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HERITABILITY OF I.Q.

THE MAIL

To the Editors of The Crimson:

Allow me to correct some of the impressions that may have been left by Jeffrey Dunn's piece ("Layzer Wants SAT's Replaced by Specific Competence Tests," April 9). My article in the March 29 issue of Science, referred to in the opening paragraph of The Crimson story, neither mentions SAT's nor does it have any direct implications concerning their use by college admissions officers. Since SAT scores are good statistical predictors of scholastic performance in the freshman year, they are clearly relevant to the selection process. I agree with Henry Dyer, a recently retired vice-president of Educational Testing Service, that tests of specific competence are more valuable than IQ tests (e.g., the Stanford-Binet and the Wechsler), which are intended to assess hypothesized innate qualities underlying cognitive performance. (Belief in the validity of such assessments rests on pre-scientific views concerning human intelligence and its development.) I also agree with Mr. Dyer's view that tests of specific kinds of competence can and should be used to assess the effectiveness of teaching methods and curricula. None of these ideas is in the least original or newsworthy; I would be surprised to find an admissions officer or educational psychologist who disagreed with them.

My article in Science addressed a different set of issues: the mathematical and biological underpinnings of the theory that geneticists use to estimate heritabilities of phenotypic traits, and the applicability of that theory to IQ test scores. One frequently reads (for example, in letters to The Crimson) that there is a consensus among quantitative geneticists that the heritability of IQ is in the range .6 to .8. This conclusion, if true, would mean that most of the IQ variation in the white U.S. population results from genetic differences. My Science article argued that "heritability of IQ" is a strictly meaningless concept, for two main reasons. First, IQ scores are not phenotypic measurements: they contain uncontrollable systematic errors; and, though numerical, they are not quantitative. Second, even if appropriate measurements of cognitive skills were available, one could not meaningfully apply conventional heritability analysis to them. The reason is that certain mathematical conditions needed for the application of conventional heritability analysis are almost certainly not satisfied for important behavioral traits in natural human populations. Thus arguments about the value of IQ heritability are a little like arguments about the number of angels that can dance on the head of a pin.

Finally, the Science article emphasized the importance of recent studies showing that appropriate educational and social programs can greatly accelerate the cognitive development of children from poverty backgrounds. The evidence already accumulated is extremely encouraging, and flatly contradicts the doctrine that IQ measures an innate capacity and that low IQ indicates an inability to acquire "higher" cognitive skills. David Layzer

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