I read somewhere a while ago that some people did an experiment where they painted a spot on an elephant and showed it a mirror, and in response the elephant reached around with its trunk to touch, not the mirror, but the place on itself where the spot had been painted. This was taken to show that the elephant (and thus elephants in general) are sentient and self-aware in a way that few other animals are.
The kid has been aware of how mirrors work for many months by now, of course. He will look at us through the reflection, and respond to things he sees that are behind him or off to one side but visible in the mirror. And I’ve suspected for a long time that he knew that his reflection was him, although there was nothing (that I noticed) to really confirm that.
A similar situation where it’s unclear that he entirely understands his own image is with photographs. He recognizes his mother and me in pictures, of course, because we fundamentally look the same. But when we show him pictures of himself at various ages, he’s definitely interested, but it’s not clear whether he gets that that’s himself at stages in his growth, or whether he just thinks we’re showing him lots of pictures of babies.
Just a couple days ago, though, he unmistakably reached the level of an elephant in terms of self-awareness. His hair is prone to standing up in a wild curling thicket, and when put in front of a mirror (to brush his teeth, I think), he took some time to look at himself in the mirror and use his hands to try and brush his hair into some semblance of good order.
It failed, of course. Nothing short of a buzz cut is going to keep his hair tidy for long. It was interesting, though, and it made me happy in that special stupid way that comes from being a parent and watching your kid learn how to be human. 8^)