Recognizing your reflection in the mirror as yourself is something we can all do by about age 2, and it's something sort of special about us as humans.
We are one of only a few species in the animal kingdom that can do this. The club includes dolphins, chimpanzees, orangutans, gorillas, and bonobos.
Being able to recognize your reflection in a mirror as yourself is a marker of self-awareness, part of higher intelligence that not all animals have.
Take this jaguar caught in a video taken by photographer Xavier Hubert-Brierre, for example:
Cats and dogs fail the mirror test. They don't realize their reflection is not another animal.
Even gorillas, which do have the self-awareness to recognize themselves in the mirror, can get confused seeing their reflections for the first time (as there aren't normally large mirrors in the jungle if people aren't doing research). This silverback might think he's meeting a rival he wants to intimidate:
On the other hand, chimps are able to recognize their own reflection - though it can take them a little while to figure it out.
But once they catch on, they sometimes use it to check out parts of their body they don't normally see, like this one does:
Maybe the next time you look in the mirror, it'll be with a little more appreciation - for your brain.
Watch the whole video of animals reacting to their reflections here:
[h/t io9]