Why home doesn't matter

The BBC series "Child of Our Time" assumes that studying children with their parents will help us understand how their personalities develop. But this is a mistake: parents influence their children mainly by passing on their genes. The biggest environmental influences on personality are those that occur outside the home
During much of the 20th century, it was considered impolite and unscientific to say that genes play any role in determining people's personalities, talents or intelligence. But we're in the 21st century now, the era of the genome. So when Robert Winston informs us, at the opening of each episode of the BBC1 documentary series Child of Our Time, that we're going to "find out what makes us who we are," we know he's going to say that people are the way they are partly for genetic reasons. (In case you've missed it, Child of Our Time is a project tracking the lives of 25 children for their first 20 years, returning to them each year to assess their progress.
Child of Our Time is itself a sign of scientific progress because of its enlightened approach to the genome. Nevertheless, the series is scientifically misleading. Simply depicting the lives of 25 children, or sprinkling little "experiments" here and there throughout the programmes, sheds no light on the nature vs nurture question. Psychologists studied child development in this way for the better part of a century and learned remarkably little. Observing children at home or in school, individually or in groups, is not the way to answer the question of why they turn out the way they do.
The problem is that most children are reared by their biological parents, so the parents provide both the genes and the home environment. The effects of the genes are therefore impossible to separate from the effects of the environment. Young Johnny has a strong drive to succeed? Well, that's not surprising—so does his father! But does Johnny's drive to succeed come from lessons learned from his father, from genes inherited from his father, or from some combination of the two? Most 20th-century developmental psychologists assumed it was mainly Johnny's experiences at home that made him who he is today. Even those who admitted that genes may play a role continued to feel that the child's environment—by which they meant the home environment—was of greater importance.( more from prospect )
Judith Rich Harris is a psychologist and author of No Two Alike: Human Nature and Human Individuality (WW Norton)