society about the impact nurture has on young people. Society as a whole would share the blame rather than the individual. As a student put it; ‘society as a whole [would be] open for criticism’ (55 S). An emphasis on nurture was therefore seen as more likely to lead to understanding of problem behaviours and effective treatment, however, the individuals were still to be held responsible for their behaviour.

In contrast there was a mistrust of nature/genetic explanations that again centred on the practical consequences for individuals. It would affect the way criminals were treated by others but could also change their view of themselves. Behaviour would be seen as unchangeable, out of the control of the individual or social action. As a consequence, individual accountability might be removed. The idea that individuals must normally be held responsible for their actions was constantly emphasised (Levitt, 2013 ).

It does [matter] because [if nurture is emphasised] people will care, parent and look after and raise people with more care. However if it’s proven it is nature, then people may lose the will to live (60 Student).

Several SLs referred to the examination at the end of primary education (the ‘eleven plus’) when explaining why they emphasised environment/nurture rather than nature, or, in this case, innate intelligence. The ‘eleven plus’ examination was used to decide which children would be offered a place at an academically selective grammar school and was based on the idea that intelligence, and future academic achievement, could be accurately measured and predicted at the age of 10 or 11.

‘The 11+ was a nature thing. I did the 11+ − it had an effect. Saying children not going to improve or change. Very embedded in the whole idea of nature – it can’t really be true’ (8 Senior Learner).

An emphasis on nature has practical detrimental consequences for individuals. Their status is fixed, for example as ‘not academic’ or ‘born evil’ and suggests, to them and to others, that their ‘nature’ is unchangeable or very difficult to change by individual or social action.

Yes, [it matters] hugely as position of blame is dependent on whether a person chose to do what they did .....nature suggests no control (35 Student).

Those who thought an emphasis on nature meant people were irredeemable either gave that as a reason not to emphasise nature or to suggest that in fact ‘defects’ of nature could be overcome, as in this comment by a student emphasising the power of education;

Yes it is very important because it helps to understand if people are reformable (nurture) or irredeemable (nature). I believe we are determined by our education and thus with the proper help we can change. In the case of people with major biological defects, education is still a way to get over these obstacles and society should be ready to help these people (38 Student).

It might be thought that offenders themselves would embrace a genetic explanation of their behaviour if this was interpreted, as the respondents feared, as meaning they were not responsible for their crimes. However, a small study of juvenile offenders in the Netherlands found that they gave social explanations of their crimes and most rejected the idea that biology might be a factor. They committed a crime for a specific purpose like to get money or to impress others or they gave environmental reasons such as a deprived background or peer pressure or explained their offences were due to psychological conditions brought on by the use of alcohol and soft drugs (Horstkötter et al., 2012 , p.291). Whether they gave goal directed or environmental reasons ‘most of them also state that they had a choice and that it was their choice to commit the crime’ (ibid p.292). As one young offender said in interview;

In the end the person makes the choice himself… The choices I have made also had a share in my past. But in the end I am the one who has made these choices (ibid).

Genes and environment

Respondents were at ease with the language of nature and nurture which was only used in the introduction to the questionnaire or interview. They readily equated genes with nature and nurture with all sorts of environmental influences. There was an acknowledgement that our understanding of environmental factors is greater than our understanding of genetics but that that would change. Older respondents were more likely to be concerned about such a change.

They're going to be doing a lot more with genetics. Influences policy profoundly and people have to be very careful. It worries me that seen to be [more determining]. The complexities don’t get looked at. If you emphasise environment it is safer from a policy point of view because given that most people don’t know what they are talking about it is safer to see the person as redeemable than to come down on the side of genetics and write people off (3 Senior Learner).

This quotation is typical in its view that nature/genes are seen as determining even though the influences on behaviour are, in reality, complex. Like the studies quoted at the beginning of the article respondents often acknowledged the complexities as nature and nurture interact but separated them when explaining the causes of specific behaviours. Students were less likely to be fearful of genetic explanations of behaviour despite their academic interest in social science. However, the hypothesis that young people might be more likely to be interested in genetic explanations for behaviour was not shown in this small study. The senior learners were more likely to refer to reading on genes and display knowledge of genetics. Older respondents and their relatives more often echoed the sociologists’ concerns about behavioural genetics discussed by Bearman earlier (Bearman, 2008 ). For those who feared the practical consequences of genetic explanations, like the respondent quoted above, ‘it is safer’ to keep away from them.

Some respondents in all age groups were prepared for advances in genetics to change their understanding of behaviour and prepared for current views of genes/nature as more basic, fixed and unchanging to change too. One of the youngest relatives, in her 20s, emphasised our incomplete knowledge of genetic influences on behaviour as a reason for focussing on nurture ‘at present’;

It is very tricky as we cannot see genes and I am not sure that I totally trust the idea of blaming genes for violent behaviour- maybe the person has a gene for passive behaviour as well. …….In any case we can change nurture but at present we cannot change nature so let’s do one thing at a time (20 Relative).

As respondents in this small study grappled with explanations for their own and others’ behaviour they focussed on the practical consequences leading to a greater concern over explanations based on nature than the more familiar ones based on a complex web of environmental factors. Whereas academic researchers approach the debate from their disciplinary perspectives which may or may not engage with practical and policy issues, the key issue for the public was what sort of explanations of behaviour will lead to the best outcomes for all concerned.

1 Behavioural epigenetic research has indicated that life experiences can affect gene expression. While controversial the research suggests the possibility of further complications for the nature-nurture relationship as nurture may be said to shape nature (Buchen, 2010 Powledge, 2011 ). 2 Bearman op cit iv. The ESRC Cambridge Network Social Contexts of Pathways into Crime (SCoPiC) promoted multidisciplinary research into the causes of crime and included the E risk longitudinal twin study led by Terri Moffitt which investigated how genetic and environmental factors shape children's disruptive behaviour http://www.scopic.ac.uk Accessed 3 Sep 2013. 3 Violent and antisocial behaviour in this longitudinal study was correlated with a common genetic trait (low expression of MAOA) only where the person was severely maltreated in childhood. Behaviour was measured on 4 outcomes; diagnoses of conduct disorder, psychological tests of aggression and anti-social personality disorder and convictions for violent crime. Caspi et al. 2002 (supplementary material). 4 This initial warm-up question implied that the influences of nature and nurture could be separated and quantified as in common usage both in academic and popular discourses. As discussed respondents were able to express their views more fully (and with more complexity) in the subsequent open questions.

Acknowledgement

The support of the Economic and Social Research Council (ESRC) is gratefully acknowledged. This work was part of the Research Programme of the ESRC Genomics Network at Cesagen (ESRC Centre for Economic and Social Aspects of Genomics).

Competing interests

The author declares that she has no competing interests.

