So there’s been some media attention recently to this study which found they were able to accurately predict sexual orientation with 91% for men and 83% for women. Sadly, everyone is focusing on the misleading idea that we can somehow use this algorithm to decloak who is gay and who isn’t rather than the really interesting fact that this is suggestive of some kind of hormonal or developmental cause of homosexuality.
Rather, given 5 pictures of a gay man and 5 pictures of a straight man 91% of the time it is able to correctly pick out the straight man. Those of us who remember basic statistics with all those questions about false positive rates should realize that, given the low rate of homosexuality in the population, this algorithm doesn’t actually give very strong evidence of homosexuality at all. Indeed, one would expect that, if turned loose on a social network, the vast majority of individuals judged to be gay would be false positives. However, in combination with learning based on other signals like your friends on social media one could potentially do a much better job. But at the moment there isn’t much of a real danger this tech could be used by anti-gay governments to identity and persecute individuals.
Also, I wish the media would be more careful about their terms. This kind of algorithm doesn’t reveal private information it reveals sensitive information inadvertently exposed publicly.
However, what I found particularly interesting was the claim in the paper that they were able to achieve a similar level of accuracy for photographs taken in a neutral setting. This, along with other aspects of the algorithm, strongly suggest the algorithm isn’t picking up on some kind of gay/straight difference in what kind of poses people find appealing. The researchers also generated a heat map of what parts of the image the algorithm is focusing on and while some of them do suggest grooming based information about hair, eyebrows or beard play some role the strong role that the nose, checks and corners of the mouth play suggests that relatively immutable characteristics are pretty helpful in predicting orientation.
The authors acknowledge that personality has been found to affect facial features in the long run so this is far from conclusive. I’d also add my own qualification that there might be some effect of the selection procedure that plays a role, e.g., if homosexuals are less willing to use a facial closeup on dating sites/facebook if they are ugly the algorithm could be picking up on that. However, it is at least interestingly suggestive evidence for the prenatal hormone theory (or other developmental theory) of homosexuality.