Columbia Business School has run numbers [to show] men overestimate their abilities by some 30%, [whereas] women routinely underestimate their abilities. We talked to a lot of psychologists who were working in business schools who put men and women in front of scientific reasoning quizzes. The women will routinely think they have done less well than they have done. The men will think they have done better than they have done. In reality, they have done about the same.