The recent debate between James Flynn (of the Flynn Effect) and Charles Murray (of The Bell Curve) has lead to a flurry of posts on various blogs. For a summary, read here. The event, papers, and the video are here.
There is no doubt that there is a gap in IQ scores between black and white Americans. There is no doubt that IQ scores have improved over time, although they may now no longer do so. For example, there are indications that this trend has been arrested or even reversed in Norway and Denmark.
The question is, is the IQ gap between blacks and whites closing? If not, why not? Flynn blames black teenage culture for part of the problem. A earlier cultural explanation was provided by Lee Willerman in 1974 (his work has been quoted e.g. by Orlando Patterson and Richard Nisbett). Willerman showed that there was a difference in IQ between mixed race children who had a black mother, and those who had a white mother. You would expect children of mixed parentage to have the same average IQ regardless of which parent was black. If mothers are more important than fathers to the intellectual socialization of their children, and if the socialization practices of whites favor the acquisition of skills that result in high IQ scores, children of white mothers and black fathers should score higher than children of black mothers and white fathers. In fact, children of white mothers and black fathers have a 9 point IQ advantage over those with black mothers and white fathers. Unless extreme selection factors are at work, this result suggests that much of the black/white IQ gap is environmental.
I don’t know if Willerman’s study has been replicated, but it would certainly be interesting to see a more recent study.