Nature vs. Nurture

Dennis Mangan has a post about a recent book by Judith Rich Harris that claims that parental care has no effect on a child's behavior:

The developmentalists found that the children's behavior was correlated with the parents' behavior and attributed the correlation to the effects of the home environment. Though they realized that heredity might account for some of the correlation, they never considered the possibility that heredity might account for all of it. But that is exactly how it turned out. Once the effects of genetic similarities were estimated and skimmed off, the correlation declined to zero. The putative effects of the home environment disappeared.

I can't entirely buy that. Taken literally, it would mean that you can beat up your children, sexually molest them, let them be raised by wolves, and it doesn't change a thing.

I think a far more likely explanation is the "weakest link" one: nurture and nature each determine a level of behavior for your child (I'm pretending that behavior can be looked at as a linear quantity from "good" to "bad") and whichever level is worse, is where your child is. Put another way, parental care cannot overcome a child's genetics, but it can harm a child. The reason why parnetal care does not seem to have an effect is that the parents are almost always equal to or better than the genetics; when the parent is biological, they tend to be equal to; when adoptive, better than; because adoptive parents tend to be screened and because people who have to give their babies up for adoption are probably disproportionately people with genetic disadvantages.

I think that this would fit the facts and also seem more reasonable to me; it does not strike me as odd that a child whose parents are from a disadvantaged ackground might not be "fixed" by putting him with a well-behaved upper middle-class family. It beggars belief that the child of a well-behaved upper middle-class family would not be damaged by letting a couple who are abusive to him and who run a crackhouse adopt him.

That is all.