Looks like the eyes have it. (Sorry for the puns.) New research from Cornell University found that when study subjects watched 30-minute erotic videos featuring either a masturbating man or woman, how big their pupils got matched up with their stated sexual orientation. Cool, huh?
Researchers measured 325 men and women of different sexual orientations with an “infrared gaze tracker” (awesome) to record the degree of dilation as well as pupil size to standardize the results. Subjects’ pupils dilated in response to what they said were attracted to, according to the study, published in the journal PLoS One:
Results suggested that pupil dilation is a significant indicator of sexual orientation. Within heterosexual men and women, findings confirmed hypothesized sex differences in sexual response. Furthermore, results indicated that bisexual men have bisexual dilation patterns, and homosexual women have male-typical dilation patterns.
Another cool thing: The pupillary response in heterosexual women wasn’t quite so cut-and-dried as it was for heterosexual men, as researchers reported that women showed a more equal reaction to the films across the board. That might have something to do with how women’s bodies have evolved to protect them from harm:
This sex difference is consistent with previously reviewed theoretical writings and documented sex differences in genital response. Baumeister argued that the sexes evolved to differ in their sexual responsiveness, and this is an adaptation to the sexual behavior of the other sex. One hypothesis related to Baumeister’s proposal is that sexual response has different biological functions for men and women. For men, an important function is to facilitate erection and penetration; for women, to facilitate lubrication and prevent genital injury in case of penetration. Support for this hypothesis is derived from both cross-species and cross-cultural comparisons. Forced copulation in several species and in most human societies indicate that it may have occurred throughout human evolution. Because forced copulation can lead to genital trauma, the female response to any sexual stimulus may have evolved in part to mitigate this risk.
We also like this little footnote in study about how the researchers picked which videos to show:
“In total, 12 male stimuli and 12 female stimuli were selected from a large pool of videos drawn from sites on the Internet. In a pilot study, heterosexual and homosexual men and women rated these videos on the models’ sexual appeal, and the most appealing stimuli were used in the present study.”
We’re guessing the videos were pretty hot.