Is Gaydar Real? Absolutely.

I.e., this experiment is already selecting for individuals who a) have a high degree of control over their appearance to the author; b) exist within a system—Facebook—which rewards personal disclosure of one’s sexual orientation in vastly different ways. Identifying as gay on a public forum like Facebook—in a manner so that this information is even available to strangers—requires far more deliberation, and often presents far more social costs, than identifying as straight. These disclosures do not bear the same weight—even in a major city.

What the author should have—and could have—done is gather photographic data without selecting for subjects who self-disclose their sexuality.

Right now, the one evident conclusion this paper supports is that certain the certain details of the way one represents himself on Facebook correlate with a propensity for self-disclosure of sexual orientation on Facebook. (Which, remember, doesn’t require that self-disclosure—or a profile photo, for that matter.)

However: if we accept (as this author does) that sexuality correlates with facial geometry in a certain way, then it is quite possible that the facial photographs employed by the experiment are taken from individuals who are very aware of their appearance, and choose to self-disclose their sexuality based on it.

In fewer words, this study seems to suggest that humans can determine if an individual is gay or straight, based on facial features alone, when said individual elects to disclose his sexuality, and maintains personal control over his outward appearance, regardless of that appearance’s fidelity to reality.*

*What I mean here is that people have extraordinary control over which photos represent them on Facebook. The author, I’m guessing, has no way of knowing if any of these photos were manipulated in any way.

It would be interesting to see is there's any difference recognizing gay men and women by straight men and women.

This is the only thing that made any sense in that article:

"We speculate that people overzealously interpret whatever facial factors lead us to classify men as gay. That is, it may be that straight men’s faces that are perceived as even slightly effeminate are incorrectly classified as gay, whereas straight women’s faces that are perceived as slightly masculine may still be seen as straight. That would be consistent with how our society applies gender norms to men: very strictly."