Bailey and his colleagues set up a series of experiments in his lab at Northwestern University. In one study, researcher Gerulf Rieger videotaped gay and straight people sitting in a chair, talking. He then reduced them visually to silent black and white outlined figures and asked volunteers to see if they could tell gay from straight. The idea was to find out if certain stereotypes were real and observable.
Based on physical movement and gestures of the figures, more often than not, the volunteers in the study could tell a difference.
"So, is the conclusion that gay people do in fact move differently?" Stahl asked Rieger.
"Yeah, absolutely," he replied.
It's not true 100 percent of the time; it is true on average. The researchers also studied the way gay and straight people talk, and they found differences on average there too.
This research is controversial. Some say it is reinforcing stereotypes. But to Bailey, the stereotypes suggest there's a feminizing of the brain in gay men, and masculinizing in lesbians. Ironically though, when it comes to their sex lives, he says gay and straight men actually have a lot in common.
"Straight men tend to be shallow in terms of focusing on looks. Gay men are shallow, too. Straight men are more interested than straight women in having casual, uncommitted sex. Gay men are like that, too," says Bailey.
"One has the impression that gay men are much more inclined toward casual sex than straight men," Stahl said.
"They're just more successful at it, because the people they're trying to have sex with are also interested in it," Bailey explained.
"But don't you find this interesting that the one big area where gay men are more like straight men is in sex? I mean, that is…both amusing and odd," Stahl said.
"It suggests that whatever causes a man to be gay doesn't make him feminine in every respect. There must be different parts of the brain that can be feminized independently from each other," Bailey replied.
But how and when does this feminizing occur? If the differences were already apparent in childhood, that would point to an early, perhaps even genetic origin — and that's what Bailey and Rieger are testing in a new study using childhood home movies.
In the study, volunteers were asked to rate each child's femininity or masculinity. Stahl took the test and rated two girls highly feminine.
When shown video of a toddler girl running a truck off of a table, Stahl observed, "She's really not girly. Isn't that interesting? She's not girly."
She also observed differences in two boys, one of whom would grow up to be straight, while the other is now gay.