“That was a 10 out of 10 as far as bitchiness,” Vaillancourt told me.

What Vaillancourt and Sharma found, according to a study published recently in the journal Aggressive Behavior, was, essentially, that the sexy confederate was not going to be making sorority friends anytime soon. The women were far more likely to be bitchy to the sexy confederate, with the large effect size of 2, and their bitchy reactions were more pronounced when the participants were with friends, rather than strangers.

(Aggressive Behavior)

Vaillancourt had always been interested in bullying and popularity, but to her, this showed that women tend to haze each other simply for looking promiscuous.

The clinical term for the womens’ bitchiness is “indirect aggression"— essentially, aggression we don’t want to get caught for.

“You tend to do it such that you won't be detected,” she explained. “Or you make an excuse for your behavior, like, ‘I was only joking.’ Direct aggression is just what it is: physical or verbal aggression.”

Psychologists Roy Baumeister and Jean Twenge have also theorized that women, not men, are largely the ones who suppress each others’ sexualities, in part through this sort of indirect aggression.

“The evidence favors the view that women have worked to stifle each other’s sexuality because sex is a limited resource that women use to negotiate with men, and scarcity gives women an advantage,” they wrote.

Some might argue that it’s only natural for the women in the lab to treat the provocatively-dressed woman poorly. After all, this was a university setting, and in comes an intruder whose, “boobs were about to pop out,” as one participant put it. How untoward!

So Vaillancourt performed another experiment in which she simply showed study participants one of three images: Two featured the conservatively dressed woman and the sexy woman, dressed as described previously. Another showed the sexy woman with her body and face digitally altered so as to appear heavier.

She then asked a different group of women whether they’d want to be friends with the woman in the photo, to introduce her to their boyfriend (if they had one), or to let her spend time with their boyfriend alone.

The participants tended to answer “no” to all three questions for both the heavy and thin sexy women. They were nearly three times more likely, for example, to introduce the conservatively dressed woman to their boyfriend than the thin sexy woman.

To Vaillancourt, this showed that women, “are threatened by, disapprove of, and punish women who appear and/or act promiscuous,” regardless of their weight.

Vaillancourt’s is a small study, but it is one of the first to demonstrate slut-shaming in an experimental context. But women don’t come off very well in past research on indirect aggression, either.