Study eyes reveal sexual orientation

Pupil reaction as an indicator of sexual orientation

08/06/2012

Based on the eyes can be read the sexual orientation. Like US researchers in the trade magazine „PLoS ONE“ Report is the pupil dilation at the sight of the preferred sex „usually a reliable indicator of sexual orientation.“ The present scientific work provides numerous possibilities for further research.

In their study, the US researchers led by Gerulf Rieger of Cornell University in Ithaca showed that the pupil response differs at the sight of men and women in provocative poses according to the sexual orientation. Thus, in heterosexual people, the pupil expanded when they looked at people of the opposite sex. In the homosexual subjects, the researchers observed the same reaction when looking at same sex and bisexuals showed a widening of the pupils in both men and women. The discovery of the relationship could offer significant benefits in future studies, as sexual orientation has so far been objectively only feasible with the help of measurements of genital arousal. Many subjects find this to be an intimate intervention, so that the determination based on the pupil reaction here offers a clear advantage, the US scientists report.

Pupil response of 325 subjects analyzed
As part of their study, the researchers led by Gerulf Rieger investigated the pupillary response of 325 men and women while they were exposed to various sexual stimuli. When viewing erotic videos of men or women, the subjects showed significant differences in the dilation of the pupils. For some time, there is a suspicion that the involuntary reaction of the eyes subconsciously reflects the sexual orientation, but there is no scientific evidence for this, said the US scientists their study. After interrogating the subjects for their sexual orientation, they showed the 160 women and 165 men erotic video clips and watched the pupil reaction using a special camera that captures the eye movement, line of sight and width of the pupils.

Eye as a mirror of sexual orientation?
It was not only necessary to find out whether the eyes actually made the sexual orientation recognizable, but the researchers also examined further hypotheses, such as whether „the correspondence of pupil dilation to male or female sexual stimuli with self-reported sexual orientation is stronger in men than in women.“ The general assumption that heterosexual men are less responsive to the same gender than heterosexual women has also been scrutinized and refuted in current research. Overall, the pupils of heterosexual men and women widened the most at the sight of the other sex, while homosexual subjects showed a clear pupil dilation at the sight of their own sex in erotic situations. Bisexual subjects responded to both sexes in a similar way. But the researchers also noticed some unusual subtleties.

Even heterosexual men are occasionally interested in their own gender
For example, the reaction of the pupils did not always coincide with the subjects' statements about their sexual orientation. Thus, the pupils of men and women who consider themselves heterosexual would have occasionally widened at the sight of members of their own sex. Men were by no means excluded. Although it has previously been assumed that men tend to have a more strict separation from homosexual and heterosexual preferences than women, surprisingly many men also showed a pupil dilation at the sight of their own sex. This result refutes the prejudice about the sexuality of men, said Rieger and colleagues. „We can clearly prove that there are not only women with flexible sexual desire“, stressed the co-author of the study, Ritch Savin-Williams. According to the US researchers, the usual classification in gay, heterosexual and bi is no longer sufficient to capture the discernible gradations.

Pupil reaction makes the sexual orientation measurable
The evaluation of the obtained data showed that the pupil reaction strongly correlated with the sexual orientation. „If a subject always shows the same involuntary reaction to the images during the 45-minute test period, this indicates that this is a reliable signal“, so the statement of the US scientists. For the first time, they have been able to prove that the pupil reaction can provide measurable information about sexual orientation with the current study of a larger number of people, write Rieger and colleagues in the journal „PLoS ONE“. For the research, the determination of the sexual orientation by means of the pupil reaction offers promising new approaches, since so far the only possibility for the measurement of the sexual orientation in sensors directly at the genitals existed. This intimate and unpleasant method was out of the question for most people.

Research can benefit from the new findings on the pupil reaction
„We wanted to find a less invasive method“, to make the sexual orientation measurable, Rieger stressed and added: „The pupil reaction is just that.“ Thus, the sexual orientation of people can be explored without subjecting them to the unpleasant measurement of genital excitement. Also the measurement of the pupil reaction offers a possibility for example to analyze the sexual orientation of primitive peoples. In this way a comparison with the sexual orientation in modern societies could be accomplished. Ultimately, such research could help decipher the biological basis of human sexuality, write Rieger and colleagues. (Fp)

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