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The Nurture Assumption

Why Children Turn Out the Way They Do, Revised and Updated



About The Book

This groundbreaking book, a Pulitzer Prize finalist and New York Times notable pick, rattled the psychological establishment when it was first published in 1998 by claiming that parents have little impact on their children's development. In this tenth anniversary edition of The Nurture Assumption, Judith Harris has updated material throughout and provided a fresh introduction.

Combining insights from psychology, sociology, anthropology, primatology, and evolutionary biology, she explains how and why the tendency of children to take cues from their peers works to their evolutionary advantage. This electrifying book explodes many of our unquestioned beliefs about children and parents and gives us a radically new view of childhood.



Heredity and environment. They are the yin and yang, the Adam and Eve, the Mom and Pop of pop psychology. Even in high school I knew enough about the subject to inform my parents, when they yelled at me, that if they didn't like the way I was turning out they had no one to blame but themselves: they had provided both my heredity and my environment.

"Heredity and environment" -- that's what we called them back then. Nowadays they are more often referred to as "nature and nurture." Powerful as they were under the names they were born with, they are yet more powerful under their alliterative aliases. Nature and nurture rule. Everyone knows it, no one questions it: nature and nurture are the movers and shapers. They made us what we are today and will determine what our children will be tomorrow.

In an article in the January 1998 issue of Wired, a science journalist muses about the day -- twenty? fifty? a hundred years from now? -- when parents will be able to shop for their children's genes as easily as today they shop for their jeans. "Genotype choice," the journalist calls it. Would you like a girl or a boy? Curly hair or straight? A whiz at math or a winner of spelling bees? "It would give parents a real power over the sort of people their children will turn out to be," he says. Then he adds, "But parents have that power already, to a large degree."

Parents already have power over the sort of people their children will turn out to be, says the journalist. He means, because parents provide the environment. The nurture.

No one questions it because it seems self-evident. The two things that
determine what sort of people your children will turn out to be are nature -- their genes -- and nurture -- the way you bring them up. That is what you believe and it also happens to be what the professor of psychology believes. A happy coincidence that is not to be taken for granted, because in most sciences the expert thinks one thing and the ordinary citizen -- the one who used to be called "the man on the street" -- thinks something else. But on this the professor and the person ahead of you on the checkout line agree: nature and nurture rule. Nature gives parents a baby; the end result depends on how they nurture it. Good nurturing can make up for many of nature's mistakes; lack of nurturing can trash nature's best efforts.

That is what I used to think too, before I changed my mind.

What I changed my mind about was nurture, not environment. This is not going to be one of those books that says everything is genetic; it isn't. The environment is just as important as the genes. The things children experience while they are growing up are just as important as the things they are born with. What I changed my mind about was whether "nurture" is really a synonym for "environment." Using it as a synonym for environment, I realized, is begging the question.

"Nurture" is not a neutral word: it carries baggage. Its literal meaning
is "to take care of" or "to rear"; it comes from the same Latin root that
gave us nourish and nurse (in the sense of "breast-feed"). The use of "nurture" as a synonym for "environment" is based on the assumption that what influences children's development, apart from their genes, is the way their parents bring them up. I call this the nurture assumption. Only after rearing two children of my own and coauthoring three editions of a college textbook on child development did I begin to question this assumption. Only recently did I come to the conclusion that it is wrong.

It is difficult to disprove assumptions because they are, by definition, things that do not require proof. My first job is to show that the nurture assumption is nothing more than that: simply an assumption. My second is to convince you that it is an unwarranted assumption. My third is to give you something to put in its place. What I will offer is a viewpoint as powerful as the one it replaces -- a new way of explaining why children turn out the way they do. A new answer to the basic question of why we are the way we are. My answer is based on a consideration of what kind of mind the child is equipped with, which requires, in turn, a consideration of the evolutionary history of our species. I will ask you to accompany me on visits to other times and other societies. Even chimpanzee societies.

Beyond a Reasonable Doubt?

