In 1998 Judith Rich Harris, an independent researcher and textbook author, published The Nurture Assumption: Why Children Turn Out The Way They Do. The book provocatively argued that parents matter much less, at least when it comes to determining the behavior of their children, than is typically assumed. Instead, Harris argued that a child’s peer group is far more important. The Nurture Assumption has recently been reissued in an expanded and revised form. Mind Matters editor Jonah Lehrer chats with Harris about her critics, the evolution of her ideas and why teachers can be more important than parents.

LEHRER: Freud famously blamed the problems of the child on the parents. (He was especially hard on mothers.) In The Nurture Assumption, an influential work that was published 10 years ago, you argued that parents are mostly innocent and that peers play a much more influential role. What led you to write the book?

HARRIS: It wasn’t just Freud! Psychologists of all persuasions, even behaviorists such as B. F. Skinner, thought the parents were responsible, one way or the other, for whatever went wrong with a child. One of my purposes in writing the book was to reassure parents. I wanted them to know that parenting didn’t have to be such a difficult, anxiety-producing job, that there are many different ways to rear a child, and no convincing evidence that one way produces better results than another.

But my primary motive was scientific. During the years I spent writing child development textbooks for college students, I never questioned the belief that parents have a good deal of power to shape the personalities of their children. (This is the belief I now call the “nurture assumption.”) When I finally began to have doubts and looked more closely at the evidence, I was appalled. Most of the research is so deeply flawed that it is meaningless. And studies using more rigorous methods produce results that do not support the assumption.

LEHRER: How did the field react?

HARRIS: The initial reaction was far off the mark. Professors of psychology were asked to give their opinion of the book before they’d had a chance to read it, so their comments were based on what they had heard about it. Many of them responded by saying that, “Harris has ignored a great deal of evidence.” But when pressed to specify the evidence I had ignored, they’d name the very same kinds of studies I had mercilessly dissected in the book. Or they’d tell the journalist about a study that hadn’t yet been published but that, when published, would prove that Harris was wrong. My attempt to track down those unpublished studies is described in my second book, No Two Alike.

As time went on, the professors calmed down. Some of them began to listen to what I was saying, perhaps because I was also publishing articles in academic journals. My work is now cited in many psychology textbooks and assigned in college courses. Of course, most developmental psychologists still don’t agree with me, but at least they’re acknowledging that there’s another point of view.

There has also been some improvement in research methodology, due not to my nagging but to a greater awareness of genetic influences on personality. It’s no longer enough to show, for example, that parents who are conscientious about childrearing tend to have children who are conscientious about their schoolwork. Is this correlation due to what the children learned from their parents or to the genes they inherited from them? Studies using the proper controls consistently favor the second explanation. In fact, personality resemblances between biological relatives are due almost entirely to heredity, rather than environment. Adopted children don’t resemble their adoptive parents in personality. I’m not particularly interested in genetic effects, but the point is that they have to be taken into account. Unless we know what the child brings to the environment, we can’t figure out what effect the environment has on the child.



LEHRER: Why do you think this is such a controversial idea? In other words, why are we so convinced that parents must matter?

HARRIS: It’s part of the culture. Questioning a cherished cultural myth is always risky. What most people don’t realize is that different cultures have different myths about the role of parents. The belief that parents have a great deal of power to determine how their children will turn out is actually a rather new idea. Not until the middle of the last century did ordinary parents start believing it. I was born in 1938, before the cultural change, and parenting had a very different job description back then. Parents didn’t feel they had to sacrifice their own convenience and comfort in order to gratify the desires of their children. They didn’t worry about boosting the self-esteem of their children. In fact, they often felt that too much attention and praise might spoil them and make them conceited. Physical punishment was used routinely for infractions of household rules. Fathers provided little or no child care; their chief role at home was to administer discipline.

All these things have changed dramatically in the past 70 years, but the changes haven’t had the expected effects. People are the same as ever. Despite the reduction in physical punishment, today’s adults are no less aggressive than their grandparents were. Despite the increase in praise and physical affection, they are not happier or more self-confident or in better mental health. It’s an interesting way to test a theory of child development: persuade millions of parents to rear their children in accordance with the theory, and then sit back and watch the results come in. Well, the results are in and they don’t support the theory!

LEHRER: Have your ideas changed at all since writing the book?

HARRIS: They’ve expanded rather than changed. I’ve filled in some holes. A few years after the first edition of The Nurture Assumption was published, I realized that the theory proposed in that book, Group Socialization Theory, was incomplete. It does a good job of explaining socialization the way children acquire the behaviors, skills and attitudes approved by their culture but a poor job of explaining personality development. As children become socialized, their behavior becomes more similar to that of their same-sex peers. But differences in personality don’t go away—if anything, they widen. Group Socialization Theory doesn’t explain, for example, why identical twins have different personalities, even if they’re reared in the same home and belong to the same peer group. That’s the puzzle I tackled in No Two Alike. The expanded version of the theory is based on the idea that the human mind is modular and that it consists of a number of components, each designed by evolution to perform a specific job, and that three different mental modules are involved in social development. The first deals with relationships, including parent-child relationships. The second handles socialization. The third enables children to work out a successful strategy for competing with their peers, by figuring out what they are good at.

LEHRER: You emphasize the importance of teachers in shaping a child's development. How can we apply this new theory of child development to public policy?

HARRIS: I’ve put together a lot of evidence showing that children learn at home how to behave at home (that’s where parents do have power!), and they learn outside the home how to behave outside the home. So if you want to improve the way children behave in school—for instance, by making them more diligent and less disruptive in the classroom—then improving their home environment is not the way to do it. What you need is a school-based intervention. That’s where teachers have power. A talented teacher can influence a whole group of kids.

The teacher’s biggest challenge is to keep this group of kids from splitting up into two opposing factions: one pro-school and pro-learning, the other anti-school and anti-learning. When that happens, the differences between the groups widen: the pro-school group does well, but the anti-school group falls further and further behind. A classroom with 40 kids is more likely to split up into opposing groups than one with 20, which may explain why students tend to do better in smaller classes. But regardless of class size, some teachers have a knack for keeping their classrooms united. Teachers in Asian countries seem to be better at this than Americans, and I suspect this is one of the reasons why Asian kids learn more in school. No doubt there’s a difference in cultures, but maybe we could study how they do it and apply their methods here.

The tendency of kids to split up spontaneously into subgroups also explains the uneven success rate of programs that put children from disadvantaged homes into private or parochial schools. The success of these programs hinges on numbers. If a classroom contains one or two kids who come from a different background, they assimilate and take on the behaviors and attitudes of the others. But if there are five or six, they form a group of their own and retain the behaviors and attitudes they came in with.

President Obama has promised to restore science to its rightful place. I hope he realizes that its rightful place doesn’t have to be a laboratory. It can also be a school classroom.

Are you a scientist? Have you recently read a peer-reviewed paper that you want to write about? Then contact Mind Matters editor Jonah Lehrer, the science writer behind the blog The Frontal Cortex and the book Proust Was a Neuroscientist. His latest book is How We Decide.