In blink of an eye, our 'gaydar' clicks into action 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. 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.