'Gaydar' real and accurate: study

A new study has found people really do have a "gaydar" - and can judge someone's sexual orientation in a blink of an eye.

The research, published in the Public Library of Science journal, found people were able to judge people's sexuality with above-chance accuracy, relying on no more than "grossly impoverished facial photographs", such as grayscale or hair-removed images, presented for only 40-50 milliseconds.

In the study, 129 US university students viewed 96 photos each of young adult men and women who identified themselves as gay or straight.

The images did not include facial hair, make up, and piercings, as these could give clues.

According to the findings, the sexual orientation of women was easier to judge than men's, with participants 65 per cent accurate when differentiating between straight and gay women compared to 57 per cent accurate for men.

People were still able to judge the sexual orientation of the person at an above-chance rate even if the image shown was upside down, although at a slightly lower rate - 61 per cent for women's faces and 53 per cent for men's.

Joshua Tabak, a psychology graduate student at the University of Washington who co-authored the report alongside Cornell University's Vivian Zayas, said the study suggested people make unconscious gay and straight distinctions.

"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," Tabak said.

"This information confronts us in everyday life."

Tabak suspected participants may be more familiar with the concept of gay men than lesbians, so were more liberal in judging men's faces as gay, although he said it may be possible that the difference between gay and straight women is simply more noticeable than the difference between gay and straight men.

Tabak said not everyone has a "gaydar" and in his experiments there are "always a small number of people with no ability to distinguish gay and straight faces".

He said it was unclear why some people have a better gaydar than others, and older generations and different cultures may not have grown up knowing they were interacting with gay people and may therefore be less accurate in judging gay faces.

Tabak said the findings contradict the assertion that if people kept their sexuality to themselves no one would know and discrimination would not exist.