It only takes a 50ms glimpse (that's one twentieth of a second) of a man's face for people to recognise his sexual orientation. Nick Rule and Nalini Ambady said such an ability could have evolved for reasons relating to sex or may simply reflect a more general human ability to detect the characteristics of others with impressive efficiency. Past research for example has shown that trustworthiness is judged in less than a tenth of a second and that a company's profits can be discerned from the appearance of its chief executive.
Twenty-two male and sixty-eight female undergrads were presented with photos of 90 men's faces (half were homosexual) for either 33ms, 50ms, 6500ms or 10,000ms. The anonymous photos were taken from an internet dating site where posters stated their sexual orientation. Any photos featuring facial hair, glasses or jewellery were not used.
At 33ms, the presentation was too quick for the students to consciously 'see' the faces and, perhaps unsurprisingly, their ability to determine the men's sexuality was no better than if they were simply guessing. However, at 50ms - just long enough for the faces to be consciously seen - the students' accuracy grew to 57 per cent, which is significantly better than chance performance. Accuracy didn't increase with the longer exposure times, suggesting that all the relevant information for making the judgment had already been extracted by 50ms.
In a second study, the researchers guarded against the possibility that the men in the dating photographs had deliberately accentuated their sexuality. This time photos were taken from the social website Facebook, where they had been posted by people other than the subjects of the photos (so deliberate accentuation of sexuality was less likely). Hairstyles were also removed from the photos. Again, from just a 50ms exposure to men's faces, the 15 undergraduate participants were able to recognise the men's sexual orientation with an accuracy better than chance.
"The finding that male sexual orientation can be accurately perceived in such a short period of time is striking," the researchers said. "Although previous work has shown that 'thin slices' of behaviour are remarkably rich in providing information about people, none have sliced as thin as 50ms."
RULE, N., AMBADY, N. (2008). Brief exposures: Male sexual orientation is accurately perceived at 50ms. Journal of Experimental Social Psychology, 44(4), 1100-1105. DOI: 10.1016/j.jesp.2007.12.001
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.