• Anderson P, Butcher KF, Schanzenbach DW. Childhood obesity and disadvantage: is nature trumping nurture? NBER working paper No. 13479. Cambridge MA: National Bureau of Economic Research; 2007. [ Google Scholar ]
• Bearman P. Exploring genetics and social structure. American Journal of Sociology. 2008; 114 (Suppl;S1):v–x. doi: 10.1086/596596. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Brescianini S, Volzone A, Fagnani C, Patriarca V, Grimaldi V, Lanni R, Serino L, Mastroiacovo P, Stazi MA. Genetic and environmental factors shape infant sleep patterns: a study of 18-month-old twins. Pediatrics. 2011; 127 (5):1296–1302. doi: 10.1542/peds.2010-0858. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Buchen L. In their nurture – can epigenetics underlie the enduring effects for a mother’s love. Nature. 2010; 467 :146–148. doi: 10.1038/467146a. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Campbell E, Ross LF. Attitudes of healthcare professionals and parents regarding genetic testing for violent traits in childhood. Journal of Medical Ethics. 2004; 30 :580–586. doi: 10.1136/jme.2003.005389. [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Caspi A, et al. Role of genotype in the cycle of violence in maltreated children. Science. 2002; 2 (5582):851–854. doi: 10.1126/science.1072290. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Claassen L, Henneman L, De Vet R, Knol D, Marteau T, Timmermans D. Fatalistic responses to different types of genetic risk information: Exploring the role of Self-Malleability. Psychology and Health. 2010; 25 (2):183–196. doi: 10.1080/08870440802460434. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Condit CM. When do people deploy genetic determinism? A review pointing to te need for multi-Factorial theories of public utilization of scientific discourses. Sociology Compass. 2010; 5 (7):618–635. doi: 10.1111/j.1751-9020.2011.00385.x. [ CrossRef ] [ Google Scholar ]
• Cooper JA, Walsh A, Ellis L. Is criminology moving toward a paradigm shift? Evidence from a Survey of the American Society of Criminology Journal of Criminal Justice Education. 2010; 21 (3):332–347. [ Google Scholar ]
• Craddock N. Horses for courses: the need for pragmatism and realism as well as balance and caution. A commentary on Angel. Social Science and Medicine. 2011; 73 :636–638. doi: 10.1016/j.socscimed.2011.06.049. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• DeLisa M, Wright JP, Vaughn MG, Beaver KM. Nature and nurture by definition means both: a response to males. Journal of Adolescent Research. 2010; 25 (1):24–30. doi: 10.1177/0743558409353063. [ CrossRef ] [ Google Scholar ]
• Denno DW. Behavioral genetics evidence in criminal cases: 1994–2007. In: Farahany NA, editor. The impact of behavioral sciences on criminal law. Oxford: Oxford University Press; 2009. pp. 317–354. [ Google Scholar ]
• Dixon M. Brave new choices: behavioural genetics and public policy. London: IPPR; 2005. [ Google Scholar ]
• Farahany NA, Coleman JE., Jr Genetics and responsibility: to know the criminal from the Crime. Law and Contemporary Problems. 2006; 69 :115–162. [ Google Scholar ]
• Fotaki M. Agency versus structure or nature versus nurture: when the new twist on an old debate is not that new after all: a commentary on Angel. Social Science & Medicine. 2011; 73 (5):639–642. doi: 10.1016/j.socscimed.2011.06.044. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Giddens A. Sociology. Cambridge: Polity Press; 2009. [ Google Scholar ]
• Haralambos M, Holborn M. Sociology themes and perspectives. London: Collins Educational; 2004. [ Google Scholar ]
• Horstkötter D, Berghmans R, de Ruiter C, Krumeich A, de Wert G. “We are also normal human beings, you know”. Views and attitudes of juvenile delinquents on antisocial behaviour, neurobiology and prevention. International Journal of Law and Psychiatry. 2012; 35 :289–297. doi: 10.1016/j.ijlp.2012.04.006. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Keller EF. The mirage of a space between nature and nurture. Durham & London: Duke University Press; 2010. [ Google Scholar ]
• Lea R, Chambers G. Monamine oxidase, addiction and the ‘warrior’ gene hypothesis. The New Zealand Medical Journal. 2007; 120 :1250. [ PubMed ] [ Google Scholar ]
• Levitt M. Genes, environment and responsibility for violent behaviour: ‘Whatever genes one has it is preferable that you are prevented from going around stabbing people’ New Genetics and Society. 2013; 32 (1):4–17. doi: 10.1080/14636778.2012.699352. [ CrossRef ] [ Google Scholar ]
• Levitt M, Pieri E. “It could just be an additional test couldn’t it?” Genetic testing for susceptibility to aggression and violence. New Genetics and Society. 2009; 28 (2):189–200. doi: 10.1080/14636770902901629. [ CrossRef ] [ Google Scholar ]
• McCrae RR, Costa PT, Jr, Ostendorf F, Angleitner A, Hřebíčková M, Avia MD, Sanz J, Sánchez-Bernardos ML, Kusdil ME, Woodfield R, Saunders PR, Smith PB. Nature over nurture: temperament, personality and life span development. Journal of Personality and Social Psychology. 2000; 78 (1):173–86. doi: 10.1037/0022-3514.78.1.173. [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Nuffield Council on Bioethics . Genetics and human behaviour: the ethical context. London: Nuffield Council on Bioethics; 2002. [ Google Scholar ]
• Parens E, Chapman ER, N. Press N, editors. Wrestling with behavioural genetics. Science, ethics and public conversation. Baltimore: The John Hopkins Press; 2006. [ Google Scholar ]
• Powledge TM. Behavioral Epigenetics: How nurture shapes nature. Biosciences. 2011; 61 :588–592. doi: 10.1525/bio.2011.61.8.4. [ CrossRef ] [ Google Scholar ]
• Traynor BJ, Singleton AB. Nature versus nurture: death of a dogma, and the road ahead. Neuron. 2010; 68 :196–200. doi: 10.1016/j.neuron.2010.10.002. [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
• Walsh A. Biology and criminality. The biosocial synthesis. Oxon: Routledge; 2009. [ Google Scholar ]

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What Are Nature vs. Nurture Examples?

How is nature defined, how is nurture defined, the nature vs. nurture debate, nature vs. nurture examples, what is empiricism (extreme nurture position), contemporary views of nature vs. nurture.

Nature vs. nurture is an age-old debate about whether genetics (nature) plays a bigger role in determining a person's characteristics than lived experience and environmental factors (nurture). The term "nature vs. nature" was coined by English naturalist Charles Darwin's younger half-cousin, anthropologist Francis Galton, around 1875.

In psychology, the extreme nature position (nativism) proposes that intelligence and personality traits are inherited and determined only by genetics.

On the opposite end of the spectrum, the extreme nurture position (empiricism) asserts that the mind is a blank slate at birth; external factors like education and upbringing determine who someone becomes in adulthood and how their mind works. Both of these extreme positions have shortcomings and are antiquated.

This article explores the difference between nature and nurture. It gives nature vs. nurture examples and explains why outdated views of nativism and empiricism don't jibe with contemporary views. 

Thanasis Zovoilis / Getty Images

In the context of nature vs. nurture, "nature" refers to genetics and heritable factors that are passed down to children from their biological parents.

Genes and hereditary factors determine many aspects of someone’s physical appearance and other individual characteristics, such as a genetically inherited predisposition for certain personality traits.

Scientists estimate that 20% to 60% percent of temperament is determined by genetics and that many (possibly thousands) of common gene variations combine to influence individual characteristics of temperament.

However, the impact of gene-environment (or nature-nurture) interactions on someone's traits is interwoven. Environmental factors also play a role in temperament by influencing gene activity. For example, in children raised in an adverse environment (such as child abuse or violence), genes that increase the risk of impulsive temperamental characteristics may be activated (turned on).

Trying to measure "nature vs. nurture" scientifically is challenging. It's impossible to know precisely where the influence of genes and environment begin or end.

How Are Inherited Traits Measured?

“Heritability”   describes the influence that genes have on human characteristics and traits. It's measured on a scale of 0.0 to 1.0. Very strong heritable traits like someone's eye color are ranked a 1.0.

Traits that have nothing to do with genetics, like speaking with a regional accent ranks a zero. Most human characteristics score between a 0.30 and 0.60 on the heritability scale, which reflects a blend of genetics (nature) and environmental (nurture) factors.

Thousands of years ago, ancient Greek philosophers like Plato believed that "innate knowledge" is present in our minds at birth. Every parent knows that babies are born with innate characteristics. Anecdotally, it may seem like a kid's "Big 5" personality traits (agreeableness, conscientiousness, extraversion, neuroticism, and openness) were predetermined before birth.

What is the "Big 5" personality traits

The Big 5 personality traits is a theory that describes the five basic dimensions of personality. It was developed in 1949 by D. W. Fiske and later expanded upon by other researchers and is used as a framework to study people's behavior.

From a "nature" perspective, the fact that every child has innate traits at birth supports Plato's philosophical ideas about innatism. However, personality isn't set in stone. Environmental "nurture" factors can change someone's predominant personality traits over time. For example, exposure to the chemical lead during childhood may alter personality.