How can I question something for which there is so much evidence? You can see it with your own eyes: parents do have effects on their kids. The child who has been beaten looks cowed in the presence of her parents. The child whose parents have been wimpy runs rampant over them. The child whose parents failed to teach morality behaves immorally. The child whose parents don't think he will accomplish much doesn't accomplish much.

For those doubting Thomases who have to see it in print, there are books full of evidence -- thousands of books. Books written by clinical psychologists like Susan Forward, who describes the devastating and longlasting effects of "toxic parents" -- overcritical, overbearing, underloving, or unpredictable people who undermine their children's self-esteem and autonomy or give them too much autonomy too soon. Dr. Forward has seen the damage such parents wreak on their children. Her patients are in terrible shape psychologically and it is all their parents' fault. They won't get better until they admit, to Dr. Forward and themselves, that it is all their parents' fault.

But perhaps you are among those doubting Thomases who don't consider the opinions of clinical psychologists, formed on the basis of conversations with a self-selected sample of troubled patients, to be evidence. All right, then, there is evidence of a more scientific sort: evidence obtained in carefully designed studies of ordinary parents and their children -- parents and children whose psychological well-being varies over a wider range than you could find in Dr. Forward's waiting room.

In her book It Takes a Village, First Lady Hillary Rodham Clinton has summarized some of the findings from the carefully designed studies carried out by developmental psychologists. Parents who care for their babies in a loving, responsive way tend to have babies who are securely attached to them and who develop into self-confident, friendly children. Parents who talk to their children, listen to them, and read to them tend to have bright children who do well in school. Parents who provide firm -- but not rigid -- limits for their children have children who are less likely to get into trouble. Parents who treat their children harshly tend to have children who are aggressive or anxious, or both. Parents who behave in an honest, kind, and conscientious manner with their children are likely to have children who also behave in an honest, kind, and conscientious manner. And parents who fail to provide their children with a home that contains both a mother and a father have children who are more likely to fail in some way in their own adult lives.

These statements, and others of a similar sort, are not airy speculation. There is a tremendous amount of research to back them up. The textbooks I wrote for undergraduates taking college courses in child development were based on the evidence produced by that research. The professors who teach the courses believe the evidence. So do the journalists who occasionally report the results of a study in a newspaper or magazine article. The pediatricians who give advice to parents base much of their advice on it. Other advice-givers who write books and newspaper articles also take the evidence at face value. The studies done by developmental psychologists have an influence that ripples outward and permeates our culture.

During the years I was writing textbooks, I believed the evidence too. But then I looked at it more closely and to my considerable surprise it fell apart in my hands. The evidence developmental psychologists use to support the nurture assumption is not what it appears to be: it does not prove what it appears to prove. And there is a rising tide of evidence against the nurture assumption.

The nurture assumption is not a truism; it is not even a universally acknowledged truth. It is a product of our culture -- a cherished cultural myth. In the remainder of this chapter I will tell you where it came from and how I came to question it.

The Heredity and Environment of the Nurture Assumption

Francis Galton -- Charles Darwin's cousin -- is the one who usually gets the credit for coining the phrase "nature and nurture." Galton probably got the idea from Shakespeare, but Shakespeare didn't originate it either: thirty years before he juxtaposed the two words in The Tempest, a British educator named Richard Mulcaster wrote, "Nature makes the boy toward, nurture sees him forward." Three hundred years later, Galton turned the pairing of the words into a catchphrase. It caught on like a clever advertising slogan and became part of our language.

But the true father of the nurture assumption was Sigmund Freud. It was Freud who constructed, pretty much out of whole cloth, an elaborate scenario in which all the psychological ills of adults could be traced back to things that happened to them when they were quite young and in which their parents were heavily implicated. According to Freudian theory, two parents of opposite sexes cause untold anguish in the young child, simply by being there. The anguish is unavoidable and universal; even the most conscientious parents cannot prevent it, though they can easily make it worse. All little boys have to go through the Oedipal crisis; all little girls go through the reduced-for-quick-sale female version. The mother (but not the father) is also held responsible for two earlier crises: weaning and toilet training.

