More thoughts on Eric Turkheimer's research:
The more I think about it, the more convinced I am Turkheimer's work is one of the keys to unraveling the Race-IQ debate. His argument goes something like this:
Right now, there are two conflicting pieces of evidence, each of which is seized upon by each side in the debate. On the one hand, there are twin studies. You look at twins, raised in very different adoptive families, and you find that their IQs are very similar. That suggests IQ is largely heritable, and that environment plays only a modest role.
On the other hand, there are studies showing that if a child of a very poor family, adopted at birth into a wealthy family, will have a much higher IQ than his or her siblings, or his or her parents, who remain in poverty.
This is, obviously, not a trivial disagreement. Someone like Charles Murray, who takes the former position, uses it as explanation for why he think social programs--like Head Start--are a waste of time and money. It is also why he thinks that the gap that presently exists between white and black average IQ scores will likely persist, regardless of what kind of steps we take as a society. Liberals, meanwhile, use the latter evidence to justify the idea of an aggressive social policy.
So who's right? Turkkeimer would say, both sides are.
He used a very large data set--the National Collaborative Perinatal Project--and found that the relationship between socio-economic status and IQ was non-linear. Children moving from poverty to the middle class see their IQ's jump: IQ at that end of the socio-economic scale is highly sensitive to environmental improvements. But the kinds of twins studies usually relied upon by IQ fundamentalists and that yield such high genetic effects, are much more likely to involve comparisons among middle and upper middle class environments--and that end of the scale, Turkheimer's data suggests, environment doesn't play a big role.
In other words, the lawyer who plays Mozart in the crib for his daughter, in order to raise her IQ, is wasting his time. But dramatically increasing the educational resources available to inner city kids makes a lot of sense.
This, I think, helps to clarify a lot of what drives so many of us crazy about Charles Murray and his ilk. We're not disputing the importance of IQ. And we're not disputing that genes play a huge role in determining IQ. We're just saying that it's hopelessly naive to assume that the same rules apply to suburban, middle-class whites as apply to, say, urban, inner-city black families.