To the Editors of The Crimson:

One reason I try to avoid arguing with the local SDS is that they appear to be uneducable on the subject of I.Q. Mrs. Kilbreth (a former student in Social Sciences 15) has produced a case in point, which The Crimson has obligingly published. (Would The Crimson be interested in a rebuttal from a student who learned something about I.Q. in Social Sciences 15?) Most of her errors -- and they are the familiar errors made by people who find the facts unsettling -- are dealt with specifically in my book I.Q. in the Meritocracy, and in the large scholarly literature cited therein.

I trust readers will forgive me if I do not try to rewrite my book each time someone displays the standard confusions and errors. Here, in any event, are some assertions of my own, which my book attempts to support by evidence

1) The high estimates of the heritability of I.Q. do not rest entirely on the famous 122 twin cases. (Incidentally, no one has yet shown anything seriously wrong with those data). There are, in addition, literally tens of thousands of correlational pairs: siblings, parents and children, natural or foster parents and children, fraternal twins compared to identical twins, and so on and on, since the first decade of the century. The overwhelming mass of evidence implies a heritability for I.Q. of 60 per cent or over. The 80 per cent figure turns up fairly often, but it is not necessary to my argument that it be so high that we should know it so exactly.

2) I.Q. tests do not just measure "class background." If they did, then they would show a low, instead of a high, heritability. As any student of Social Sciences 15 (at least during my two-year stint) should have learned, a trait that has high heritability is relatively unaffected by existing environmental variables.

3) Educational achievement is the best known predictor of occupational standing, even according to Messrs. Bowles and Gintis (with whom I disagree on other matters). Moreover, I.Q. is the best known predictor of educational achievement. Finally, genetic factors are the main known determiners of I.Q. That is the chain of findings that I have tried to bring to public attention. Contrary to Mrs. Kilbreth's impression, I have yet to see facts to the contrary. There are, to be sure, differences among scholars on the empirical details, which I hope I have fairly reflected in my book.

4) I do not advocate social policies. Instead, I try to show the consequences of one social policy or another, given the facts.

5) Finally, I have never said that Mrs. Kilbreth has not read my writings on I.Q. Having read her article, I would, however, say that it is the generous assumption to suppose that she has not. R.J. Herrnstein   Professor of Psychology