Freudian theory was quite popular in the first half of the twentieth century; it even worked its way into Dr. Spock's famous book on baby and child care:

Parents can help children through this romantic but jealous stage by gently keeping it clear that the parents do belong to each other, that a boy can't ever have his mother to himself or a girl have a father to herself.

Not surprisingly, it was psychiatrists and clinical psychologists (the kind who see patients and try to help them with their emotional problems) who were most influenced by Freud's writings. However, Freudian theory also had an impact on academic psychologists, the kind who do research and publish the results in professional journals. A few tried to find experimental evidence for various aspects of Freudian theory; these efforts were largely unsuccessful. A greater number were content to drop Freudian buzzwords into their lectures and research papers.

Others reacted by going to the opposite extreme, dumping out the baby with the bathwater. Behaviorism, a school of psychology that was popular in American universities in the 1940s and '50s, was in part a reaction to Freudian theory. The behaviorists rejected almost everything in Freud's philosophy: the sex and the violence, the id and the superego, even the conscious mind itself. Curiously, though, they accepted the basic premise of Freudian theory: that what happens in early childhood -- a time when parents are bound to be involved in whatever is going on -- is crucial. They threw out the script of Freud's psychodrama but retained its cast of characters. The parents still get leading roles, but they no longer play the parts of sex objects and scissor-wielders. Instead, the behaviorists' script turns them into conditioners of responses or dispensers of rewards and punishments.

John B. Watson, the first prominent behaviorist, noticed that real-life parents aren't very systematic in the way they condition their children's responses and offered to demonstrate how to do the job properly. The demonstration would involve rearing twelve young humans under carefully controlled laboratory conditions:

Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I'll guarantee to take any one at random and train him to become any type of specialist I might select -- doctor, lawyer, artist, merchant-chief, and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.

Fortunately for the dozen babies, no one took Watson up on his proposal. To this day, there are probably some aging behaviorists who think he could have pulled it off, if only he had had the funding. But in fact it was an empty boast -- Watson wouldn't have had the foggiest idea of how to fulfill his guarantee. In his book Psychological Care of Infant and Child he had lots of recommendations to parents on how to keep their children from being "spoiled" and how to make them fearless and self-reliant (you leave them alone and avoid showing them affection), but there were no suggestions on how to raise children's IQs by twenty points, which would seem to be an important step toward getting them into medical or law school, in preparation for the first two occupations on Watson's list. Nor were there any guidelines for how to make them choose medicine over law, or vice versa. When it got right down to it, the only thing John Watson had succeeded in doing was to produce conditioned fear of furry animals in an infant named Albert, by making a loud noise whenever little Albert reached for a rabbit. Although this training no doubt discouraged Albert from growing up with the idea of becoming a veterinarian, he still had plenty of other career options to choose from.

A more promising behavioristic approach was that of B. F. Skinner, who talked about reinforcing responses rather than conditioning them. This was a far more useful method because it didn't have to make do with responses the child was born with -- it could create new responses, by reinforcing (with rewards such as food or praise) closer and closer approximations to the desired behavior. In theory, one could produce a doctor by rewarding a kid for bandaging a friend's wounds, a lawyer by rewarding the kid for threatening to sue the manufacturer of the bike the friend fell off. But what about the third occupation on Watson's list, artist? Research done in the 1970s showed that you can get children to paint lots of pictures simply by rewarding them with candy or gold stars for doing so. But the rewards had a curious effect: as soon as they were discontinued, the children stopped painting pictures. They painted fewer pictures, once they were no longer being rewarded, than children who had never gotten any rewards for putting felt-tip pen to paper. Although subsequent studies have shown that it is possible to administer rewards without these negative aftereffects, the results are difficult to predict because they depend on subtle variations in the nature and timing of the reward and on the personality of the reward recipient.

Genius is said to be 99 percent perspiration, 1 percent inspiration. Behaviorism focuses on the perspiration and forgets about the inspiration. Tom Sawyer was a better psychologist than B. F. Skinner: by letting his friends reward him for the privilege of whitewashing the fence, he not only got them to do the work, he got them to like it.

