Nature versus nurture
Nature versus nurture is a long-standing debate in biology and society about the relative influence on human beings of their genetic inheritance or biology and the environmental conditions of their development. Nature is what people think of as pre-wiring and is influenced by genetic inheritance and other biological factors. Nurture is generally taken as the influence of external factors after conception e.g. the product of exposure, experience, and learning on an individual.
The phrase in its modern sense was popularized by the Victorian polymath Francis Galton, the modern founder of eugenics and behavioral genetics when he was discussing the influence of heredity and environment on social advancement. Galton was influenced by On the Origin of Species written by his half-cousin, the evolutionary biologist Charles Darwin. The complementary combination of the two concepts is an ancient concept.
The view that humans acquire all or almost all their behavioral traits from "nurture" was termed tabula rasa by John Locke in 1690. A blank slate view in human developmental psychology, which assumes that human behavioral traits develop almost exclusively from environmental influences, was widely held during much of the 20th century. The debate between "blank-slate" denial of the influence of heritability, and the view admitting both environmental and heritable traits, was at the core of an ideological dispute over research agendas throughout the second half of the 20th century.
Today, the idea of a strong dichotomy of nature versus nurture is generally considered to have limited relevance. Both "nature" and "nurture" factors have been found to contribute substantially, often in an inextricable manner, to many processes studied by biologists, psychologists and anthropologists. Feedback loops have been found in which nature and nurture influence one another constantly, as seen in self-domestication. In ecology and behavioral genetics, researchers posit that nurture has an essential influence on the nature of an individual. Similarly in other fields, the dividing line between an inherited and an acquired trait has become unclear, as in epigenetics and fetal development.
History of the debate
According to Records of the Grand Historian by Sima Qian, during Chen Sheng Wu Guang uprising in 209 B.C., Chen Sheng asked the rhetorical question as a call to war: "Are kings, generals, and ministers merely born into their kind?". Though Chen was obviously negative to the question, the phrase has often been cited as an early quest into the nature versus nurture problem.John Locke's An Essay Concerning Human Understanding is often cited as the foundational document of the blank slate view. In the Essay, Locke specifically criticizes René Descartes's claim of an innate idea of God that is universal to humanity. Locke's view was harshly criticized in his own time. Anthony Ashley-Cooper, 3rd Earl of Shaftesbury, complained that by denying the possibility of any innate ideas, Locke "threw all order and virtue out of the world," leading to total moral relativism. By the 19th century, the predominant perspective was contrary to that of Locke's, tending to focus on "instinct." Leda Cosmides and John Tooby noted that William James argued that humans have more instincts than animals, and that greater freedom of action is the result of having more psychological instincts, not fewer.
The question of "innate ideas" or "instincts" was of some importance in the discussion of free will in moral philosophy. In 18th-century philosophy, this was cast in terms of "innate ideas" establishing the presence of a universal virtue, a prerequisite for objective morals. In the 20th century, this argument was in a way inverted, since some philosophers now argued that the evolutionary origins of human behavioral traits forces us to concede that there is no foundation for ethics, while others treated ethics as a field of cognitively valid statements in complete isolation from evolutionary considerations.
Early to mid-20th century
In the early 20th century, there was an increased interest in the role of one's environment, as a reaction to the strong focus on pure heredity in the wake of the triumphal success of Darwin's theory of evolution. During this time, the social sciences developed as the project of studying the influence of culture in clean isolation from questions related to "biology. Franz Boas's The Mind of Primitive Man established a program that would dominate American anthropology for the next 15 years. In this study, he established that in any given population, biology, language, material, and symbolic culture, are autonomous; that each is an equally important dimension of human nature, but that none of these dimensions is reducible to another.Purist behaviorism
in the 1920s and 1930s established the school of purist behaviorism that would become dominant over the following decades. Watson is often said to have been convinced of the complete dominance of cultural influence over anything that heredity might contribute. This is based on the following quote which is frequently repeated without context, as the last sentence is frequently omitted, leading to confusion about Watson's position:During the 1940s to 1960s, Ashley Montagu was a notable proponent of this purist form of behaviorism which allowed no contribution from heredity whatsoever: In 1951, Calvin Hall suggested that the dichotomy opposing nature to nurture is ultimately fruitless.In African Genesis and The Territorial Imperative, Robert Ardrey argues for innate attributes of human nature, especially concerning territoriality. Desmond Morris in The Naked Ape expresses similar views. Organised opposition to Montagu's kind of purist "blank-slatism" began to pick up in the 1970s, notably led by E. O. Wilson.
The tool of twin studies was developed as a research design intended to exclude all confounders based on inherited behavioral traits. Such studies are designed to decompose the variability of a given trait in a given population into a genetic and an environmental component. Studies using twin neuroimaging methods show that genetic elements explain more of the variation in cognitive processing than emotional regulation which indicates that environmental factors play a greater role in shaping affective traits. Twin studies established that there was, in many cases, a significant heritable component. These results did not, in any way, point to overwhelming contribution of heritable factors, with heritability typically ranging around 40% to 50%, so that the controversy may not be cast in terms of purist behaviorism vs. purist nativism. Rather, it was purist behaviorism that was gradually replaced by the now-predominant view that both kinds of factors usually contribute to a given trait, anecdotally phrased by Donald Hebb as an answer to the question "which, nature or nurture, contributes more to personality?" by asking in response, "Which contributes more to the area of a rectangle, its length or its width?"
In a comparable avenue of research, anthropologist Donald Brown in the 1980s surveyed hundreds of anthropological studies from around the world and collected a set of cultural universals. He identified approximately 150 such features, coming to the conclusion there is indeed a "universal human nature", and that these features point to what that universal human nature is.
Determinism
At the height of the controversy, during the 1970s to 1980s, the debate was highly ideologised. In Not in Our Genes: Biology, Ideology and Human Nature, Richard Lewontin, Steven Rose and Leon Kamin criticise "genetic determinism" from a Marxist framework, arguing that "Science is the ultimate legitimator of bourgeois ideology... If biological determinism is a weapon in the struggle between classes, then the universities are weapons factories, and their teaching and research faculties are the engineers, designers, and production workers." The debate thus shifted away from whether heritable traits exist to whether it was politically or ethically permissible to admit their existence. The authors deny this, requesting that evolutionary inclinations be discarded in ethical and political discussions regardless of whether they exist or not.1990s
Heritability studies became much easier to perform, and hence much more numerous, with the advances of genetic studies during the 1990s. By the late 1990s, an overwhelming amount of evidence had accumulated that amounts to a refutation of the extreme forms of "blank-slatism" advocated by Watson or Montagu.This revised state of affairs was summarized in books aimed at a popular audience from the late 1990s. In The Nurture Assumption: Why Children Turn Out the Way They Do, Judith Rich Harris was heralded by Steven Pinker as a book that "will come to be seen as a turning point in the history of psychology." However, Harris was criticized for exaggerating the point of "parental upbringing seems to matter less than previously thought" to the implication that "parents do not matter."
The situation as it presented itself by the end of the 20th century was summarized in The Blank Slate: The Modern Denial of Human Nature by Steven Pinker. The book became a best-seller, and was instrumental in bringing to the attention of a wider public the paradigm shift away from the behaviourist purism of the 1940s to 1970s that had taken place over the preceding decades.
Pinker portrays the adherence to pure blank-slatism as an ideological dogma linked to two other dogmas found in the dominant view of human nature in the 20th century:
- "noble savage", in the sense that people are born good and corrupted by bad influence; and
- "ghost in the machine", in the sense that there is a human soul capable of moral choices completely detached from biology.