There is a gender gap in some fields of academia. Some are skewed heavily toward women and some are skewed heavily toward men, though some have too little variation to be meaningful.

But why are there any gaps at all? Various explanations have been offered, from the bizarre - sexism among the liberals who dominate academia - to the more bizarre - the belief among those same academic leaders that women are less analytical than men. The most popular explanation is that women are the only gender that can give birth and after that they work less hours and that penalizes them in faculty and tenure hiring. Family-friendly policy is the only area of academia where people wish it was more like the corporate world.

A group recently surveyed over 1,800 graduate students, post-doctoral researchers and faculty members in 30 academic disciplines and, among other things, asked them what qualities were required for success in their fields. The results led them to offer a new explanation for academia's gender gap at the higher levels: with so many PhDs being produced these days, everyone wants to hold out for someone "brilliant" - and that is a quality respondents assume men are more likely to have.

What is "brilliance"? Whatever the vague definition, people in Science, Technology, Engineering and Math (STEM) fields seem to want it. 

"We're not saying brilliance - or valuing brilliance - is a bad thing," says University of Illinois psychology professor Andrei Cimpian. "And we're not saying women are not brilliant or that being brilliant isn't helpful to one's academic career. Our data don't address that. What they suggest is that conveying to your students a belief that brilliance is required for success may have a differential effect on males and females that are looking to pursue careers in your field."

They tested three other hypotheses that might help explain women's underrepresentation in some fields: one, that women avoid careers that require them to work long hours; two, that women are less able than men to get into highly selective fields; and three, that women are outnumbered by men in fields that require analytical, systematical reasoning. 

"We found that none of these three alternative hypotheses was able to predict women's representation across the academic spectrum," Leslie said. "A strong emphasis on brilliance among practitioners of particular fields was the best predictor of women's underrepresentation in those fields."

It's a valid point. An analysis of job placements found that women are not only not penalized in hiring, they are over-represented in hiring compared to men across all fields, but they apply less. Another paper found that just the plan to have children in the future led women to lose interest in the research fast-track at a rate twice that of men.  So it isn't that women are less able to get into fields, they often choose not to be. And some who choose to be may not be the best qualified but may rationalize that as bias.

"There is no convincing evidence in the literature that men and women differ intellectually in ways that would be relevant to their success across the entire range of fields we surveyed," Cimpian said. "So it is most likely that female underrepresentation is not the result of actual differences in intellectual ability - but rather the result of perceived or presumed differences between women and men."

Citation: Expectations of brilliance underlie gender distributions across academic disciplines
Sarah-Jane Leslie, Andrei Cimpian, Meredith Meyer, Edward Freeland, Science 16 January 2015: 347 (6219), 262-265. DOI:10.1126/science.1261375