The first five pictures were of cisgender women; the second five pictures were of transgender women.

(Yes, I’m lazy.)

The cisgender pictures are from r/selfie; the transgender pictures are from r/transpassing, a subreddit where people post pictures of themselves to see whether they pass. Both were from the most upvoted pictures of the last month. The trans girl who hadn’t taken HRT was #8, the second girl with a flower crown; an astonishing 37% of voters thought she was cisgender.

Of the five cisgender girls, two were conclusively identified as cisgender, while three had less than sixty percent of voters identify them as either cis or trans. In two cases, the voters leaned towards cisgender, while in one case, the voters leaned towards transgender. Of the five transgender girls, three were conclusively identified as transgender, one was conclusively identified as cisgender, and the remaining girl was not conclusively identified either way, although voters leaned towards her being transgender.

My initial predictions were wrong; I thought that people would be far more likely to misidentify transgender people as cisgender and vice versa than they actually were. In fact, with two exceptions (one cis and one trans), the lean of the vote was in the correct direction.

However, I found the lack of consensus striking. I defined “lack of consensus” as failing to get at least sixty percent of voters to agree on whether you’re cisgender or transgender; by this relatively narrow definition, four women’s pictures were unidentifiable. Using a broader definition, in which fewer than two-thirds of voters agree, six women’s pictures were unidentifiable as cisgender or transgender. As qualitative evidence, several commenters mentioned that, if they hadn’t known that five of the pictures were of trans women, they would have assumed all or nearly all the pictures were of cisgender women.

My interpretation of this data is that base rates matter. Many people– I would roughly guess about half the population– are not readily identifiable as cisgender or transgender if there’s a 50/50 chance that they’re cis or trans. However, in the real world, 99.7% of people are cisgender; for this reason, pretty much all ambiguous people are read as cisgender all the time.

What matters, of course, is not the actual base rate but the perceived base rate. Sophia Kovaleva commented on the original post:

I recently spent 20 minutes arguing with Russian border control agents that my passport is mine, and the incorrect gender marker in it is not a result of “a technical mistake on the part of the organization that issued the passport”. Never mind bone structure or height or the pitch and resonance of the voice – they couldn’t clock me despite seeing my passport and having me literally saying “I’m trans” (well, technically I was saying “I’m changing my sex” in order for this statement to be accessible to them).

Of course, Russia is a very traditional and transphobic country, so the perceived base rate of trans people is extraordinarily low, perhaps zero. No amount of evidence would cause people to update in favor.

I myself have noticed that context matters. When I lived in a Southern state, I passed as male if I cut my hair, wore a button-down shirt, and didn’t talk very much– except when I went to anime conventions. Since many people crossplay at anime conventions, people didn’t expect that someone in male clothing would be male. Now that I live in San Francisco, I rarely pass: people expect butch women to exist. (Inexplicably, having green hair caused me to be read as male, until I started carrying around a baby a lot of the time, at which point people started reading me as female again. I have attempted to persuade my husband to wear a dress in an attempt to confuse people into gendering me as male, but no dice.)

This suggests an unfortunate tradeoff for transgender people. The feminist, trans-friendly places where being perceived as trans is least dangerous are exactly the places where it is most difficult for us to go stealth.