Bias in Mental Testing
There are many styles of retreat in the face of failure. As a first and most forthright strategy, one can simply be humble and contrite. Clarence Darrow once stated that if God really existed after all, and if he were, following his death, arraigned before God as judge with the twelves apostles in the jury box, he would simply step up to the bench, bow low, and say: “Gentlemen, I was wrong.” In a second, intermediate strategy—the stiff upper lip—one looks upon the bright side (or sliver) of admitted adversity. When Robert FitzRoy, Darwin’s captain on the Beagle, learned that Jemmy Button, the Fuegian native he had trained in English ways, had “reverted” completely to old habits within months of his return, FitzRoy took refuge in the thought that “a ship-wrecked seaman may hereafter receive help and kind treatment from Jemmy Button’s children; prompted, as they can hardly fail to be, by the traditions they will have heard of men of other lands.” As a third tactic, one proclaims triumph and punts hard. I remember Senator Aiken’s brilliant solution to the morass of Vietnam—that we should simply declare victory and get out.
Arthur Jensen has published an 800-page manifesto embodying this third strategy. To understand why it represents a retreat—and a failed retreat at that—we must review the history of its genesis. In his notorious article of 1969, the founding document of “Jensenism” as a public issue, Jensen maintained that compensatory education must fail because the black children that it attempted to aid were, on average, genetically inferior to white children in intelligence. He based his claim on a strong form of genetic argument: the heritability of IQ, he maintained, had been adequately estimated at about 0.8 among whites; therefore, the 15 point average difference in IQ scores between blacks and whites must be largely innate in origin.
The intervening decade between this article and the present book has not been kind to Arthur Jensen. First of all, the estimate of heritability, depending so heavily on Sir Cyril Burt’s faked data, is clearly too high. Second, and more important, the value of heritability within either the white or the black population carries no implication whatever about the causes for different average values of IQ between the two populations. (A group of very short people may have heritabilities for height well above 0.9, but still owe their relative stature entirely to poor nutrition.) Within and between group variation are entirely different phenomena; this is a lesson taught early in any basic genetics course. Jensen’s conflation of these two concepts marked his fundamental error.
I assume that Jensen now understands where he went seriously astray. The present book bypasses the issue of heritability entirely. In dismissing this previous bulwark of his system in just two paragraphs, Jensen simply states that the matter is too complicated for treatment here, though he relishes some of the most arcane and complex …
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Jensen and Bias: An Exchange October 23, 1980