Gender Differences in Scientific Achievement

Larry Summers, the president of Harvard, stirred up a hornet's nest when, at a recent conference on the underrepresentation of women and members of minority groups in science and engineering, he suggested the following two possible reasons why women are underrepresented. First, women's math and science aptitude test scores exhibit less variance than men's and this difference may have a biological basis. Second, women are on average unwilling to make the same sacrifice of time to career that men are willing to do. (A third reason, he suggested, might be discrimination against women.) Conference. (For an interesting discussion of the issues, see Saletan.) I want to consider whether there is any merit to his suggestions'but also whether he should have raised the issue at all, given his position as the president of the nation's best-known university, and whether, having done so and been criticized, he should have apologized, as he did; he said that he had been "wrong to have spoken in a way that has resulted in an unintended signal of discouragement to talented girls and women," although he did not repudiate the content of his remarks. Summers.

Were Summers an expert on the reasons for gender-related occupational patterns, and as a result had special insight into the issue of women's lack of proportional representation in science careers, there might have been a real cost in his failing to speak to the issue. However, since he is not an expert in this area, there would have been no great loss to human knowledge had he kept silent and let the experts engage with the issue. Although it is a highly sensitive issue, it is not'unlike the issue of racial differences'so hot a topic that no reputable academic dares investigate it.

So the benefit of Summers's speaking out was small. The cost would have been small, too'were he not the highly visible president of the nation's most famous university. For as a practical matter, chief executive officers do not enjoy freedom of speech. A CEO is the fiduciary of his organization, and his duty is to speak publicly only in ways that are helpful to the organization. Not that he should lie; but he must avoid discussing matters as to which his honestly stated views would harm the organization. (Judges also lack complete freedom of speech; as I mentioned in our introductory blog posting, I am not permitted to comment publicly on any pending or impending court case.) Summers must think that his remarks did harm the university, as otherwise he would not have apologized'for he apologized not for what he said, but for saying it.

A university president might make provocative remarks because he wanted to change his university in some way, for example by encouraging greater intellectual diversity, or because he wanted to signal strength, independence, intransigence, or other qualities that he thought would increase his authority, or even because he wanted to intimidate certain faculty by seeming to be a "wild man." But that explanation is not available to Summers, because of the apology. And the apology was probably another error, whether or not he should have raised the issue of women's relative scientific aptitudes or tastes in the first place. The apology signaled weakness, and it cannot help a leader to appear weak. Summers has enemies in the Harvard faculty who will be encouraged by his apology to press him for concessions on issues important to them'such as diversity hiring.

The apology was also condescending. It assumed that women's career commitments are so fragile that Summers's remarks at the conference would actually reduce the number of women who choose a science career. Science is a tough career, both highly competitive and not very well paid. It is not for the fainthearted of either sex. If (as I doubt) women are as easily discouraged as Summers's critics believe, their future in science is not bright.

The apology was particularly unfortunate because it dignified the criticisms of Summers's remarks at the conference, and those criticisms were obtuse'which brings me at last to the substantive issue. The critics misunderstood Summers to have been claiming that female scientists are inferior to male scientists. Not at all. He made no comparison between male and female scientists. He was venturing possible explanations other than discrimination (the politically correct explanation) for why there are fewer female scientists than male. The ratio of female to male scientists is unrelated to the average quality of female and male scientists, and indeed is consistent with the average female scientist's being abler than her male counterpart. In fact if, as Summers's critics allege, and Summers admitted was a possibility, discrimination against women is a major cause of the imbalance in the number of male and female scientists, the implication is that the average female scientist is probably abler than the average male scientist. Employment discrimination usually manifests itself in a refusal to hire a person in the disfavored class unless he or she is so superior that the refusal would impose serious costs on the institution and perhaps invite a lawsuit. When anti-Semitism was rife in universities, it was assumed that a Jew had to be abler than a gentile to obtain a university appointment; it would follow that the average Jewish professor was abler than the average gentile professor in that era.

Summers's suggestion that women on average (an essential qualification, obviously) are not as willing to invest as much time in a career as men should not have been controversial. Women who want to have children, as most do, must expect to devote more time to child care that men do. That is a brute fact and has nothing to do with scientific careers as such. Summers's controversial conjecture was that since science-related aptitude tests exhibit less variance in female than in male scores, there are likely to be fewer women in both tails of the distribution'fewer scientific dopes but also fewer scientific geniuses. Imagine two bell curves, each with the same mean but different variance, superimposed on each other. The bell curve with the smaller variance (female) will be narrower and thus have shorter tails. So as one moves toward the end of each tail, the population with the greater variance (male) will increasingly be overrepresented. This will affect the relative number of the two populations in the tails; it may or may not affect the average quality of the members of each population who are in the tails.

Summers rightly offered the variance story as a speculation rather than as an established truth, though another fact consistent with it, besides the test scores, is that at the undergraduate level women's science performance is equal to men's'for at that level, one is not as far out in the tail as at the graduate level. You don't need as much science talent to obtain a B.S. as to obtain a Ph.D.

Could the difference in variance have a biological basis? That is a legitimate subject of inquiry, which is all that Summers suggested. I cited Saletan's article, which unlike most media coverage of the controversy engaged with the issues rather than merely playing it as a fight between angry feminists and an embattled public figure. But Saletan made one silly argument. It is that the likelihood of a biological explanation for the gender imbalance in science is enhanced by the fact that a man has more genes in common with a male chimpanzee than with a female human being. It is a surprising fact, but it may well be entirely explicable by the different biological roles of male and female in reproduction; it need have no connection to scientific aptitude.

Summers said that discrimination may also contribute to the imbalance between male and female scientists. It is certainly in the national interest to eliminate such discrimination, as he strongly believes. Nevertheless the fact that there may be nondiscriminatory reasons for disparities in occupational choice deserves investigation. Discrimination has declined, yet occupational disparities between various groups persist, suggesting that we should be looking for causes that are unrelated to discrimination as well as those that are related. A glance at the composition of different occupations shows that in many of them, particular racial, ethnic, and religious groups, along with one or the other sex and even groups defined by sexual orientation (i.e., heterosexual versus homosexual), are disproportionately present or absent. For example, a much higher percentage of biologists than of physicists are women, and at least one branch of biology, primatology, appears to be dominated by female scientists. It seems unlikely that all sex-related differences in occupational choice are due to discrimination; and therefore someone who explores alternative explanations should not be excoriated. Unless perhaps he is a university president!