In tests, scientists found that the ability – popularly known as a person’s “gaydar” – works on a subconscious level and is more accurate when directed at women.
Volunteers asked to distinguish between photos of heterosexual and homosexual faces were able to do so in just 50 milliseconds – a third of the time it takes to blink. Their accuracy remained greater than chance even when the photos were upside down.
For women’s faces, participants were 65 per cent accurate in guessing sexual orientation when the photos were briefly flashed on a computer screen.
Differentiating between homosexual and heterosexual men proved harder: participants got the answer right only 57 per cent of the time.
The research, published in the online journal Public Library of Science ONE, involved 129 students.
They were each shown 96 photos of young men and women who identified themselves as homosexual or heterosexual. Joshua Tabak, a psychologist at the University of Washington who led the study, said: “It may be similar to how we don’t have to think about whether someone is a man or a woman or black or white. This information confronts us in everyday life.”
Only photos of people without “give away” clues such as facial hair, make–up or piercings were used. The photos were also cropped so that only faces, not hairstyles, were visible. When the faces were flipped upside down, the accuracy of the guesses slipped a little but remained statistically above chance.
The researchers said there were more “false alarm” errors involving photos of men, meaning participants were more likely to make the mistake of thinking a heterosexual man was homosexual.
Mr Tabak said he suspected this may be because people were more familiar with the concept of homosexual men than with lesbians.
Volunteers may therefore have taken a more liberal, pro–homosexual, view of men’s faces.
Not everyone possesses the ability, the research suggested. The tests showed there were “always a small number of people with no ability to distinguish gay and straight faces”, said MrTabak. People from older generations, or cultures where homosexuality is not openly recognised, may have more difficulty making judgments of sexual orientation, he said.