IQ and Economic Status

I guess Malcolm Gladwell’s new book is coming along nicely, as he’s back blogging intermittently. Today he continues a recent theme of the relationship between race and intelligence quotient, though the post is more about economic status than race. He quotes the psychologist Richard Nisbett:

Most estimates of heritability have been based almost exclusively on studies of middle-class groups. For the poor, a group that includes a substantial proportion of minorities, heritability of I.Q. is very low, in the range of 10 percent to 20 percent.

This is a fascinating point, which I expect man people (me included) wouldn’t have thought to look for. Here’s what it means, to my understanding:

Inheritance is a strong component of IQ for most middle class people (the article suggests 60–80%), indicating that most of us will measure around the same IQ as our parents. There’s still an important percentage that’s going to be determined by our environment, but for the most part we’re going to achieve something close to what our parents did. This is reversed for poorer people. For them the strongest determining factor is environment, with inheritance making up the smaller portion.

This result would seem to imply that we have all the more reason to focus educational support on the disadvantaged areas of society. That’s where we get the most bang for our buck.