CHAUVINISTIC men can be petty and infuriating, but that might be as far as it goes. Women are more unnerved by not knowing a man’s views than by overt sexism – so much so that they perform worse in exams.

Rodolfo Mendoza-Denton at the University of California, Berkeley, asked 170 female undergraduates to take a written test. Before the test they were randomly assigned to one of three empty offices, which they were told belonged to their male examiner. The fictional offices were furnished in one of three ways to allow the students to infer the examiner’s view of women. They …