In 2014, a meta-analysis of genetic and environmental influences on personality development across the human lifespan found that people change with age. Personality traits are relatively stable during early childhood but often change dramatically during adolescence and young adulthood.

It's impossible to know exactly how much "nurture" changes personality as people get older. In 2019, a study of how stable personality traits are from age 16 to 66 found that people's Big 5 traits are both stable and malleable (able to be molded). During the 50-year span from high school to retirement, some traits like agreeableness and conscientiousness tend to increase, while others appear to be set in stone.

Nurture refers to all of the external or environmental factors that affect human development such as how someone is raised, socioeconomic status, early childhood experiences, education, and daily habits.

Although the word "nurture" may conjure up images of babies and young children being cared for by loving parents, environmental factors and life experiences have an impact on our psychological and physical well-being across the human life span. In adulthood, "nurturing" oneself by making healthy lifestyle choices can offset certain genetic predispositions.

For example, a May 2022 study found that people with a high genetic risk of developing the brain disorder Alzheimer's disease can lower their odds of developing dementia (a group of symptoms that affect memory, thinking, and social abilities enough to affect daily life) by adopting these seven healthy habits in midlife:

• Staying active
• Healthy eating
• Losing weight
• Not smoking
• Reducing blood sugar
• Controlling cholesterol
• Maintaining healthy blood pressure

The nature vs. nurture debate centers around whether individual differences in behavioral traits and personality are caused primarily by nature or nurture. Early philosophers believed the genetic traits passed from parents to their children influence individual differences and traits. Other well-known philosophers believed the mind begins as a blank slate and that everything we are is determined by our experiences.

While early theories favored one factor over the other, experts today recognize there is a complex interaction between genetics and the environment and that both nature and nurture play a critical role in shaping who we are.

Eye color and skin pigmentation are examples of "nature" because they are present at birth and determined by inherited genes. Developmental delays due to toxins (such as exposure to lead as a child or exposure to drugs in utero) are examples of "nurture" because the environment can negatively impact learning and intelligence.

In Child Development

The nature vs. nurture debate in child development is apparent when studying language development. Nature theorists believe genetics plays a significant role in language development and that children are born with an instinctive ability that allows them to both learn and produce language.

Nurture theorists would argue that language develops by listening and imitating adults and other children.

In addition, nurture theorists believe people learn by observing the behavior of others. For example, contemporary psychologist Albert Bandura's social learning theory suggests that aggression is learned through observation and imitation.

In Psychology

In psychology, the nature vs. nurture beliefs vary depending on the branch of psychology.

• Biopsychology:  Researchers analyze how the brain, neurotransmitters, and other aspects of our biology influence our behaviors, thoughts, and feelings. emphasizing the role of nature.
• Social psychology: Researchers study how external factors such as peer pressure and social media influence behaviors, emphasizing the importance of nurture.
• Behaviorism: This theory of learning is based on the idea that our actions are shaped by our interactions with our environment.

In Personality Development

Whether nature or nurture plays a bigger role in personality development depends on different personality development theories.

• Behavioral theories: Our personality is a result of the interactions we have with our environment, such as parenting styles, cultural influences, and life experiences.
• Biological theories: Personality is mostly inherited which is demonstrated by a study in the 1990s that concluded identical twins reared apart tend to have more similar personalities than fraternal twins.
• Psychodynamic theories: Personality development involves both genetic predispositions and environmental factors and their interaction is complex.

In Mental Illness

Both nature and nurture can contribute to mental illness development.

For example, at least five mental health disorders are associated with some type of genetic component ( autism ,  attention-deficit hyperactivity disorder (ADHD) ,  bipolar disorder , major depression, and  schizophrenia ).

Other explanations for mental illness are environmental, such as:

• Being exposed to drugs or alcohol in utero 
• Witnessing a traumatic event, leading to post-traumatic stress disorder (PTSD)
• Adverse life events and chronic stress during childhood

In Mental Health Therapy

Mental health treatment can involve both nature and nurture. For example, a therapist may explore life experiences that may have contributed to mental illness development (nurture) as well as family history of mental illness (nature).

At the same time, research indicates that a person's genetic makeup may impact how their body responds to antidepressants. Taking this into consideration is important for finding the right treatment for each individual.

 What Is Nativism (Extreme Nature Position)?

Innatism emphasizes nature's role in shaping our minds and personality traits before birth. Nativism takes this one step further and proposes that all of people's mental and physical characteristics are inherited and predetermined at birth.

In its extreme form, concepts of nativism gave way to the early 20th century's racially-biased eugenics movement. Thankfully, "selective breeding," which is the idea that only certain people should reproduce in order to create chosen characteristics in offspring, and eugenics, arranged breeding, lost momentum during World War II. At that time, the Nazis' ethnic cleansing (killing people based on their ethnic or religious associations) atrocities were exposed.

Philosopher John Locke's tabula rasa theory from 1689 directly opposes the idea that we are born with innate knowledge. "Tabula rasa" means "blank slate" and implies that our minds do not have innate knowledge at birth.

Locke was an empiricist who believed that all the knowledge we gain in life comes from sensory experiences (using their senses to understand the world), education, and day-to-day encounters after being born.

Today, looking at nature vs. nature in black-and-white terms is considered a misguided dichotomy (two-part system). There are so many shades of gray where nature and nurture overlap. It's impossible to tease out how inherited traits and learned behaviors shape someone's unique characteristics or influence how their mind works.

The influences of nature and nurture in psychology are impossible to unravel. For example, imagine someone growing up in a household with an alcoholic parent who has frequent rage attacks. If that child goes on to develop a substance use disorder and has trouble with emotion regulation in adulthood, it's impossible to know precisely how much genetics (nature) or adverse childhood experiences (nurture) affected that individual's personality traits or issues with alcoholism.

Epigenetics Blurs the Line Between Nature and Nurture

"Epigenetics " means "on top of" genetics. It refers to external factors and experiences that turn genes "on" or "off." Epigenetic mechanisms alter DNA's physical structure in utero (in the womb) and across the human lifespan.

Epigenetics blurs the line between nature and nurture because it says that even after birth, our genetic material isn't set in stone; environmental factors can modify genes during one's lifetime. For example, cannabis exposure during critical windows of development can increase someone's risk of neuropsychiatric disease via epigenetic mechanisms.

Nature vs. nurture is a framework used to examine how genetics (nature) and environmental factors (nurture) influence human development and personality traits.

However, nature vs. nurture isn't a black-and-white issue; there are many shades of gray where the influence of nature and nurture overlap. It's impossible to disentangle how nature and nurture overlap; they are inextricably intertwined. In most cases, nature and nurture combine to make us who we are. 

Waller JC. Commentary: the birth of the twin study--a commentary on francis galton’s “the history of twins.”   International Journal of Epidemiology . 2012;41(4):913-917. doi:10.1093/ije/dys100

The New York Times. " Major Personality Study Finds That Traits Are Mostly Inherited ."

Medline Plus. Is temperament determined by genetics?

Feldman MW, Ramachandran S. Missing compared to what? Revisiting heritability, genes and culture .  Phil Trans R Soc B . 2018;373(1743):20170064. doi:10.1098/rstb.2017.0064

Winch C. Innatism, concept formation, concept mastery and formal education: innatism, concept formation and formal education .  Journal of Philosophy of Education . 2015;49(4):539-556. doi:10.1111/1467-9752.12121

Briley DA, Tucker-Drob EM. Genetic and environmental continuity in personality development: A meta-analysis .  Psychological Bulletin . 2014;140(5):1303-1331. doi:10.1037/a0037091

Damian RI, Spengler M, Sutu A, Roberts BW. Sixteen going on sixty-six: A longitudinal study of personality stability and change across 50 years .  Journal of Personality and Social Psychology . 2019;117(3):674-695. doi:10.1037/pspp0000210

Tin A, Bressler J, Simino J, et al. Genetic risk, midlife life’s simple 7, and incident dementia in the atherosclerosis risk in communities study .  Neurology . Published online May 25, 2022. doi:10.1212/WNL.0000000000200520 

Levitt M. Perceptions of nature, nurture and behaviour .  Life Sci Soc Policy . 2013;9(1):13. doi:10.1186/2195-7819-9-13

Ross EJ, Graham DL, Money KM, Stanwood GD. Developmental consequences of fetal exposure to drugs: what we know and what we still must learn . Neuropsychopharmacology. 2015 Jan;40(1):61-87. doi: 10.1038/npp.2014.14

World Health Organization. Lead poisoning .

