We talked quite a bit about mirror self-recognition in my primate cognition class last semester. From what I understand from the readings and discussions, mirror self-recognition (the ability to recognize that the thing in the mirror is you, and not another member of your own species or something completely different) has only reliably been demonstrated in chimpanzees, orangutans, and humans. For reasons not very well understood, other apes such as gorillas, don't pass the mark test, where a colorless, odorless mark is placed on a location on the subject's body which can only be seen in a reflective surface, and the subject makes self-referential movements in reaction to such a reflection. No other primates, such as monkeys, are known to pass such a test either.
There have been claims of animals such as dolphins and elephants passing the mark test, though we read some of this research, and the evidence seems relatively weak. Which is one reason why it's interesting that a new study has indicated that magpies pass the mark test.
Here's a pic of a magpie with one of the test marks, a yellow pip placed under the beak:
And here's a video of a magpie trying to get the mark off with its claws and by rubbing itself against the bottom of the enclosure, and then checking itself in the mirror to make sure the mark is gone:
One of the necessary controls for an experiment like this is to do a set of experiments with marks that don't change the appearance of the bird. In this research, they used a black mark placed in the same location, which is not visible in the mirror because it blends in with the bird's feather color. They didn't get the same reactions with the black mark as they did with the colored marks. The reason you'd do a control like this is to make sure that the bird is reacting to something like the smell of the mark or how it feels on their body, but purely to the visual information they're getting from the mirror.
From what I've seen, this research looks pretty solid. If so, what does it say about the similarities between great ape and magpie cognition? One idea that was talked about in my primate cognition class about why humans, chimps, and orangs pass the test had to do with conscious knowledge about their body movements, since they all spend a significant amount of their present or recent evolutionary history in the tree canopies, while other large primates don't. The idea is that they have to be much more aware of where their limbs and torso are positioned at all times, or they will fall and suffer terrible injury or death (while other large apes live mostly on the ground, and smaller primates don't suffer as much from such mistakes). I wasn't really buying this argument, but if it's true, how would it gel with the magpie results, assuming they're solid?
I don't know. I'm not sure anybody does at this point. My guess is that mirror self-recognition may be a very specialized cognitive skill that may arise as a by-product of other cognitive skills, but may really say little to nothing about more abstract reasoning or higher cognition. I'd also guess that we'll see a lot more animals pass such tests in the coming years, but time will tell.
Prior et al. Mirror-Induced Behavior in the Magpie (Pica pica): Evidence of Self-Recognition. PLoS Biology, 2008; 6 (8): e202 DOI: 10.1371/journal.pbio.0060202