Dr. Barres,

Your Nature commentary is rather unrepresentative of the relevant literature. I suggest that you read the references cited in the letter written by Godless Capitalist and myself and the post by our colleague Agnostic.

When the population is sampled from the right extreme of the distribution, sex differences are readily found. This point is even acknowledged by Leahy and Guo in their discussion. Take the Study of Mathematically Precocious Youth, in which the SAT was administered to all students in the participating junior high schools (a sample numbering in the hundreds of thousands).

Top 1 in 1000: A 10-Year Follow-up of the Profoundly Gifted, J.Appl.Psycol. 86, 718-729 (2001).

The above paper analyzed educational outcomes in scorers estimated by normal theory to be among the top 1 in 10,000 in IQ. It should be noted that there is absolutely no question that the SAT is a legitimate proxy for IQ and possesses high validity for the prediction of school achievement, choice of major, and even the probability of obtaining a patent. These generalizations are supported in this very study; this top 1-in-10,000 cohort pursued Ph.D. degress at over 50 times base expectations and boast a long list of accomplishments that includes scientific publications, software innovations, NSF fellowships, a "design for image correlation system for Mars landing program," a physics teaching award, and also several non-scientific distinctions (e.g., a proposal for a voting system in the South African constitution). The items listed in the paper actually underestimate the accomplishments of this cohort (which on average must be under 25 years in age) because some chose not to volunteer biographical information for fear of being identified.

What sex differences are evident when the cutting score is set this extraordinarily deep into the right tail of the ability distribution? A subgroup of these gifted individuals consisting of those with SAT profiles skewed toward math shows a male:female ratio of 169:16. A subgroup with a relatively balanced profile (i.e., more or less equal scores on the SAT-M and SAT-V) shows a male:female ratio of 53:9. A subgroup with a verbal skew shows a ratio of 31:42.

Of the high-math group, what percent of the boys and girls respectively (who, recall, took the SAT as pre-adolescents) majored in math, physical science, engineering, and computer science? 72% and 44%. What about master's degrees? 27% and 25%. That is four women earning master's degrees. Obviously, sample size is inadequate to support rigorous inference. But the reason the sample is so small is that talent searches in junior high schools turn up so few girls scoring >700 on the SAT-M. What about Ph.D.'s? 24% and 12.5%.

Among the balanced group, the breakdown for bachelor's, master's, and doctorates in math, physical science, engineering, is 60% v. 44%, 21% v. zero, and 30% v. zero.

Among the high-verbal group, it's 45% v. 17%, 16% v. 5%, and 10% v. 2%.

These findings (which indicate sex differences in both mental abilities and non-cognitive factors) are quite representative of the literature. In constrast, your characterization of the average phenotypic differences at issue and their impact on real-world outcomes is far out of tune with the massive body of relevant evidence and the judgments of those authorities who are most familiar with it (Camilla Benbow, Diane Halpern, Linda Gottfredson, etc.).

Given the plentiful psychological evidence of which this comment provides a miniscule sample (and the corresponding molecular evidence pointed to by Godless Capitalist), surely any reasonable person must agree that it is at the very least an open question as to whether biologically rooted parameters contribute to the observed sex disparities across scientific disciplines in addition to whatever sociocultural forces may be at play. And a more or less definite answer to this question should be pursued with all possible rigor, as such an answer may contribute to a resolution of an important social issue and to advance our self-understanding as a species. For this reason I strongly urge that you reconsider your dogmatic disparagement of hypotheses invoking biological factors, no matter how distasteful you find them. I believe that impartiality with respect to even the most painful and emotionally laden issues is the only stance reconciliable with a sound scientific conscience.

Regards,
Darth Quixote