The truth of who attracts you could be in your eyes, regardless of whether you are gay, straight or any other member in the LGBT Community.

A new study has found that pupil dilatation is an accurate indicator of sexual orientation and attraction, but how does it works? It was discovered that when people look at erotic images and become aroused, their pupils dilate in an unconscious reaction.

The study researcher, Savin-Williams, says that this study is the first large-scale experiment to show that pupil dilatation matches what people feels when they are feeling turned on.

Not many people are aware that pupils dilate in response to any exciting or interesting stimulus. This includes seeing a beautiful piece of art or seeing the face of your loved ones. Pupil dilatation is a sign that the nervous system is ramping up.

For the study, Savin-Williams and his colleague Gerulf Rieger, recruited 165 men and 160 women, including gay, straight and bisexual participants. All the volunteers watched in separate videos of a man masturbating, a woman masturbating and neutral scenes. All the videos were edited to have the same brightness so that any light differences wouldn’t affect the results.

A gaze-tracking camera recorded the pupils of the volunteers during watching these videos, and then they measured the size changes of the pupil. Volunteers also had to report their own feelings of arousal to each video.

The results showed that the pattern of pupil dilatation in men is generally straightforward: Gay men respond to sexual images of men, straight men respond to sexual images of women, and bisexual men respond to both men and women images.

However, in women things are more complex. Gay women show more pupil dilatation to images of other women, but straight women dilate basically equally in response to erotic images of both sex genders, despite reporting feelings arousal for men and not for women. Sex researchers aren’t sure why this happens.

“This doesn’t mean that all straight women are bisexual in secret, but that their subjective arousal doesn’t necessarily match their body’s arousal”, says Savin-Williams.

This discovery could be used for conduct cross-cultural studies of sexuality, given that pupil dilatation is universal and does not depend on race, culture or religion. This method could also be used to help people who are feeling confused about their sexual orientation.