A study of 325 men and women, published in the online journal PLoS One, has found a relationship between sexual orientation and the pupil’s dilation in response to erotic stimuli. Researchers report that among men, self-identified gay participants’ pupils reacted more strongly to same-sex images, while straight participants’ pupils had a stronger reaction to opposite-sex pictures. Bisexual mens’ pupils reacted similarly to both.
Straight women, however, “a bisexual arousal pattern”—strong dilation images of both men and women—was common.
In the study, respondents were asked to watch short videos of people of both genders masturbating. An infrared sensor tracked the dilation of each participant’s pupils and recorded which gender caused the greater dilation. The study measured an unconscious physiological reaction rather than genital arousal, “because the measure of pupil dilation is less invasive than previous measures of sexual response, it allows for studying diverse age and cultural populations, usually not included in sexuality research,” the researchers wrote.
“The pupil reacts very quickly, and it is unconscious, so it’s a method that gives us a subconscious indicator of sexuality,” lead study author Gerulf Rieger, of Cornell University, told MyHealthNewsDaily.com.
Among women, lesbians “showed the strongest contrast in pupil dilation to the more versus less arousing sex,” while straight women “dilated more strongly to the less arousing sex than did heterosexual men.” Bisexual women’s reactions fell in between.