Men clearly projected more sexy & positive emotions onto the stimuli when the stimuli displayed erect nipples; women did project more positive emotions with erect nipples, but did not differ in their expression of sexy

Burch, R. L., & Widman, D. R. (2020). The point of nipple erection 1: The experience and projection of perceived emotional states while viewing women with and without erect nipples. Evolutionary Behavioral Sciences, Aug 2020. https://doi.org/10.1037/ebs0000244

Abstract: To determine whether female nipple erection is perceived as a sign of sexual arousal or interest, male and female participants were asked to rate photos of real women with and without salient nipple erection on a series of 16 emotional and physiological states, including positive, negative, and sexually aroused states. Nipple erection salience was rated by independent raters, and faces in photos were obscured to prevent discerning emotional states from facial cues. Men clearly projected more sexy and positive emotions onto the stimuli when the stimuli displayed erect nipples. Whereas women did project more positive emotions with erect nipples, they did not differ in their expression of sexy. We also observed that men’s self-ratings of sexy and positive emotions were the same as their ratings of the stimuli. Women, however, reported significantly less sexy and positive emotions for themselves relative to the stimuli.