STUDY: Eyes Can Reveal Sexual Orientation

A new study claims that the sexual orientation of individuals can be measured from involuntary eye movements in response to arousal due to visual sexual stimuli. Gerulf Rieger and Ritch C. Savin-Williams report how they obtained these results in "The Eyes Have It: Sex and Sexual Orientation Differences in Pupil Dilation Patterns" (PLoS ONE, 2012; 7 (8)).

Live Science reports:

They recruited 165 men and 160 women, including gay, straight and bisexual participants. These volunteers watched separate one-minute videos of a man masturbating, a woman masturbating and neutral landscape scenes. The videos were all matched for brightness so that differences in light wouldn't skew the results.

A gaze-tracking camera recorded the pupils during these videos, measuring tiny changes in pupil size. People also reported their own feelings of arousal to each video.

The results showed that pupil dilation matches the pattern seen in genital arousal studies. In men, this pattern is generally straightforward: Straight men respond to sexual images of women, and gay men respond to sexual images of men. Bisexual men respond to both men and women.

In women, things are more complex, Savin-Williams said. Gay women show more pupil dilation to images of other women, similar to the pattern seen in straight men. But straight women dilate basically equally in response to erotic images of both sexes, despite reporting feelings of arousal for men and not women. 

This is an important advance in measuring sexual orientation and happily is not as invasive as the previous studies which did something similar but used genital monitoring devices.