I don't think Watson really wanted a dozen healthy infants to experiment with. I think his request was just a vainglorious way of expressing the basic belief of behaviorism: that children are malleable and that it is their environment, not innate qualities such as talent or temperament, that determines their destiny. The extremist statements were made for their publicity value: Watson was promoting himself for the position of Lord High Environmentalist.

The Art and Science of Studying Children

As an academic specialty, the study of how immature humans develop into adults had a rather late beginning -- around 1890. The early developmentalists were interested in children but didn't pay much attention to their parents. If you look at a developmental psych book written before Freudian theory and behaviorism became popular, you will find little or nothing about parental influences on the development of the child's personality. Florence Goodenough's successful textbook, Developmental Psychology, first published in 1934, has no chapter on parent-child relationships. In her discussion of the causes of juvenile delinquency, Goodenough does talk about the effects of a "bad environment," but she is referring to those parts of a city where the dwellings are "run down and dilapidated" and where there are "many saloons, poolrooms, and gambling-houses."

At about the same time, Winthrop and Luella Kellogg reported the results of their experiment in primate-rearing. They reared a chimpanzee named Gua in their home, side by side with their infant son Donald, and treated them as much alike as possible. The word environment crops up frequently in the Kelloggs' book, but they used it only to distinguish "a civilized environment" or "a human environment" from the jungle or zoo in which Gua would otherwise have been reared. Fine distinctions between one civilized home and another had not yet been pinned to the term environment.

Perhaps the most influential of the early developmentalists was Arnold Gesell. For Gesell as for Goodenough, parents were a taken-for-granted part of the child's environment, anonymous and interchangeable. Children of a given age were pretty much interchangeable as well. Gesell spoke of "your four-year-old" or "your seven-year-old" and gave instructions on how to take care of them, much as a book about cars might have told you how to take care of "Your Ford" or "Your Studebaker." The home was like a garage where the children came home at night and where the anonymous attendants washed them, waxed them, and filled their tanks.

The modern variety of developmental psychology was born in the 1950s, when researchers stopped looking for ways that four-year-olds are similar to other four-year-olds and began to study the ways that they differ from one another. That led to the idea -- and it was a novel idea at the time -- of tracing the differences among the children to differences in the way their parents reared them. The harbinger of this kind of research was a study whose dual ancestry in Freudian psychology and behaviorism was clearly visible. It was designed to test how rewards and punishments dispensed by parents, including their methods of weaning and toilet training, affect their child's personality. In particular, the researchers were interested in aspects of the child's personality that pertained to Freudian concepts such as the development of the superego. One of the researchers was Eleanor Maccoby, now retired from Stanford University after a long and distinguished career. In a recent article, Maccoby described the outcome of this early study:

The results of this body of work were in many respects disappointing. In a study of nearly 400 families, few connections were found between parental child-rearing practices (as reported by parents in detailed interviews) and independent assessments of children's personality characteristics -- so few, indeed, that virtually nothing was published relating the two sets of data. The major yield of the study was a book on child-rearing practices as seen from the perspective of mothers. This book was mainly descriptive and included only very limited tests of the theories that had led to the study.

This inauspicious beginning did not discourage further efforts along the same lines -- on the contrary, it was followed by a deluge of research that has continued to this day. Although the explicit links to Freudian theory and behaviorism were soon dropped, two ideas were retained: the behaviorists' belief that parents influence their children's development by the rewards and punishments they dole out, and the Freudians' belief that parents can mess up their children very badly and often do so.

That parents influence the development of their children was now being taken for granted. The goal of the later generations of researchers was not to find out whether parents influence their children's development but to discover how they influence it. The procedure became standardized: you look at how the parent rears the child, you look at how the child is turning out, you do that for a fair number of parents and children, and then, by putting together all the data and looking for overall trends, you try to show that some aspect of the parent's child-rearing method has had an effect on some characteristic of the child. Your hope is to find a relationship between the parents' behavior and the children's characteristics that is "statistically significant" -- or, to put it in nontechnical terms, publishable.