Bandura, A., Ross, D., & Ross, S. A. Transmission of aggression through imitation of aggressive models .  The Journal of Abnormal and Social Psychology, 1961; 63 (3), 575–582 doi:10.1037/h0045925

Krapfl JE.  Behaviorism and society .  Behav Anal.  2016;39(1):123-9. doi:10.1007/s40614-016-0063-8

Bouchard TJ Jr, Lykken DT, McGue M, Segal NL, Tellegen A. Sources of human psychological differences: the Minnesota Study of Twins Reared Apart . Science. 1990 Oct 12;250(4978):223-8. doi: 10.1126/science.2218526

National Institutes of Health.  Common genetic factors found in 5 mental disorders .

Franke HA. Toxic Stress: Effects, Prevention and Treatment . Children (Basel). 2014 Nov 3;1(3):390-402. doi: 10.3390/children1030390

Pain O, Hodgson K, Trubetskoy V, et al.  Identifying the common genetic basis of antidepressant response .  Biol Psychiatry Global Open Sci . 2022;2(2):115-126. doi:10.1016/j.bpsgos.2021.07.008

National Human Genome Research Institute. Eugenics and Scientific Racism .

OLL. The Works of John Locke in Nine Volumes .

Toraño EG, García MG, Fernández-Morera JL, Niño-García P, Fernández AF. The impact of external factors on the epigenome:  in utero  and over lifetime .  BioMed Research International . 2016;2016:1-17. doi:10.1155/2016/2568635

Smith A, Kaufman F, Sandy MS, Cardenas A. Cannabis exposure during critical windows of development: epigenetic and molecular pathways implicated in neuropsychiatric disease .  Curr Envir Health Rpt . 2020;7(3):325-342. doi:10.1007/s40572-020-00275-4

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The Nature vs. Nurture Debate

Genetic and Environmental Influences and How They Interact

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Verywell / Joshua Seong

• Definitions
• Interaction
• Contemporary Views

Nature refers to how genetics influence an individual's personality, whereas nurture refers to how their environment (including relationships and experiences) impacts their development. Whether nature or nurture plays a bigger role in personality and development is one of the oldest philosophical debates within the field of psychology .

Learn how each is defined, along with why the issue of nature vs. nurture continues to arise. We also share a few examples of when arguments on this topic typically occur, how the two factors interact with each other, and contemporary views that exist in the debate of nature vs. nurture as it stands today.

Nature and Nurture Defined

To better understand the nature vs. nurture argument, it helps to know what each of these terms means.

• Nature refers largely to our genetics . It includes the genes we are born with and other hereditary factors that can impact how our personality is formed and influence the way that we develop from childhood through adulthood.
• Nurture encompasses the environmental factors that impact who we are. This includes our early childhood experiences, the way we were raised , our social relationships, and the surrounding culture.

A few biologically determined characteristics include genetic diseases, eye color, hair color, and skin color. Other characteristics are tied to environmental influences, such as how a person behaves, which can be influenced by parenting styles and learned experiences.

For example, one child might learn through observation and reinforcement to say please and thank you. Another child might learn to behave aggressively by observing older children engage in violent behavior on the playground.

The Debate of Nature vs. Nurture

The nature vs. nurture debate centers on the contributions of genetics and environmental factors to human development. Some philosophers, such as Plato and Descartes, suggested that certain factors are inborn or occur naturally regardless of environmental influences.

Advocates of this point of view believe that all of our characteristics and behaviors are the result of evolution. They contend that genetic traits are handed down from parents to their children and influence the individual differences that make each person unique.

Other well-known thinkers, such as John Locke, believed in what is known as tabula rasa which suggests that the mind begins as a blank slate . According to this notion, everything that we are is determined by our experiences.

Behaviorism is a good example of a theory rooted in this belief as behaviorists feel that all actions and behaviors are the results of conditioning. Theorists such as John B. Watson believed that people could be trained to do and become anything, regardless of their genetic background.

People with extreme views are called nativists and empiricists. Nativists take the position that all or most behaviors and characteristics are the result of inheritance. Empiricists take the position that all or most behaviors and characteristics result from learning.

Examples of Nature vs. Nurture

One example of when the argument of nature vs. nurture arises is when a person achieves a high level of academic success . Did they do so because they are genetically predisposed to elevated levels of intelligence, or is their success a result of an enriched environment?

The argument of nature vs. nurture can also be made when it comes to why a person behaves in a certain way. If a man abuses his wife and kids, for instance, is it because he was born with violent tendencies, or is violence something he learned by observing others in his life when growing up?

Nature vs. Nurture in Psychology

Throughout the history of psychology , the debate of nature vs. nurture has continued to stir up controversy. Eugenics, for example, was a movement heavily influenced by the nativist approach.

Psychologist Francis Galton coined the terms 'nature versus nurture' and 'eugenics' and believed that intelligence resulted from genetics. Galton also felt that intelligent individuals should be encouraged to marry and have many children, while less intelligent individuals should be discouraged from reproducing.

The value placed on nature vs. nurture can even vary between the different branches of psychology , with some branches taking a more one-sided approach. In biopsychology , for example, researchers conduct studies exploring how neurotransmitters influence behavior, emphasizing the role of nature.

In social psychology , on the other hand, researchers might conduct studies looking at how external factors such as peer pressure and social media influence behaviors, stressing the importance of nurture. Behaviorism is another branch that focuses on the impact of the environment on behavior.

Nature vs. Nurture in Child Development

Some psychological theories of child development place more emphasis on nature and others focus more on nurture. An example of a nativist theory involving child development is Chomsky's concept of a language acquisition device (LAD). According to this theory, all children are born with an instinctive mental capacity that allows them to both learn and produce language.

An example of an empiricist child development theory is Albert Bandura's social learning theory . This theory says that people learn by observing the behavior of others. In his famous Bobo doll experiment , Bandura demonstrated that children could learn aggressive behaviors simply by observing another person acting aggressively.

Nature vs. Nurture in Personality Development

There is also some argument as to whether nature or nurture plays a bigger role in the development of one's personality. The answer to this question varies depending on which personality development theory you use.

According to behavioral theories, our personality is a result of the interactions we have with our environment, while biological theories suggest that personality is largely inherited. Then there are psychodynamic theories of personality that emphasize the impact of both.

Nature vs. Nurture in Mental Illness Development

One could argue that either nature or nurture contributes to mental health development. Some causes of mental illness fall on the nature side of the debate, including changes to or imbalances with chemicals in the brain. Genetics can also contribute to mental illness development, increasing one's risk of a certain disorder or disease.

Mental disorders with some type of genetic component include autism , attention-deficit hyperactivity disorder (ADHD), bipolar disorder , major depression , and schizophrenia .

Other explanations for mental illness are environmental. This includes being exposed to environmental toxins, such as drugs or alcohol, while still in utero. Certain life experiences can also influence mental illness development, such as witnessing a traumatic event, leading to the development of post-traumatic stress disorder (PTSD).

Nature vs. Nurture in Mental Health Therapy

Different types of mental health treatment can also rely more heavily on either nature or nurture in their treatment approach. One of the goals of many types of therapy is to uncover any life experiences that may have contributed to mental illness development (nurture).

However, genetics (nature) can play a role in treatment as well. For instance, research indicates that a person's genetic makeup can impact how their body responds to antidepressants. Taking this into consideration is important for getting that person the help they need.

Interaction Between Nature and Nurture

Which is stronger: nature or nurture? Many researchers consider the interaction between heredity and environment—nature with nurture as opposed to nature versus nurture—to be the most important influencing factor of all.

