What's good for the goose

Have you ever spotted someone who you might have thought was transgender somewhere like a restaurant and spent any amount of time, either by yourself or in a group, trying to figure out whether that person was really male or female?

I've done it and still catch myself doing it when someone tweaks my gender detector. Well, not so much trying to determine someone's "true" gender, but wondering if they're trans. Having experienced this from the perspective of the person being analyzed, I know it's a really shitty feeling to have anyone deconstruct you like that. So why do I still do it?

Does it really matter to me if someone's trans or not? I mean, even if I'm convinced they are, I'm never going to walk up to them and let them know. I'm not going to treat them any differently...well, maybe I'd be a bit nicer.

I just wonder what it is within us that springs our inner detective into action when a couple of things seem out of place on the gender spectrum. Is it a cultural thing? Does it have something to do with some sort of primal mating urges? Are we just nosy?