No matter your sexual orientation, your eyes could be giving you away, according to a new study, published in the journal PLoS ONE. (Photo: Creative Commons: Flickr/orang)

No matter your sexual orientation, your eyes could be giving you away, according to a new study, published in the journal PLoS ONE. Researchers found that pupil dilation is an accurate indicator of sexual attraction, and since it's involuntary, it could be used to determine what gender a person is attracted to.

When people look at erotic images and become around, their pupils involuntarily dilate, which can be used to measure orientation and sexual orientation without invasive genital measurements, researchers said. This is the first study to prove that pupil dilation matches sexual attraction, researchers said.

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"So if a man says he's straight, his eyes are dilating towards women," Ritch Savin-Williams, study author and developmental psychologist at Cornell University, told LiveScience. "And the opposite with gay men, their eyes are dilating to men."

But it's not just sexual attraction -- your pupils dilate to things such as a piece of art or a loved one's face. Dilation is a symptom of your autonomic nervous system ramping up, which includes your pulse and breathing becoming quicker.

Until now, scientists looking to measure arousal did so by measuring blood flow to the genitals via a circumference measurement for men and a probe for women. However, these measurements come with problems, as not only are they invasive, but people can also suppress their arousal.

"Some people just don't want to be involved in research that involves their genitals," Savin-Williams said.

The findings could have a broad range of applications, researchers said. Since pupil dilation is involuntary, the technology could be used to conduct cross-cultural studies on sexuality. In addition, people who are confused about their sexuality could use it to sort through their feelings, Savin-Williams told LiveScience.

Researchers said the next step is to look at pupil dilation while measuring the blood flow to a person's genitals, to see how they correspond.