On November 28 the American Enterprise Institute held a symposium on the persistent gap between the average IQ test scores of black and non-Hispanic white Americans. The question: Is the gap closing? The presenters at AEI were James Flynn, a philosopher who taught at the University of Otago in New Zealand, and Charles Murray, a scholar at AEI and the co-author of The Bell Curve.
Flynn is famous for having discovered in the 1980s that average IQs in many countries have been drifting upward at about 3 points per decade over the past couple of generations. In fact, the average has risen by an astonishing 15 points in the last 50 years in the United States. In other words, a person with an average IQ of 100 today would score 115 on a 1950s IQ test.
Flynn believes that the data show that the black/white gap is closing—that the average IQ scores of black Americans are rising faster than those of whites. And he began his talk at AEI by describing a study done by a German psychometrician who tested the IQs of 170 white and 69 half-black children left behind in Germany by American GIs. The average score for the white kids was 97 and 96.5 for the half-black kids. Flynn pointed out that the black German kids would probably have had a harder time in German society, yet they scored almost identically to their white counterparts. If the Eyferth study is right, the differences in IQ cannot be attributed to genetics.
Nevertheless, Flynn noted, in the US the tendency is for the black/white IQ score gap to widen with age. According to Flynn, the average IQ for black four-year olds is 95.4, which drops to 89.4 at age 14 and widens further to 83.4 by age 24. Flynn dismissed the argument that pregnant black women were on average less health conscious than white women. Flynn said that when he looked at the data he could not find evidence that black women smoke or drink more than white women, though black women do tend gain a bit less weight while pregnant which might indicate under-nutrition. Flynn further observed that blacks generally do worse on vocabulary tests and he suggested that a cultural difference might explain it. The children of professionals hear about 2500 different words in a day whereas the children of welfare mothers hear about 600 different words every day. Finally, Flynn believes that the black adolescent subculture that devalues education is largely responsible for widening the IQ gap. “It is more probable than not that the black/white IQ gap results from environmental factors,” he declared.
When his turn came, Charles Murray noted that the black/white IQ score gap did close somewhat during the 20th century, but that the data show that the narrowing stalled sometime in the 1970s. “The remaining gap will be with us indefinitely,” he concluded. Murray argued that a lot the earlier narrowing of the gap occurred as more educational and job opportunities opened and better health and nutrition became available for blacks as state-enforced segregation ended. Once a “merely adequate” environment is provided, there are diminishing marginal returns for increasing IQ scores. He noted that the programs established by the No Child Left Behind Act have had almost no effect on the black/white educational achievement gap. Murray also observed that the German study of children born to American GIs given such prominence because its findings conform to the beliefs and hopes of those who think that environmental influences are solely responsible for the black/white gap in average IQ scores. However, it is contrary to the vast majority of the literature on racial differences in IQ test scores.
Murray argued that general intelligence, so-called "g," a general factor that governs performance on all cognitive tasks, is highly heritable. He noted that g has a biological background in the brain. He cited differences in glucose metabolism, reaction times, and the volumes of specific grey matter in prefrontal cortices.
Both Flynn and Murray agree that a gap between average black and white scores on IQ tests remains, but since they are both looking at the same information, why don’t they agree on whether the gap is closing or not? The difference turns on how they slice the data. Murray prefers to look at test scores by birth cohorts, e.g., how the scores of white and black 18-year olds stack up to one another. Those data show no closing of the gap on tests administered since the late 1970s. It remains at about 15 IQ points. Flynn looks at test scores in the year they are administered without taking account of differences in age, e.g., how blacks and whites of every age who took in the test in 1985 compare. Flynn found that the black/white IQ score gap narrowed by 5.67 points between 1972 and 2002. Thus the IQ gap has fallen from 15 points to about 10 ten points. Flynn and Murray agree that the debate over how best to analyze the data is not settled.