Arthur R. Jensen, National Review, December 5, 1994.
Commenting not as an advocate but as an expert witness, I can say that The Bell Curve is correct in all its essential facts. The graphically presented analyses of fresh data (from the National Longitudinal Survey of Youth) are consistent with the preponderance of past studies. Nowadays the factual basis of The Bell Curve is scarcely debated by the experts, who regard it as mainstream knowledge. The most well-established facts: Individual differences in general cognitive ability are reliably measured by IQ tests. IQ is strongly related, probably more than any other single measurable trait, to many important educational, occupational, economic, and social variables. (Not mentioned in the book is that IQ is also correlated with a number of variables of the brain, including its size, electrical potentials, and rate of glucose metabolism during cognitive activity.) Individual differences in adult IQ are largely genetic, with a heritability of about 70 per cent. So far, attempts to raise IQ by educational or psychological means have failed to show appreciable lasting effects on cognitive ability and scholastic achievement. The IQ distribution in two population groups socially recognized as “black” and “white” is represented by two largely overlapping bell curves with their means separated by about 15 points, a difference not due to test bias. IQ has the same meaning and practical predictive validity for both groups. Tests do not create differences; they merely reflect them.
The conjuction of these facts is a troubling picture to most people. And rightly so. The book’s penultimate chapter (“The Way We Are Headed”), in the light of the chapters that precede it, probably leaves most readers depressed and disturbed, and it should. I, for one, am not all that comforted by the final chapter’s remedial recommendations for public policy, entirely sensible though they may be. In the present climate, they have a slim chance of being realized. Yet one hates to believe there may be no morally acceptable, feasible, and effective way to mitigate the most undesirable social consequences of the increasing IQ stratification of the nation’s population. The phenomenon itself is almost inevitable in a technological civilization. It is simply more salient when there are large subpopulations that differ in mean IQ. The “custodial society,” which the authors portray as the worst scenario for public policy (and which their recommendations are intended to prevent), is hardly an agreeable resolution to most Americans. Yet at present it seems that is “the way we are headed.”