College students in the US find it easier to tell whether a woman is gay or straight from a glance at her face, than they do determining the sexuality of a man from a quick look, researchers have found.
But for both genders, the report said the students' "gaydar" was right more times than it was wrong based on a viewing of just 50 milliseconds - about a third the time of an eyeblink - for each face.
In the study, 129 college students viewed 96 photos of young adult men and women who identified themselves as gay or straight. Photos were only used of people without facial hair, glasses, makeup or piercings to reduce the risk they might provide easy clues. The pictures were cropped so hairstyles could not be seen.
For women's faces, participants were 65 per cent accurate in telling the difference between gay and straight faces when the photos flashed on a computer screen. Even when the faces were flipped upside down, participants were 61 per cent accurate in telling the two apart.
They were 57 per cent accurate in picking the gay men, dropping to 53 per cent when the men's faces appeared upside down.
The difference in accuracy for men's and women's faces was driven by more false alarm errors with men's faces - that is, a higher rate of mistaking straight men's faces as gay.
Lead author Joshua Tabak, a psychology graduate student at the University of Washington, said the different success rates for men's and women's faces may be because participants were more familiar with the concept of gay men than with lesbians, so they may have been more liberal in judging men's faces as gay.
Another possibility was that the difference between gay and straight women was simply more noticeable than the difference between gay and straight men, Tabak said.
A small number of people also had no ability to distinguish gay and straight faces.
Tabak speculated that "people from older generations or different cultures who may not have grown up knowing they were interacting with gay people" may be less accurate in making gay versus straight judgments.
He believed the study's findings conflicted with assertions that if people just kept their sexual orientation to themselves then no one else would know and discrimination would not exist.
The findings are published in the open-access online journal PLoS ONE.
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