For example, perfect pitch is the ability to detect the pitch of a musical tone without any reference. Researchers have found that this ability tends to run in families and might be tied to a single gene. However, they've also discovered that possessing the gene is not enough as musical training during early childhood is needed for this inherited ability to manifest itself.

Height is another example of a trait influenced by an interaction between nature and nurture. A child might inherit the genes for height. However, if they grow up in a deprived environment where proper nourishment isn't received, they might never attain the height they could have had if they'd grown up in a healthier environment.

A newer field of study that aims to learn more about the interaction between genes and environment is epigenetics . Epigenetics seeks to explain how environment can impact the way in which genes are expressed.

Some characteristics are biologically determined, such as eye color, hair color, and skin color. Other things, like life expectancy and height, have a strong biological component but are also influenced by environmental factors and lifestyle.

Contemporary Views of Nature vs. Nurture

Most experts recognize that neither nature nor nurture is stronger than the other. Instead, both factors play a critical role in who we are and who we become. Not only that but nature and nurture interact with each other in important ways all throughout our lifespan.

As a result, many in this field are interested in seeing how genes modulate environmental influences and vice versa. At the same time, this debate of nature vs. nurture still rages on in some areas, such as in the origins of homosexuality and influences on intelligence .

While a few people take the extreme nativist or radical empiricist approach, the reality is that there is not a simple way to disentangle the multitude of forces that exist in personality and human development. Instead, these influences include genetic factors, environmental factors, and how each intermingles with the other.

Schoneberger T. Three myths from the language acquisition literature . Anal Verbal Behav . 2010;26(1):107-31. doi:10.1007/bf03393086

National Institutes of Health. Common genetic factors found in 5 mental disorders .

Pain O, Hodgson K, Trubetskoy V, et al. Identifying the common genetic basis of antidepressant response . Biol Psychiatry Global Open Sci . 2022;2(2):115-126. doi:10.1016/j.bpsgos.2021.07.008

Moulton C. Perfect pitch reconsidered . Clin Med J . 2014;14(5):517-9 doi:10.7861/clinmedicine.14-5-517

Levitt M. Perceptions of nature, nurture and behaviour . Life Sci Soc Policy . 2013;9:13. doi:10.1186/2195-7819-9-13

Bandura A, Ross D, Ross, SA. Transmission of aggression through the imitation of aggressive models . J Abnorm Soc Psychol. 1961;63(3):575-582. doi:10.1037/h0045925

Chomsky N. Aspects of the Theory of Syntax .

Galton F. Inquiries into Human Faculty and Its Development .

Watson JB. Behaviorism .

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Research Paper

Nature vs. nurture research paper.

This sample Nature vs. Nurture Research Paper is published for educational and informational purposes only. Like other free research paper examples, it is not a custom research paper. If you need help with writing your assignment, please use our custom writing services and buy a paper on any of the psychology research paper topics .

Nature vs. Nurture Research Paper Outline

I. Introduction

II. Current Psychological Approaches on Nature Vs Nurture

III. Methods

IV. Applications

VI. Bibliography

Introduction

One of the most persistent issues in the field of psychology is the nature versus nurture debate. This debate concerns how much of an individual, and who s/he is, can be attributed either to nature (i.e., inborn tendencies or genetic factors) or to nurture (i.e., learning or environmental factors). This debate can be one of the most contentious issues in psychology because of the potential serious political ramifications of nature/nurture findings (de Waal, 1999). Although the science of psychology has entered the 21st century, it seems that the nature versus nurture debate will continue to be an active part of psychological research for many areas, including research on intelligence, personality, and mental illness. This research paper will begin with a general overview of the history of the nature/nurture question, focusing on the history of psychology and how psychologists have emphasized the different sides of this debate over time. Next, we discuss current approaches in psychology relevant to the nature/nurture debate and possibly the most controversial aspect of this debate today (i.e., the heritability of intelligence). In addition, the research methods that psychologists have at their disposal to help them determine whether a trait has genetic or environmental influences will be described. Lastly, we discuss the complexities of trying to apply research from the nature versus nurture debate.

The nature versus nurture debate stretches all the way back to the earliest days of Western philosophy, when Plato essentially believed that knowledge was inborn in humans and we merely needed to recollect this knowledge (although Plato did not believe that this was necessarily an easy process). We can firmly place Plato’s position on the nature side of the debate. On the other hand, we can firmly place another major figure in Western philosophy, Aristotle, on the nurture side of the debate. According to Aristotle, true knowledge was not inborn but came from one’s experiences with and observations of the physical world. This debate has been reincarnated repeatedly throughout the history of Western civilization. For instance, many centuries after Plato and Aristotle, the German rationalist Emanuel Kant and the British empiricist John Locke were laying out positions on opposite sides of this same debate. Of course, it was Locke who popularized the notion of the human mind as a tabula rasa (blank slate) at birth, meaning that individuals are not born with innate knowledge; rather, any knowledge or ability that a person eventually attains will have come about through that individual’s experiences. This places Locke firmly on the nurture side of the debate. On the nature side of the debate was Kant. Kant believed that before the mind could make any sense of its experiences there had to be an innate structure to the mind that enabled it to perceive the world and give meaning to one’s experiences. It was this innate ability of the mind that was most important to the attainment of knowledge. Whereas Plato, Aristotle, Locke, and Kant were primarily concerned with how humans can gain knowledge, modern psychologists are more interested in factors such as intelligence, personality, and mental illness. Thus, the nature versus nurture debate has a long history in Western culture (Hergenhahn, 2005). This research paper, however, will focus on the nature versus nurture question in psychology.

Since the early days of modern, scientific one area that has consistently been intertwined with the nature/nurture issue is intelligence. Some of the early leaders in this area of psychology such as Galton and Goddard believed that intelligence was largely inherited. At the time, the zeitgeist (i.e., spirit of the times) emphasized evolutionary theory. So scientists like Galton tended to have a strong bias toward the nature side of the debate. This bias was manifested in Galton’s explanation of his data. Although Galton was the first to conduct twin studies, which continue to be important in the nature/nurture debate, and to study families over time, his bias toward nature led him to underestimate the influence of the environment. When Galton discovered that achievement tends to run in families he concluded that this was evidence that intelligence was inherited. In America, Goddard shared Galton’s view of intelligence. Goddard’s famous “Kallikak” family study traced two lines of a family back to the American Revolutionary War period. Goddard believed that he had identified two sides of a family. One side was intelligent and responsible, whereas the other side was unintelligent and had criminal inclinations. These two sides of the family supposedly began with two different women, one of whom was intelligent and the other feebleminded. So, Goddard interpreted the “Kallikak” family history as supporting the conclusion that intelligence was inherited. Like Galton, Goddard failed to consider important possible environmental factors that can also influence psychological phenomena. Unfortunately, the belief that intelligence was inherited, along with the zeitgeist of applying evolutionary theory to virtually everything, led to some of the most controversial applications in the history of psychology. Galton, for instance, was a strong supporter of eugenics (selective breeding for humans), and he believed that the government should match intelligent people and pay for the education of their children. Even more controversial are some of the policies that Goddard and other psychologists supported, such as the forced sterilization of feebleminded people and dramatically lowering the number of immigrants accepted into America for fear of too many feebleminded people arriving and having too many unintelligent children (Hergenhahn, 2005). Fortunately, this strict view of intelligence’s being inherited and not influenced by the environment would not persist forever.

In the early 20th century a new school of thought in psychology began to dominate the discipline, and this approach swung the pendulum all the way to the opposite end of the debate. Behaviorism emphasized the role of nurture and the environment in influencing individuals and their behavior. John Watson, the founder of behaviorism in America, denied that there were any inherited influences on human behavior. Instead, Watson made the bold claim that if he were given infants, then he could make one a doctor, another a thief, another a painter, and so on. He would merely need to control and manipulate the environment in which an individual developed. Any hereditary factors were unimportant and irrelevant to the development of the individual. So psychology passed into a period when there was a strong bias toward the nurture side of the debate (Hergenhahn, 2005). This emphasis on the environment was so strong that many psychologists believed that a phenomenon like the infant-mother bond was not in any way related to nature. Instead, it was argued that the infant-mother bond developed as a result of the mother (a neutral stimulus) being paired with primary reinforcers (e.g., food, milk, etc.).

