It exists - and we're all pretty good at it:
Ambady and colleague Nicholas Rule, both at Tufts University in Medford, Massachusetts, wondered about sexual orientation. They showed men and women photos of 90 faces belonging to homosexual men and heterosexual men for intervals ranging from 33 milliseconds to 10 seconds. When given 100 milliseconds or more to view a face, participants correctly identified sexual orientation nearly 70% of the time. Volunteers were less accurate at shorter durations, and their accuracy did not get better at durations beyond 100 milliseconds, the team reports in an upcoming issue of the Journal of Experimental Social Psychology. "What is most interesting is that increased exposure time did not improve the results," says Ambady.
Hat tip: 3QD.