A new study by Cornell University researchers has found that sexual orientation can be discerned by observing an individual's pupil dilation.
The Huffington Post reports that the study, led by researcher Ritch Savin-Williams, involved showing erotic videos to gay, straight and bisexual men and women while monitoring and recording the dilation of the test subjects' pupils.
Savin-Williams and his Cornell colleague Gerulf Rieger recruited 165 men and 160 women and showed them separate one-minute long videos of either men or women masturbating and neutral landscape scenes. Brightness was kept constant in order to obtain accurate measurements.
A gaze-tracking camera recorded the test subjects' eyes as they watched the explicit videos. Subjects also reported their feelings of arousal upon viewing the masturbating men and women. The researchers found that the pupils of straight men responded to images of women, while those of gay men dilated upon viewing men pleasuring themselves. Bisexual men responded to images of both men and women. Among the female test subjects, the pupils of gay women dilated the most when viewing the woman masturbating, but straight women responded equally to videos of both sexes.
Savin-Williams' research is significant because it is a far less invasive method of gauging sexual arousal than measuring genital size and blood flow. Savin-Williams said that the new test could even be used to help individuals who may be confused about their sexual identity.