And, as per my New Year's resolution…I am "coming out of the closet". No, not that way…
I have prosopagnosia.
More colloquially known as 'face blindness' (but I prefer the scientific term), this odd neurological problem can be acquired or congenital. It's exactly what it sounds like; a difficulty in recognizing faces–the "usual way". (I'll get into the "unusual way" later.) I won't go into much detail (because other people can explain it much better, and I don't know that much detail), but this is a problem with a specific area of the brain–yes, there is a dedicated face-recognition part of your brain–and in prosopagnosia, it doesn't work so well. Like autism, this can be thought of as a spectrum disorder. At the top are the "superrecognizers", who are far better than average at remembering and recognizing faces. At the bottom are the most severe prosopagnosics, who may not be able to recognize themselves in the mirror. I am somewhere in the lower middle, closer to the bottom than the top.
Now, I said that about the "unusual way"…because I can recognize people, just with different methods. I remember voices (an almost foolproof method, unless they're not talking), and I find patterns. For example, my speech therapist wears large, ornate necklaces. This is especially good to know because she sometimes switches between curly and straight hair, and seems to have a near-infinite variety of clothing. One of my friends always has her hair in a ponytail. My brother is usually wearing something red (and even if he isn't, I know what all his clothes look like).
The other method is context. At Japanese class, I expect to see the Japanese teacher, and the other college students. I wouldn't expect to see someone from class at the library, and would most likely be perplexed if they greeted me there. It's when things fall out of context that I have problems…who's in this photo? Who is this random lady talking to me at the grocery store? Is that person at our door a solicitor? Or our neighbor?
(My mother, on the other hand, seems to always be encountering friends in the most unexpected places–at the library, while grocery shopping…I don't understand how she does it. Of course, she doesn't understand how I conclude that a couple boys I know look like Justin Bieber…apparently they don't, "and they don't look like twins, either!" Well, that's what she says; I've been using a combination of their names to address them both, since I can't tell them apart.)
Well, you'd think this is a serious problem (and it is, I believe, far worse for those with acquired prosopagnosia), but I have found one advantage to this "disorder". My mother notices faces, emotion and tone of voice. I notice other things, and quite possibly more things, more patterns, because I have to compensate. Like the blind man who can echolocate*, (though I'm far less impressive than him), one thing doesn't work; other things work better.
*I'm not making this up, Google it!