Economists assume that we can tell what people like by their “revealed preferences”: what they actually spend their time and money on. For example, when people take up tennis or softball and begin playing regularly, we can fairly assume that it is because they have come to enjoy those activities.

As I argued yesterday, this assumption doesn’t work with casual sex for women. There is some amount of “pluralistic ignorance” operating on college campuses: Men and women overestimate each other’s, and even their own sex’s, comfort levels with hook-ups. They participate in hook-ups anyway not purely because they want to but to follow what they believe are widely accepted norms. For example, men, on average, report being comfortable with oral sex and intercourse during hook-ups, but they think most men are more comfortable than they are. More troubling, men think that women are less comfortable with oral sex and intercourse than they are, but they think women are on average more comfortable than not; in fact women report being decidedly uncomfortable in hook-ups that involve oral sex and intercourse.

I see further evidence of this study’s conclusions in the surprise that my male students show during class discussions when they see how unhappy their female classmates are with hook-ups. My female students tell me that the emotional pain that casual sex causes women is not seen by the men who cause it because the women are often ashamed that they care about men who treat them like strangers the next morning. They don’t want the men involved or the rest of campus to know about their tears. This ignorance can be combated by the groups discussed above, and some men’s behavior should change when they know the truth about women’s feelings.