Can the eyes reveal sexual orientation?

Nineteen studies in total were aggregated and analyzed. The results showed that the pupils of heterosexual men dilate much more when viewing stimulating images of women rather than men. The pupils of gay men, on the other hand, dilated more when viewing men compared to women. These results clearly support the hypothesis.

The picture was less clear for women, however. The pupils of heterosexual women did dilate more when viewing heterosexual imagery, but the difference was not statistically significant. Aggregated studies examining lesbian women actually found that their pupils dilated much more when looking at heterosexual imagery, but the authors caution that this result likely can’t be trusted on account of an overall small sample size for lesbian women and because one outlier study completely altered the direction of the link.