The mirror test is a way to determine how self-aware animals are, how bright they are. Does the animal, on looking in the mirror, see another animal or its own reflection? Is it aware that the image it's seeing is an image of itself? The test is old; Darwin showed a mirror to an Orangutan and it made faces, but he realized it was ambiguous; did the ape make faces at itself or another ape? The mirror test is a little more sophisticated now, in that researches put an odorless spot on the animal somewhere it can't see without a mirror and wait to see if it realizes the spot on the reflection is a spot on its own body.
All of the great apes pass the mirror test: gorillas, both species of chimp, some gibbons, and, of course, humans after the age of 18 months. Elephants, dolphins, orcas, and even some magpies pass it. Pigs are believed to be mostly capable of using mirrors. Cats don't pass the test.
Of course, before you can use a mirror, you have to learn what a mirror is. Humans blind from birth and later given sight initially react to the mirror, even in adulthood, as they would to another human until they learn its their own reflection. So do animals, hence chimps that initially make threat displays and then calm down and use it as an aid to self-grooming.
I have two cats. Sappho, my dark tabby, ignores mirrors while Babygirl, my tubby calico, spends lots and lots of time staring into a mirror. Is one cat smarter or more self-aware than the other? When Sappho ignores the mirror, is it because she recognizes it as herself and dismisses it or because she sees it as a non-responsive other cat that she can't play with? When Babygirl plants herself in front of a mirror and stares for minutes on end is it because she recognizes herself, or because she sees another cat and doesn't understand? Since Babygirl hates other cats (she was abandoned in an apartment complex with many strays and learned to hate cats. Then she was rescued by Mildcats at ASU, whence I adopted her.), it seems odd that she would sit inches away from what she deemed to be another cat.
So which cat is smarter? Which more self-aware? Obviously neither metric belongs on a binary scale. I think Babygirl is interested in and confused by the mirror, because she's aware that the image of me isn't me and that the image of the other cat isn't another cat, but I don't think she recognizes the image as a reflection of herself. I've no idea what she makes of the image of me. I like to think that Sappho is more clever, but I have no idea where she stands vis-a-vis the mirror test. She's never shown any interest in mirrors and I have no data, thus no conclusions, however tentative. Why does Sappho not care where Babygirl really, really does? I think it's because Sappho doesn't have Babygirl's traumatic history (Sappho's also a rescue, but I found her crying in a parking lot after only a few days of abandonment in an area with few strays. She was filthy and starving, but unscarred.), so the mirror doesn't pose the same troubling dilemma for her. I'm probably reading way too much into this, but I think Babygirl really wants that other cat to go the hell away; I know she often wishes Sappho would.
In any event, self-awareness and the like are interesting subjects. I kind of want to start breeding programs to try and make intelligent, tool-using cats. And dolphins. And pigs. But not magpies. Those little fuckers can burn.*
* Not really. Magpies are probably cool. But fuck dingoes. They eat babies.