In this Editorial we correct the false claim that g loadings and inbreeding depression scores correlate with the secular gains in IQ. This claim has been used to render the logic of heritable g a "red herring" and an "absurdity" as an explanation of Black-White differences because secular gains are environmental in origin. In point of fact, while g loadings and inbreeding depression scores on the 11 subtests of the Wechsler Intelligence Scale for Children correlate significantly positively with Black-White differences (0.61 and 0.48, Pb0.001), they correlate significantly negatively (or not at all) with the secular gains (mean r=-0.33, Pb0.001; and 0.13, ns, respectively). Moreover, heritabilities calculated from twins also correlate with the g loadings (r=0.99, Pb0.001 for the estimated true correlation), providing biological evidence for a true genetic g, as opposed to a mere statistical g. While the secular gains are on g-loaded tests (such as the Wechsler), they are negatively correlated with the most g-loaded components of those tests. Also, the tests lose their g loadedness over time with training, retesting, and familiarity. In an analysis of mathematics and reading scores from tests such as the NAEP and Coleman Report over the last 54 years, we show that there has been no narrowing of the gap in either IQ scores or in educational achievement. From 1954 to 2008, Black 17-year-olds have consistently scored at about the level of White 14-year-olds, yielding IQ equivalents of 85 for 1954, 82 for 1965, 70 for 1975, and 81 for 2008. We conclude that predictions about the Black-White IQ gap narrowing as a result of the secular rise are unsupported. The (mostly heritable) cause of the one is not the (mostly environmental) cause of the other. The Flynn Effect (the secular rise in IQ) is not a Jensen Effect (because it does not occur on g).Flynn responds:
The ranking of Wechsler subtests in terms of their g loadings is equivalent to ranking them in terms of the cognitive complexity of the tasks measured. Lower performing groups do not always fall behind higher performing groups the more complex the task. But that is the general rule, no matter whether the cause of the lower performance is genetic or environmental. Complex tasks tend to be more affected by genetic differences in inherited traits, have higher heritability, and be more sensitive to inbreeding depression. Therefore, the method of correlated vectors sheds no light on the race and IQ debate. It is irrelevant that black/white score differences on Wechsler subtests rise as their g loading, heritability, and inbreeding sensitivity rise.Here's my review of Flynn's book on the Flynn Effect, which Flynn thought did a pretty good job of making Flynn's thinking accessible.
Flynn always uses basketball analogies in arguing against the necessity of genetic causes in IQ differences, but that obviously raises issues unhelpful to Flynn's cause. Other sports can provide better examples. For example, in golf, it's widely acknowledged that the hardest clubs to hit well are the long irons. And the long irons are precisely where Jack Nicklaus and Tiger Woods, the two greatest golfers, distanced themselves from the field, by reaching par-5 greens accurately in two to give themselves putts for eagles. Nature or nurture? Well, certainly a lot of both, but the exact balance is hard to say. Flynn sums up that he doesn't believe either his own Flynn Effect or Jensen's g-factor analysis is very persuasive in determining the nature-nurture breakdown in the racial IQ gap:
American blacks are not in a time warp so that the environmental causes of their IQ gap with whites are identical to the environmental causes of the IQ gap between the generations. The race and IQ debate should focus on testing the relevant environmental hypotheses. The Flynn Effect is no shortcut; correlations offered by Rushton and Jensen are no shortcut. There are no shortcuts at all.Flynn has a Blind Side / Stolen Generation-style theory that black culture doesn't lead to strong cognitive demands, although he's leery about spelling out the policy implications, although you can see it made a little more explicit in the increasing enthusiasm in, say, the New York Times Sunday Magazine for taking black children away from their mothers as many hours per day as possible and turning them over to Ivy League Teach for America workers to raise in a white-run world. Maybe it will work, I dunno. Yet, I suspect we'll just be seeing in a few decades a replay of the Australian experience, with whites issuing an apology to blacks for the "Borrowed Generation."