ommenting 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."
The topic of race differences in IQ occupies only a fraction of The Bell Curve and is not at all essential to its main argument. All the socially important correlates of IQ are demonstrated in the white population sample. But the mass media have pounced exclusively on the race issue and, with a few notable exceptions, by and large have gone into paroxysms of denial, trashing the factual basis of The Bell Curve in every conceivable way, as if obeying a categorical imperative to inoculate the public against it.
Although social problems involving race are conspicuously in the news these days, too few journalists are willing or able to discuss rationally certain possible causes. The authors' crime, apparently, is that they do exactly this, arguing with impressive evidence that the implications of IQ variance in American society can't be excluded from a realistic diagnosis of its social problems.
The media's spectacular denial probably arises from the juxtaposition of the book's demonstrations; first, that what is termed "social pathology"--delinquency, crime, drug abuse, illegitimacy, child neglect, permanent welfare dependency--is disproportionately concentrated (for whites and blacks alike) in the segment of the population with IQs below 75; and second, that at least one-fourth of the black population (compared to one-twentieth of the white population) falls below that critical IQ point in the bell curve. Because the smaller percentage of white persons with IQs below 75 are fairly well scattered throughout the population, many are guided, helped, and protected by their abler families, friends, and neighbors, whose IQs average closer to 100. Relatively few are liable to be concentrated in the poor neighborhoods and housing projects that harbor the "critical mass" of very low IQs which generates more than its fair share of social pathology. The "critical mass" effect exists mostly in the inner city, which has been largely abandoned by whites. Of course thinking citizens are troubled. Thinking about possible constructive remedies strains one's wisdom.
But can any good for anyone result from sweeping the problem under the rug? Shouldn't it be exposed to earnest, fair-minded public discussion? Our only real fear, I think, should be that such discussion might not happen. Consideration of the book's actual content is being displaced by the rhetoric of denial: name calling ("neo-nazi," "pseudo-scientific," "racism," "quackery"), sidertracks ("but does IQ really measure intelligence?"), non-sequitures ("specific genes for IQ have not been identified, so we can claim nothing about its heritability"), red herrings ("Hitler misused genetics"), ad hominem attacks ("written in a conservative think tank"), falsehoods ("all the tests are biased"), hyperbole ("throwing gasoline on a fire"), and insults ("dishonest," "creepy," "indecent," "ugly").
The remedy for this obfuscation is simply to read the book itself. We should hope that President Clinton will do so before he speaks out on the subject again, or at least ask his science advisor's opinion of whether it is a serious work on important issues by qualified scholars. It would clear the air if the President asked the National Academy of Sciences to appoint a panel of experts to evaluate the factual claims of The Bell Curve and report its conclusions to the public. There is a precedent for such an action. Following the publication of my book Bias in Mental Testing, the NAS convened a panel of experts to examine the body of research it covered and issued a two-volume report confirming my main conclusions. A similar detailed examination of The Bell Curve seems warranted by the public's evident concern with the empirical substance of the argument and its meaning for the nation's future.