Your eyes don’t just tell someone you’re lying. They now can tell others your sexual orientation. A new study by Ritch Savin-Williams, a researcher who works at Cornell University as a developmental psychologist, shows that your eyes could give away your sexual orientation through pupil dilation. Pupil dilation is a tell-tale sign of sexual orientation due to the body prepping itself through the autonomic nervous system – which explains the increase in pulse and heavier breathing also.

The concept that pupils could indicate arousal is nothing new to science. In fact, 16th- century Italian women would take eye drops made from belladonna, a toxic herb, which kept their pupils dilated to appear more seductive. This has been studied as late as the 1960s with Eckhardt Hess’ studies on men’s attraction to women of various pupil sizes. It has been found that our pupils dilate over many different stimuli including art, a loved one’s face, hallucinogenic drugs, and obviously sexual stimuli.

The study included 165 men and 160 women mixed between straight, gay/lesbian, and bisexual. One-minute videos were given to the participants to watch of a man masturbating, a woman masturbating, and neutral landscapes. Cameras tracked the dilation of the pupils to indicate the sexual orientation of the person viewing the video.

The study went as expected: Straight men responded to women, bisexual men responded to both men and women, and gay men responded to men. However, with women it was not as straight-forward. Lesbian women responded to women much like a straight man would, but straight women responded equally to both men and women. Now, the common myth that all women are bisexual is not necessarily proven true with the study. In fact, results have produced a theory that women may in fact respond to all sexual stimuli due to a higher risk of rape and sexual crimes throughout history and this actually helps prevent shock to the body, infection, and effectively help the woman still pass on her genetics.

This research has benefits into sexuality studies cross-culturally since pupil dilation is common to everyone regardless of race, nationality, or sexual orientation. This would also benefit psychologists or counselors helping those who are confused on their orientation. This is also less invasive than genital studies which measures blood flow into the genitals of both men
and women. “Some people just don’t want to be involved in research that involves their genitals, “Savin-Williams explained. Genital studies are also hampered by people who suppress their desires which pupil dilation circumvents since it is an completely involuntary action of the body.

The detailed findings can be found in the August 3, 2010 journal of PLoS ONE.