An interesting interview 1999 at Edge reloaded: Children don’t do things half way: children don’t compromise with Judith Rich Harris
How the parents rear the child has no long-term effects on the child’s personality, intelligence, or mental health. […] The trouble is, the evidence is ambiguous. It’s clear that children resemble their biological parents; what isn’t clear is why. Is it the environment the parents provided, or is it the genes they provided? Just knowing there’s a correlation isn’t enough—we have to tease apart the effects of the genes from the effects of the home environment. One way to do it is by looking at adopted kids. And what we find is that the correlation disappears. The adopted child reared in a let’s-read-a book-together home ends up no smarter, on the average, than the one reared in a don’t-bother-me-I’m-watching-TV home. […] In fact, for personality (which is what I’m mainly interested in), only about half the variation from one person to another can be attributed to the genes. More precisely, about half the reliable variance in measured personality characteristics—the variance that remains after measurement error is subtracted—can be attributed to differences in genes. […] They still haven’t acknowledged the fact that whatever genetic predispositions the children have, there’s a good chance the parents have them too. […] In study after study, was that the environment shared by two kids reared in the same home could account for no more than 5 percent of the variance in personality characteristics. […] Well, the way children behave outside their parents’ home is certainly more lasting, because that’s where they’re going to spend their adult lives. […] the impetus comes from the child doing the conforming, not from the group. Tailoring your behavior to that of the other members of your group is something that people of all ages do automatically, usually without even realizing that they’re doing it.