Harlow challenged this assumption that the infant-mother bond was due only to nurture (i.e., learning). Harlow (1958) raised infant monkeys with two surrogate mothers. One surrogate mother had a body composed of wire mesh. This wire mesh mother provided the milk to the infant monkey. The second surrogate mother did not provide any food, but its body was covered with a soft terry cloth. Harlow found that the infant monkeys clung to the terry-cloth-covered mother, not to the wire mesh mother that provided the milk. This finding contradicted the behaviorist assumption that the reason for the mother-infant bond was that the mother became associated with food (i.e., the mother essentially becomes a secondary reinforcer). Instead, Harlow’s (1958) research suggested that there was a biological need for “contact comfort” (p. 676) that had more influence on the mother-infant bond. In addition to Harlow’s study, there was additional research that was demonstrating that the behaviorists had gone too far when they concluded that nature did not need to be considered in the development of the organism (Hergenhahn & Olson, 2005). Research by Marian and Keller Breland, for instance, identified the phenomenon of instinctual drift where an instinct would displace an earlier learned behavior, so that a behavior that was initially brought about by the environment was displaced by the biological instinct of the organism (Hergenhahn & Olson, 2005). In addition, other research on the Garcia effect, or conditioned taste aversion, found that the biology of the organism did indeed need to be considered in learning and in the wider field of psychology. This trend toward a recognition of the biological factors that can influence the behavior of the individual continued and eventually led to the development of evolutionary psychology. In evolutionary psychology, researchers focus on the biological design of the organism and on how certain behaviors developed over time because they were adaptive (enabling the organism to survive long enough in a particular environment to have offspring, and also enabling an organism to assist those she or he is biologically related to and so also pass genes into the future in that way). As biological influences on behavior and cognition became more and more evident, the field of behavioral genetics developed. Behavioral genetics is the field of psychobiology that examines all the genetic factors that impact on behavior and cognition (Hergenhahn, 2005).

Current Psychological Approaches on Nature Vs Nurture

Today there are a number of approaches that are relevant to the nature/nurture issue in psychology. The first of those areas is behavioral genetics, which has grown into a very respectable and popular area of study. Behavioral genetics focuses on identifying the heritability of psychological traits, such as intelligence and personality. Heritability is “an estimate of the size of the genetic effect” (Dunn & Plomin, 1990, p. 32) for a particular trait. Twin and adoption studies are among the methods that behavioral geneticists use to determine heritability. These methods will be discussed in more detail later in this research paper.

The field of behavioral genetics has been able to conclusively demonstrate the importance of nature on many psychological traits. For instance, estimates for the heritability of intelligence range from 0.50 to 0.80 (Hergenhahn, 2005). This means that genetic factors account for 50 to 80 percent of the variance for intelligence. The heritability of manic depression (bipolar affective disorder) is around 67 percent; for depression, 60 percent; and for schizophrenia, 79 percent (Steen, 1996). In addition, estimates for the heritability of various personality traits are 47 percent for extroversion, 46 percent for openness, 46 percent for neuroticism, 40 percent for conscientiousness, and 39 percent for agreeableness (Steen, 1996). So, research has determined that nature is indeed an important determiner of who we are.

Although the field of behavioral genetics has demonstrated the importance of heritability to a plethora of psychological traits, the same findings also lead to the conclusion that environment too plays an important part in these psychological phenomena. Even though research findings concerning how much of a trait like intelligence is due to our genes is often widely disseminated in the media, the other side of the coin is nurture. Any variance that is not due to genes is by definition due to environment (Steen, 1996). Nature never accounts for 100 percent of the variance for any psychological trait. Instead, psychological traits are most likely the result of a number of interacting genes that account for a large part of the variance for a particular trait. However, the remaining variance that is due to environment remains important. So, if 47 percent of the variance for the trait of extroversion is attributable to genes, then that means that 53 percent of the variance for extroversion is due to the environment. Perhaps environmental factors are not discussed as often in the media because there are many possible environmental factors that can be involved, ranging from parenting style to culture to a viral infection.

In the past, the part of the environment that has perhaps been assumed as having the most influence on psychological traits is the shared family environment. Much past research has compared children from different families to one another, assuming that all the children from one family must all experience the same family environment (Dunn & Plomin, 1990). Behavioral geneticists, however, have found that the shared family environment has little effect on personality traits. The amount of variance for personality traits that can be accounted for by the shared family environment is around 5 percent (Hergenhahn, 2005). Dunn and Plomin (1990) point out that anecdotally the differences between siblings exceed the similarities, as most people with brothers and sisters can attest. Indeed, the correlations between siblings for a variety of traits are astonishingly low. A correlation of 0.50 between siblings would mean that they “are different and similar in about equal measure” (Dunn & Plomin, 1990, p. 10). If the correlation were higher than 0.50, then the siblings would be more similar to one another than different. However, if the correlation were lower than 0.50, then the siblings would be more different from one another than similar to one another. The correlations between siblings for many personality traits are very low (e.g., extraversion is 0.25 and neuroticism is 0.07). These low correlations support the conclusion that shared family environment, long the focus of many studies of nurture’s influence, is not a key determiner of psychological traits. Because siblings differ so substantially from one another, it makes sense that any part of the family environment that they experience similarly to one another is not relevant to these differences. Instead, it is those aspects of the family environment that are experienced differently that are more relevant to the development of psychological traits (Dunn & Plomin, 1990). So, one focus of recent studies on the influence of environment has been on nonshared environmental factors. Most likely, this will remain a focus for studies of the environment and how it influences psychological traits well into the 21st century.

With behavioral geneticists demonstrating the importance of both genes and the environment on psychological traits, theoretical approaches are beginning to focus on explaining how nature and nurture interact. More barriers between subfields in psychology and between disciplines are being broken down, resulting in more integrated and interactionist models of development (de Waal, 1999). Dai and Coleman (2005), for instance, state that a monistic view of giftedness as being the sole result of nature is no longer a supportable position. An example of a more interactionist perspective is a multiplier effect, which refers to how a single, small factor may ultimately have a large effect on a trait or talent because that small factor interacts with and creates a chain of reactions that multiply over time into the ultimate output for the giftedness (Papierno, Ceci, Makel, & Williams, 2005). So, very small changes in an individual’s genetic makeup (consisting of one gene being present or absent, or perhaps consisting of a number of genes each only contributing a small percentage of variance), an individual’s environment (such as having a brother vs. a sister), or an individual’s culture (such as being raised in a collectivist vs. individualistic culture) can be the impetus that sets into motion a set of reciprocal interactions that ultimately results in the individual developing into a gifted person capable of successfully composing touching and enjoyable music. These multiplier effects are key components of bioecological models of human development. Bioecological models have come to recognize how genes and environment can create feedback loops in which they push a particular trait to develop further and further. The ultimate example of this would be what is called the Matthew Effect. The Matthew Effect essentially states “that initial advantage begets future advantage” (Papierno et al., 2005). For instance, perhaps a child has an initial genetic advantage in verbal ability, so the child talks more to her parents. The parents, of course, notice and respond to this by reading more to the child and reinforcing a wider variety of verbal responses from the child. This leads to the child having better verbal ability when she begins school, and so on. This continues until she one day writes the great American novel of the 21st century, or that is the possibility.

