The lack of women in science and engineering has long been a sore spot in academia. Even though girls are just as good as boys (if not better) in science and math, men greatly outnumber women in academic science jobs. Why?

This is not an easy question to answer, partially because many people who legitimately try to answer it are branded as "sexists." At least one person actually lost his job trying to answer this question. Lawrence Summers, the former president of Harvard, proposed the possibility of a difference in the standard deviation of IQs for men and women. His idea, based on more than just mere speculation, was that geniuses and idiots were both more likely to be men, which would explain why it is men who tend to be professors or criminals. For that suggestion, he was essentially fired.

There are other more conventional hypotheses. The politically correct one is gender bias and discrimination. This hypothesis was supported in a damning 2012 PNAS study, which showed that science professors preferred male applicants over female ones for a job as laboratory manager. Even worse, the men were believed to be more competent and were offered more money, despite the fact that the applications were identical in every aspect, except for gender, of course.

But there is also evidence of less malicious forces at play. Cornell University Professors Wendy Williams and Stephen Ceci have presented evidence that women choose to avoid math-intensive fields. This isn't due to a lack of ability, but because they prefer to be doctors or veterinarians. The same authors also argue in American Scientist that motherhood plays an enormous role:

"Our own findings as well as research by others show that the effect of children on women's academic careers is so remarkable that it eclipses other factors in contributing to women's underrepresentation in academic science."

Now, Professors Williams and Ceci are back with yet another study, this time in PNAS, that will certainly add more gasoline to the fire of public debate.

The authors had 363 faculty members read and rate narratives of prospective job candidates for an assistant professorship. In order to avoid tipping their hand in regard to the purpose of their experiment, they varied details of the candidates' lifestyles, e.g., whether or not they were married or had children. Their results showed that both male and female professors of biology, engineering, psychology and economics preferred women over men who shared the same lifestyle by a margin of roughly two-to-one. Furthermore, the same 2:1 preference existed for all lifestyles. The only exception were male economists, who showed no statistically significant gender preference. (See figure.)

The researchers offer a remarkable conclusion:

"Our research suggests that the mechanism resulting in women's underrepresentation today may lie more on the supply side, in women's decisions not to apply, than on the demand side, in antifemale bias in hiring. The perception that STEM fields continue to be inhospitable male bastions can become self-reinforcing by discouraging female applicants, thus contributing to continued underrepresentation, which in turn may obscure underlying attitudinal changes."

In other words, the authors suggest that telling women that male professors are sexist pigs is both untrue and preventing women from applying for academic jobs.

That, if correct, is good news, because it means that the "glass ceiling" for women in science is based on perception rather than actual discrimination. That should make it easier to shatter.

Source: Wendy M. Williams and Stephen J. Ceci. "National hiring experiments reveal 2:1 faculty preference for women on STEM tenure track." PNAS. Published online before print: 13-Apr-2015. doi: 10.1073/pnas.1418878112

(AP photo)