http://articles.chicagotribune.com/2010-03-31/entertainment/chi-100331gay-speculation_1_gaydar-gay-men-homosexual-man
J. Michael Bailey, a Northwestern University psychology professor, has published research on gaydar and found that we humans have a staggeringly good ability to judge which way a person swings. "We've found that 'gaydar' has quite a bit, if not perfect, accuracy," Bailey said. "We've done studies where we've brought people into the lab, videotaped them describing the weather in Chicago, and then brought in other people to watch the video and judge them. And they're almost always right." In a 2008 study, Bailey found that gay and straight people who viewed the videos correctly identified straight people 87 percent of the time and correctly identified homosexual people 75 percent of the time.