Even though the focus of most psychologists today is on the interaction of nature and nurture, there are still some theoretical approaches that emphasize the importance of nurture. Ericsson, Nandagopal, and Roring (2005) argue for the nurture side of the debate. They argue that expert performance does not rely on an inherited talent or giftedness; rather, expert performance is the result of acquired abilities that have been developed through extended deliberate practice. Ericsson et al. (2005) argue that evidence supports the conclusion that, contrary to experts in a given domain being born, before one can perform expertly in a given domain he or she must have prolonged experience in that field. Furthermore, they point out that a person’s performance in a specific area improves gradually over time and with experience; even the performance of so-called child prodigies follows this pattern. Ericsson et al. also argue that the historical improvements in performance over the last 100 years support the conclusion that expert performance is not due to innate talent. They point out that if talent were genetic, then improvements in talent over the last 100 years would not be possible because genes would fix an upper limit on talent that could not change dramatically in so short a time period. So according to Ericsson et al., their expert-performance framework attributes differences in expert performance (even among so-called prodigies) to acquired cognitive and physiological changes that are the result of extended deliberate practice.

Although psychology in the 21st century is a scientific field that has developed many methods to investigate psychological phenomena, and our understanding of development has become more sophisticated, the nature versus nurture debate remains very active. An example of part of this continuing debate that will exist for the foreseeable future is the heritability of intelligence. Since Galton and Goddard argued that intelligence is essentially inherited, there have been researchers who have supported this conclusion. Over the years aspects of this debate have become part of the more unseemly beliefs of racism. Not that those who conclude that intelligence is inherited are racist, but that conclusion has in the past been partly motivated by racist beliefs against immigrants. This should demonstrate how volatile the nature versus nurture debate can be and how potentially important and influential research findings in this area are. In 1994 Herrnstein and Murray argued that intelligence was indeed a general cognitive ability on which humans differ, that IQ scores do not fluctuate much over the life span, and most importantly, that intelligence is largely heritable. Although behavioral genetic research tends to support the conclusion that intelligence is indeed substantially influenced by nature, most researchers today emphasize an interactionist perspective that recognizes the importance of both nature and nurture even when perhaps a majority of a trait, like intelligence, might be attributable to nature.

There are a number of important criticisms of the conclusion that intelligence is inherited. These criticisms can also be applied to many other traits and the belief that they are largely inherited. First, just because a test for a particular trait such as intelligence has been developed, that does not mean that the trait actually exists as an independent construct. Hanson (1996) argues, “When a given test becomes sufficiently important, whatever that test tests gets reified as a single quality of thing” (p. 112). Although intelligence tests have existed for over 100 years, it is tempting to assume that intelligence as an objective phenomenon does exist; however, critics warn not to reify a psychological trait just because we have named it and developed tests to measure it. So, if we cannot be sure of its objective existence, then how can we conclude that it is heritable? Another equally important criticism concerns disagreements over how to define intelligence. Intelligence tests that are currently in widespread use do not attempt to measure every kind of intelligence that has been proposed (Gardner, 1996). Intelligence tests measure only what they are designed to measure. Furthermore, any test is an indirect and inaccurate measure that is constantly being changed to measure the trait more accurately (Hanson, 1996). So, if researchers disagree on how to define intelligence and if intelligence tests keep changing over time, how can we conclude that intelligence is heritable? One last criticism of the conclusion that intelligence is heritable concerns the fact that heritability is a descriptive statistic of the amount of variance that can be attributed to genes for a particular trait in a specific sample of individuals. Descriptive statistics are used to describe a specific group of individuals. It is not appropriate to generalize descriptive statistics for one sample to other people. Thus, critiques point out that you cannot identify how much of a particular trait is genetic in one group of people and assume that this will be the same in other people everywhere.

The debate concerning the heritability of intelligence is one example of a continuing issue, and a vigorous one at that, in the nature versus nurture debate. Providing viewpoints from both sides of the debate demonstrates some of the complexities that will continue to keep this debate an important part of psychology over the next century. Although some still argue that either nature or nurture is the most important influence on human beings and their psychological traits, the future seems to be focused on interactionist approaches that will attempt to better explain how nature and nurture interact to make us who we are psychologically.

In psychology today, researchers have a number of methods that help them to identify the extent to which nature and nurture influence psychological traits. First, twin studies involve the comparison of identical and fraternal twins. Identical twins develop from the same fertilized egg, so they are called monozygotic (MZ) twins. Identical twins have the same genetic makeup, so their genetic relatedness is 100 percent. Thus, any differences found between identical twins can be attributed to the environment (i.e., nurture). Fraternal twins, on the other hand, develop from two separate fertilized eggs, so they are referred to as dizygotic (DZ) twins. Fraternal twins are like any two siblings with a genetic relatedness of 50 percent. This difference between identical and fraternal twins in genetic relatedness is key to drawing conclusions about nature and nurture from twin studies. With this basic knowledge of genetic relatedness of twins one can make conclusions based on correlations between twins on a particular psychological trait. If a trait is influenced by nature (heredity), then researchers should find that fraternal twins are more variable (or different) on that trait as compared to identical twins. Because identical twins have the exact same genetic input, researchers should not observe any differences between them on a trait that is hereditary in nature. However, if a particular trait is not influenced by nature, then researchers should find that identical twins are not any more similar to each other on that trait than fraternal twins are to each other (Dunn & Plomin, 1990; Plomin, 1990). Another method that researchers use to study the influence of nature and nurture on psychological traits is adoption studies. Some adoption studies examine individuals who are not genetically related to one another, however they all live in the same environment (i.e., family). Other adoption studies examine individuals who are genetically related to one another, but they are raised in different environments. If nature is a key component for a trait, then individuals who are genetically related to one another (irrespective of their environments) should be similar on that trait. However, if nurture is a key component of a trait, then individuals who share a particular environment should be similar on that trait (irrespective of their genetic relatedness; Dunn & Plomin, 1990).

Researchers can use twin and adoption studies to estimate the heritability of traits. It should be made clear that heritability is a descriptive statistic that estimates the size of a genetic effect for a particular trait in a specific group of people. So, heritability merely describes a genetic effect for individuals in a particular study. Heritability is not “an immutable constant” (Dunn & Plomin, 1990, p. 33) that researchers can generalize to all people (Steen, 1996). Instead, heritability estimates the effect size for genetics in a particular group, at a particular time, and even in a particular environment. So when researchers identify the heritability of a trait, that does not mean that that same heritability will necessarily apply for that trait in other people (Dunn & Plomin, 1990).

Feral children provide another opportunity to study the nature/nurture issue. Typically, the cases of feral children get much more attention than the normal, more scientific methods of researchers. Feral children are children who appear to grow up in the wild or to be brought up by animals. These children seem to have had very little, or no, human contact while they were growing up. Feral children would seem to support the conclusion that experiences (i.e., nurture) are important to the normal development of the human brain. If these children experienced deprived environments in their youth, then these deficient environments led to them developing very poorly and with many cognitive deficits compared to normal human children. As promising for studying the nature/nurture issue as these cases might seem to be, they are few and far between, so they amount to nothing more than case studies that capture a lot of attention. Candland (1993) discusses the stories of many feral children such as Peter, Victor (the Wild Boy of Aveyron), and the wolf-girls of India. In the end, however, real-life examples of feral children have too many unanswered questions to provide accurate information concerning the nature/nurture debate. For instance, exactly where and when were these children abandoned, and exactly why were these children abandoned? It may be that these children were severely disabled to begin with and this may be the very reason that they were abandoned in the first place. If this is so, then these children really do not provide unique information about the nature/nurture issue. As is usually the case with real-world examples, the number of uncontrolled factors is so numerous that no conclusive data can be obtained from the reported cases of feral children. Nonetheless, these cases will continue to garner a large amount of attention, and they provide a more human face and emotional connection to the nature/ nurture debate.

Yet another naturally occurring phenomenon that garners much attention, and on the surface seems ideal for studying the influence of nature versus nurture, is the existence of savants. The term savant is used to refer to those who have an outstanding ability in one area or skill while simultaneously having a more general intellectual deficiency (Miller, 2005). Researchers and theorists have used the existence of a unique and an especially astute ability in a specific area as one part of the evidence for specific or multiple intelligences (Gardner, 1983). Because this one ability is intact, yet other abilities are not, it suggests that there are specific innate abilities for this sort of “intelligence” that the savant displays. On the other hand, some argue that savants may focus all of their attention on one ability or skill and develop it through practice (Miller, 2005). So again the complications of naturally occurring phenomena block researchers from making firm conclusions regarding nature versus nurture from savants.