Although the study described by Eleanor Maccoby failed to find results that were statistically significant, many of the thousands of subsequent studies, cut to the same pattern, were more successful. They did yield significant results and they were published in professional journals such as Child Development and Developmental Psychology; they became part of the mountain of evidence used to support the nurture assumption. Of the others -- the ones that did not yield significant results -- we know very little; most of them probably ended up in landfills. The only reason we know that the first study of this type found "few connections" between the parents' child-rearing practices and the children's personalities is that Dr. Maccoby admitted it in print -- thirty-five years later.

Turning the Wild Baby into a Solid Citizen

Developmentalists who specialize in doing the kind of research I just described are called socialization researchers. Socialization is the process by which a wild baby is turned into a domesticated creature, ready to take its place in the society in which it was reared. Individuals who have been socialized can speak the language spoken by the other members of their society; they behave appropriately, possess the requisite skills, and hold the prevailing beliefs. According to the nurture assumption, socialization is something that parents do to children. Socialization researchers study how the parents do it and how well they do it, as judged by how well the children turn out.

Socialization researchers believe in the nurture assumption. As I said at the beginning, I used to believe in it too. On the basis of that belief, I coauthored three editions of a textbook on child development. I had begun work (without a coauthor this time) on a new development textbook when something happened to make me abandon the project. For years I had been feeling a vague discomfort about the quality of the data in socialization research. For years I had avoided thinking about observations that didn't fit neatly into the story my publishers expected me to tell my readers. One day I suddenly found I no longer believed that story.

Here are three of the observations that bothered me.

First observation. When I was a graduate student I lived in a rooming house in Cambridge, Massachusetts. It was owned by a Russian couple who, along with their three children, occupied the ground floor of the house. The parents spoke Russian to each other and to their children; their English was poor and they spoke it with a thick Russian accent. But the children, who ranged in age from five to nine, spoke perfectly acceptable English with no accent at all -- that is, they had the same Boston-Cambridge accent as the other kids in the neighborhood. They looked like the other kids in the neighborhood, too. There was something foreign-looking about the parents -- I wasn't sure if it was their clothing, their gestures, their facial expressions, or what. But the children didn't look foreign: they looked like ordinary American kids.

It puzzled me. Obviously, babies don't learn to speak on their own; obviously, they learn their language from their parents. But the language those children spoke was not the language they had learned from their parents. Even the five-year-old was a more competent speaker of English than her mother.

Second observation. This one has to do with children reared in England. It came to my attention -- thanks to my weakness for British mystery novels -- that generations of upper-class British males were reared in a way that doesn't make sense in terms of the nurture assumption. The son of wealthy British parents spent most of his first eight years in the company of a nanny, a governess, and perhaps a sibling or two. He spent little time with his mother and even less with his father, whose attitude toward children was typically that they should not be heard and, if possible, not be seen either. At the age of eight the boy was sent off to a boarding school and he remained at school for the next ten years, coming home only for "holidays" (vacations). And yet, when he emerged from Eton or Harrow, he was ready to take his place in the world of British gentlemen. He did not talk and act like his nanny or his governess, or even like his teachers at Eton or Harrow. In his upper-class accent and his upper-class demeanor, he bore a close resemblance to his father -- a father who had had virtually nothing to do with bringing him up.

Third observation. Many developmental psychologists assume that children learn how they are expected to behave by observing and imitating their parents, particularly the parent of the same sex. This assumption, too, is a legacy from Freudian theory. Freud believed that the resolution of the Oedipal or Electra complex leads to identification with the same-sex parent and, consequently, to the formation of the superego. Little children who have not yet made it through the Sturm und Drang of the Oedipal period cannot be expected to behave properly because they have not yet acquired a superego.

Selma Fraiberg, a child psychologist whose books were popular in the 1950s, accepted the Freudian story of socialization. She used the following anecdote to illustrate how children behave during the iffy period when they've learned what they're not supposed to do but can't quite keep themselves from doing it.

