That most authoritative source on all things scientific, the London Daily Mail, reports:
Researchers conducted a series of tests on groups of men and women with similar high IQ ratings. In the first set of tasks, the subjects were given basic puzzles to solve.
Then they were each told how well the others in the group had performed before being given another series of similar tests.
Once they knew the others were good at the tasks, the performance and IQ of both sexes dropped, but women's more significantly.
Scans showed the part of the brain dealing with emotion increased in activity while that associated with problem solving decreased.
The researchers, at the Virginia Tech Carilion Research Institute in the U.S., say the results suggest companies should develop strategies to get the most out of staff who may be 'susceptible to social pressures' in small groups.
This seems plausible to me. Young women studying alone do fine, as school and college grades show, but in groups, women tend to be more cooperative and less competitive than men, more concerned with everybody feeling comfortable, so they tend to turn down their cognitive levels.
This avoids the kind of problems I used to run into when socializing before the Internet gave me a better outlet for the corrosive side of my intellect. At a party, I'd start out popular because I knew enough about most things to be able to ask other guests intelligent questions about their personal field of interest. But I tended to get really interested in what they told me and kept asking questions, which at first they found flattering. But I'd eventually get carried away thinking about the topic and get to the point where I'd ask some extremely unsettling question that the other guest didn't want to think about at all (e.g., So, if the Efficient Markets Hypothesis that you studied at B-School is correct, how do you people in the stocks and mutual funds business add value?).
Very few women allow themselves to get close to committing these kind of faux pas in a social situations, which makes the world a more pleasant place.