Research that will help to investigate the different influences of nonshared environments deserves consideration. These studies should focus on studying multiple individuals who are raised in the same family. This approach will allow researchers to begin to understand how each child in a family has a unique environmental experience. Not only will different children in the same family have nonshared environmental experiences, but each child may be differentially affected by the same environmental stimulus such as mom or dad (Dunn & Plomin, 1990). Examining these nonshared environmental factors and how different children in the same family experience the same environmental stimulus differentially will require detailed study over an extended period of time, including having parents and siblings answer detailed questionnaires concerning their childhood and current psychological traits. In addition, researchers need to conduct longitudinal studies following children throughout their childhood and into adulthood to identify and understand these developmental processes.

Psychology has developed many useful research methods to study nature versus nurture, including twin studies and adoption studies. Psychologists have also been able to study some naturally occurring phenomena, such as feral children and savants, to help understand the influences of nature and nurture. Future studies will likely focus more on nonshared environmental factors. In addition, as medical technology becomes more and more sophisticated and as researchers are able to identify specific genes that influence psychological traits, researchers will be able to test individuals for the presence of these genes and determine just how much a particular gene might influence the development of something like schizophrenia.

Applications

Research investigating the nature and nurture issue in a variety of areas (e.g., intelligence, personality, mental illness, etc.) has potential applications. Knowledge about the causes for mental illnesses, for instance, directly affects the treatment that professionals will use for people suffering from those illnesses. For example, the discovery of substantial heritability rates for some mental illnesses, such as bipolar disorder, supports the continuing medical search for biological treatments, such as drugs. Furthermore, knowledge concerning exactly what parts of the environment influence mental illness can help psychologists to develop more targeted psychological treatments. In addition, the extent to which researchers believe that intelligence and personality are influenced by the environment can help to determine educational approaches from preschool through college.

One potential danger in applications from research on nature versus nurture concerns concluding that nurture is the primary influence on development, thus leading to the erroneous conclusion, once held by the behaviorists, that biology and basic human needs do not need to be considered when designing or implementing educational or other service programs. A more detailed discussion and critique of denying nature’s influence on human beings is provided by Pinker (2002). Pinker discusses the historical influence of the notion of the human mind as a blank slate and how that can lead to a plethora of problems when trying to design and implement social service programs and create public policy.

On the opposite side of the debate, another danger is prematurely attributing the majority of a particular trait to nature or genes. Especially if researchers determine that a “deficiency” is attributable to genetics, then the temptation is to assume that nurture (or the environment) cannot influence it, and therefore there is a temptation to make no attempt to improve that person’s lot in life (Candland, 1993). Even if the majority of a trait is due to nature we make a mistake to assume that nature and nurture are mutually exclusive (Candland, 1993). Instead, even if the majority of a trait might be attributable to genes, some of the trait is still attributable to nurture. Furthermore, genes and the environment always interact in their expression. Genotype refers to an organism’s genetic makeup, whereas phenotype refers to an organism’s actual attributes and characteristics (Burdon, 1999). So, a person’s genes might set the range for how tall a person will be (say from 5 feet 5 inches to 6 feet 5 inches), but the environment in which a person grows up will determine where in that range the person develops. So, if individuals live in a restricted nutritional environment, they will develop at the lower part of the range, and if they develop in a nutritionally rich environment, they will develop to the higher end of the range and be taller. So, any genotype (no matter how strong) interacts with the environment to manifest a final phenotype in the individual. If this is true for a simple trait like height, then how much more so will more complicated traits, such as intelligence (whose genetic component is likely due to an interacting cluster of genes), be influenced by the environment? Therefore, when applying research from the influence of nature on psychological traits, policy makers should keep in mind that no matter how much of a trait is attributable to genetics, nurture always plays a role in the final expression of that trait. Therefore, researchers always must take nurture seriously as an interacting factor that contributes to our development and psychological characteristics. Furthermore, policy makers must remember that science (including psychology) is a field of study that attempts to provide more and more accurate knowledge over time. So, current conclusions regarding the influence of nature and nurture will change over time as our knowledge gets better. This means that applications should also be changed as scientific knowledge improves; hence, policy makers need to remain knowledgeable concerning the constantly changing conclusions in the nature versus nurture debate.

The nature versus nurture debate has a long history in Western philosophy and modern psychology. The debate is relevant to many different areas of study in psychology, including intelligence, giftedness, sexual orientation, personality, and mental illness. Today, most psychologists take an interactionist approach that views both nature and nurture as being important in development. However, some researchers still emphasize either nature or nurture as being the key component that determines a psychological trait. Many psychological researchers will continue to use tried-and-true research methods such as twin and adoption studies to examine the nature/nurture issue; however, future genetic research will identify more genes that influence behavioral and psychological phenomena. Future research on environmental factors will focus on the importance of nonshared environments and how different children in the same family might experience the same environmental stimulus in different ways, thus having a very different influence on their development. Research findings regarding nature and nurture will continue to be among the most applicable aspects of psychological studies, but they will likely also remain among the most politically volatile issues in the field.

Bibliography:

• Burdon, R. H. (1999). Genes and environment. Philadelphia: Taylor and Francis.
• Candland, D. K. (1993). Feral children & clever animals: Reflections on human nature. New York: Oxford University Press.
• Collins, W. A., Maccoby, E. E., Steinberg, L., Hetherington, E. M., & Bornstein, M. H. (2000). Contemporary research on parenting: The case for nature and nurture. American Psychologist, 55, 218–232.
• Dai, D. Y., & Coleman, L. J. (2005). Epilogue: Conclusions and implications for gifted education. Journal for the Education of the Gifted, 28, 374–388.
• de Waal, F. B. M. (1999). The end of nature versus nurture. Scientific American, 281, 94–99.
• Dunn, J., & Plomin, R. (1990). Separate lives: Why siblings are so different. New York: Basic Books.
• Ericsson, K. A., Nandagopal, K., & Roring, R. W. (2005). Giftedness viewed from the expert-performance perspective. Journal for the Education of the Gifted, 28, 287–311.
• Gardner, H. (1983). Frames of mind: The theory of multiple intelligences. New York: Basic Books.
• Gardner, H. (1996). IQ tests do not measure all kinds of intelligence. In T. L. Roleff (Ed.), Genetics and intelligence (pp. 115–119). San Diego, CA: Greenhaven Press, Inc.
• Hanson, F. A. (1996). IQ tests measure learned knowledge. In T. L. Roleff (Ed.), Genetics and intelligence (pp. 106–114). San Diego, CA: Greenhaven Press, Inc.
• Harlow, H. F. (1958). The nature of love. American Psychologist, 13, 673–685.
• Hergenhahn, B. R. (2005). An introduction to the history of psychology (5th ed.). Belmont, CA: Thomson Wadsworth.
• Hergenhahn, B. R., & Olson, M. H. (2005). An introduction to theories of learning (7th ed.). Upper Saddle River, NJ: Pearson Prentice Hall.
• Herrnstein, R. J., & Murray, C. (1994). The bell curve: Intelligence and class structure in American life. New York: Free Press.
• Miller, L. K. (2005). What the savant syndrome can tell us about the nature and nurture of talent. Journal for the Education of the Gifted, 28, 361–373.
• Papierno, P. B., Ceci, S. J., Makel, M. C., & Williams, W. M. (2005). The nature and nurture of talent: A bioecological perspective on the ontogeny of exceptional abilities. Journal for the Education of the Gifted, 28, 312–332.
• Pinker, S. (2002). The blank slate: The modern denial of human nature. New York: Viking.
• Plomin, R. (1990). Nature and nurture: An introduction to human behavioral genetics. Pacific Grove, CA: Brooks/ Cole Publishing Company.
• Roleff, T. L. (Ed.). (1996). Genetics and intelligence. San Diego, CA: Greenhaven Press, Inc.
• Steen, R. G. (1996). DNA and destiny: Nature and nurture in human behavior. Cambridge, MA: Perseus Publishing.
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