Thirty-month-old Julia finds herself alone in the kitchen while her mother is on the telephone. A bowl of eggs is on the table. An urge is experienced by Julia to make scrambled eggs.... When Julia's mother returns to the kitchen, she finds her daughter cheerfully plopping eggs on the linoleum and scolding herself sharply for each plop, "NoNoNo. Mustn't dood it. NoNoNo. Mustn't dood it!"

Fraiberg attributed Julia's lapse to the fact that she had not yet acquired a superego, presumably because she had not yet identified with her mother. But look closely at what Julia was doing when her mother came back and caught her egg-handed: she was making scrambled eggs and she was yelling "NoNoNo." Julia was imitating her mother! And yet Mother was not pleased.

The fact is that children cannot learn how to behave by imitating their parents, because most of the things they see their parents doing -- making messes, bossing other people around, driving cars, lighting matches, coming and going as they please, and lots of other things that look like fun to people who are not allowed to do them -- are prohibited to children. From the child's point of view, socialization in the early years consists mainly of learning that you're not supposed to behave like your parents.

In case you are wondering whether imitating the same-sex parent might work better in a less complex society, the answer is no. In preindustrial societies, the distinction between acceptable adult behavior and acceptable child behavior tends to be even greater than in our own. In village societies in the Polynesian islands, for instance, children are expected to be restrained and submissive with adults and to speak only when spoken to. The adults do not behave this way, either when interacting with their children or when interacting with other adults. Although Polynesian children may learn the art of weaving or fishing by watching their parents, they cannot learn the rules of social behavior that way. In most societies, children who behave like grownups are considered impertinent.

According to the nurture assumption, it is the parents who transmit cultural knowledge (including language) to their children and who prepare them for full membership in the society in which they will spend their adult lives. But the daughter of immigrant parents does not learn the local language and customs from her parents, the son of wealthy British parents sees his parents too rarely to make such a theory plausible, and children in many different cultures are likely to get into trouble if they behave too much like their parents. And yet, all these children somehow do learn to behave the way their society expects them to.

The nurture assumption is based on a particular model of family life: that of a typical middle-class North American or European family. Socialization researchers do not, as a rule, look at families in which the parents cannot speak the local language; they do not study children who go to boarding schools or who are reared by governesses and nannies. Although anthropologists and cross-cultural psychologists have done many studies of childrearing methods in other societies, socialization researchers seldom check to see whether their theories are applicable to children growing up in these other societies.


Of course, some things are true in every society. In every society, babies are born helpless and ignorant and need older people to take care of them. In every society, babies must learn the local language and customs and form working relationships with the other members of their household. They must learn that the world has rules and that they cannot do whatever they feel like doing. This learning has to begin very early, at a time when they are still completely dependent on their adult caregivers.

There is no question that the adult caregivers play an important role in the baby's life. It is from these older people that babies learn their first language, have their first experiences in forming and maintaining relationships, and get their first lessons in following rules. But the socialization researchers go on to draw other conclusions: that what children learn in the early years about relationships and rules sets the pattern for later relationships and later rule-following, and hence determines the entire course of their lives.

I used to think so too. I still believe that children need to learn about relationships and rules in their early years; it is also important that they acquire a language. But I no longer believe that this early learning, which in our society generally takes place within the home, sets the pattern for what is to follow. Although the learning itself serves a purpose, the content of what children learn may be irrelevant to the world outside their home. They may cast it off when they step outside as easily as the dorky sweater their mother made them wear.

Copyright © 1998 by Judith Rich Harris

About The Author

Judith Rich Harris is the author of No Two Alike: Human Nature and Human Individuality . A former writer of college textbooks, Harris is a recipient of a George A. Miller award, given to the author of an outstanding article in psychology. She is an independent investigator and theoretician whose interests include evolutionary psychology, social psychology, developmental psychology, and behavioral genetics.

Product Details

  • Publisher: Free Press (February 24, 2009)
  • Length: 480 pages
  • ISBN13: 9781439101650

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"A graceful, lucid, and utterly persuasive assault on virtually every tenet of child development." -- Malcolm Gladwell, The New Yorker

"Ten years on, this book stands as a landmark in the history of psychology -- and a cracking good read." -- Steven Pinker

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