Perfume's a funny thing. The sense of smell in general is pretty weird, but I think perfume is the best example of how weird. I can picture someone's face (though this does fade if you don't see them), I can hear their voice in my head (especially if I'm reading something they've written; it's almost as if they're reading it to me), but I can't even describe a smell as distinctive as a perfume.
And then, after as little as one date, you can be in a crowd – at a cinema, say – and you find your head turning and your face switching to it's "I'm pleased to see you" expression before you even realize that it's a perfume that's done it. And the back of the woman you're staring at is the back of someone totally unfamiliar, because you don't know her; you just know her perfume.
I remember when I was younger, the first time I had this experience, worrying that there would come a point where I wouldn't be able to walk through a crowd. Too many women who walked by would remind me in an olfactory manner of someone, and I'd find myself snapping my head round to greet the evaporator of the familiar smell, and not have time to replace my expression with one of bemusement or amusement before the next came along.
But it didn't happen. Either I only have the ability to remember one at a time, or the association fades fast enough that I've never had two around at once. (My suspicion is that it's one at a time, at least for me, because you'll notice I talk about perfume in the singular, as if there's a one-to-zero-or-one mapping from women to perfumes, which isn't true. And maybe that's why I have a favorite in one-to-many cases; that there's only one I can remember. I wonder how that's chosen?)
So although I'm often annoyed that I can't remember exactly what people or things look like, and I often wish I could remember exactly what was said, or the exact wording of something I've read (if Google can index 8 billion pages, why can't I index my paltry life?), I'm glad I can't remember perfumes. It would only be a liability.
I also think it's interesting that the perfume-person association's so strong. Like any smell you're exposed to for an extended period, you soon stop noticing a woman's perfume. And yet presumably the sensitivity continues, because the association grows. Or maybe it's just repetition. There's the bell in our noses, there's the saliva in our mouths...
This wasn't what I intended writing about.