NEW PhDs in maths and physics are earned mostly by men, while—in America at least—half of those in molecular biology and neuroscience are awarded to women. In the social sciences and humanities, art history and psychology are dominated by women, and economics and philosophy by men. A new paper thinks prejudice is to blame. The paper’s authors, led by Sarah-Jane Leslie of Princeton university and Andrei Cimpian of the University of Illinois at Urbana-Champaign, hypothesise that the crucial variable is something they call field-specific ability (basically, innate talent)—or, rather, a belief in this quality by those already entrenched in a discipline. They have found that the more existing professors think some special talent, beyond intelligence and hard work, is required to do their subject well, the lower will be the percentage of PhD students in that subject who are women.

Dr Leslie and Dr Cimpian established this by sending questionnaires to more than 1,800 academics working in 30 fields, from astronomy to sociology, at American universities. They asked questions intended to test a number of hypotheses explaining the gender differences between disciplines, converted the responses into numbers, and then plotted those numbers against the fraction of female PhD students enrolled in the disciplines concerned, looking for correlations. Only in the case of academics’ assessments of the need for innate talent was there a correlation—and, as the first two charts show, it was strong. The results on race, illustrated in the third and fourth charts, are also intriguing. Black PhD students show the same types of correlation as women. Americans of Asian descent do not. These differences may reflect the prejudices of recruiters themselves. But it may also be that women and black people themselves, through exposure to a culture that constantly tells them (which research suggests it does) that they do not have an aptitude for things like maths and physics, have come to believe this is true. If that is the case (and Dr Leslie and Dr Cimpian suspect it is), it suggests that a cultural shift in schools and universities, playing down talent and emphasising hard work, might serve to broaden the intake of currently male-dominated and black-deficient fields, to the benefit of all.