Can the Eyes Reveal Sexual Orientation?
Through our eyes, the world is revealed. But can our eyes also reveal ourselves?
In particular, the pupil, the black oval located in the center of the iris that allows light to enter, is governed by the autonomous nervous system, which controls unconscious bodily functions. The pupil's size primarily responds to light, but also to arousal. This quirk led psychologists to wonder whether or not pupil size would correlate with someone's sexual interest. In other words, do a person's pupils dilate more in response to sexual imagery that matches their sexual orientation?
Researchers began tepidly exploring this topic more than fifty years ago, but it has experienced a renaissance of late with the rise in eye-tracking technology, which permits precise measurement of subjects' eyes. Thus, a plethora of studies have been recently published, enough to allow a team of psychologists from the United Kingdom and Canada to pool and analyze the available research to discern if indeed a person's pupils dilate when viewing stimulating images that line up with their gender orientation.
Their meta-analysis was published in September to the Archives of Sexual Behavior.
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.
A prominent hypothesis called the preparation hypothesis could explain the mixed results in women, according to the authors. It suggests "that any strong sexual cues provoke an indiscriminate arousal response to prepare a woman for the possibility of a sexual encounter."
Why explore whether pupil response correlates with sexual arousal? Right now, scientists often measure sexual arousal in experiments by recording genital responses, but this is a highly invasive technique. "Pupillary responses could offer an additional or even alternative physiological measure of sexual arousal and sexual orientation to these measures, due to its non-invasive, instantaneous, and involuntary reaction to sexually appetitive content," the reviewers say.
"However, the mixed findings... also demonstrate a clear need to increase research on women... and for the development of standardized testing protocols and materials."
Source: Attard-Johnson, J., Vasilev, M.R., Ó Ciardha, C. et al. Measurement of Sexual Interests with Pupillary Responses: A Meta-Analysis. Arch Sex Behav (2021). https://doi.org/10.1007/s10508-021-02137-y