Is Michele Bachmann's husband gay? Don't trust gaydar to settle the question.

I was outed three years ago. Johann Hari, now a contributor to Slate, declared me a gay writer. I'm not sure how he figured it out. Maybe it was my conspicuous interest in homosexuality. Maybe it was my writing style, a photo, or a TV appearance. Somehow, he knew.

Now Marcus Bachmann, husband of Republican presidential candidate Rep. Michele Bachmann, is setting off gaydar alarms. It started as a subtle joke among bloggers. Then it progressed to parody and overt insinuation. On Tuesday, Dan Savage said the Bachmanns' marriage was frigid because Mr. Bachmann may have "tiptoed down" the road to homosexuality "just a couple of inches … maybe six, maybe seven." As evidence, Savage cited Bachmann's "mincing" in a YouTube clip, plus "the sound of his voice."  He concluded that Bachmann "appears to be a lying closet case." On Wednesday, Jon Stewart said Bachmann, who counsels homosexuals to overcome their urges, seems to be doing this "so he can hoard all the gayness for himself." Stewart said Bachmann "dances and sounds not only gay, but center-square gay."

There's nothing new about calling somebody gay based on a lisp or a girlish gait. We all saw, did, or suffered it in grade school. What's unusual is seeing grown-up gays and liberals do it in 2011 with such open ridicule. But don't worry: The new queer-hunters are progressive. They detect homosexuality based on science, not stereotypes. Savage cites a series of studies, written up two years ago in Scientific American, in which college students correctly distinguished gay from straight men based on facial features. He concludes: "Gaydar is for real."

Is it? Can gaydar identify Marcus Bachmann's orientation? Let's look at those studies.

The five key experiments, conducted by Nicholas Rule, Nalini Ambady, Reginald Adams Jr., and Neil Macrae, are impressive. In the first study, undergraduates were shown pictures of 81 men taken from online personal ads. The pictures were stripped of any giveaway context. The students were asked to guess quickly, based on what "most people" or "society" would say, whether each man was "very gay," "somewhat gay", "somewhat straight," or "very straight." Their performance was rated by a "correlation coefficient" (R) which, when squared, shows the extent to which variance in the students' estimates of the men's orientations can be explained by the men's actual orientations—a rough measure of accuracy. They scored an average R value of 0.31, which implies that accurate gaydar accounted for about 9 percent of the variance. *

In the second study, the research team removed various facial clues from the pictures to see whether their absence made a difference. The students still did well. With each man's hair removed, the students scored an R of 0.19. With his mouth obscured, they scored 0.22. With his eyes obscured, they scored 0.26. This suggests accurate gaydar accounted for 4 percent to 6 percent of the variance in estimates.

Even when the students were shown just one feature for each man—hair, mouth, or eyes—they outperformed random guessing. Given only the man's eyes, they scored 0.11 to 0.12. Given only his mouth, they scored 0.11 to 0.15. Given only his hair, they scored 0.24 to 0.27.

The researchers noted that "judgments based on hair only were significantly more accurate than those based on the eyes only or mouth area only." Why? Possibly because hairstyle "is a deliberate aspect of appearance that is groomed to look a particular way." It's culturally influenced and personally expressive. Reading somebody's hair isn't like reading his palm. It's more like picking up a behavioral signal.

And this is the problem, more generally, with using personal-ad photos in gaydar experiments. When you take or choose a photo of yourself for a personal ad, you're trying to send signals. From hair to eyes to mouth, you're conveying your sexuality, aiming at a particular audience, and trying to fit in. That's great for attracting a partner. But it's lousy for testing gaydar. You're making your orientation too obvious.

The researchers recognized this problem. "It is possible that differences in self-presentation may have led to some systematic differences in the appearance of gay and straight men when posting photos of themselves on personal advertisements," they conceded. So, in their final experiment, they tried to eliminate self-presentation. They used pictures from Facebook. They didn't use pictures chosen by the men whose faces were shown. They used pictures posted by friends of these men—pictures showing several people, to minimize the chance that the picture had been selected to emphasize anything about the man in question. The researchers noted that "these album photos are often candid, 'real life' photos (i.e., absent the target's awareness that the photo is being taken), rather than posed shots."