The Self-Recognition Club Expands: Magpies
Research shows that magpies can display mirror self-recognition behavior. Mirror self-recognition is one of the few tests of behavior that is generally considered to be indicative of the presence of a critical component of consciousness, the ability to recognize oneself. Several of the magpies tested used the mirror to attempt to remove added dots of color on their feathers.
I don’t know all the member species of this club, or all the species that have failed mirror self-recognition. (It should be noted that not every individual of a species must show the behavior, so some negative tests with small numbers of test subjects may not be absolute indicators of capability.) Here are some in each category as I recall offhand, so corrections and additions are welcome:
Mirror self-recognizers (updates marked with *):
Humans (older than about 18 months)
Chimps
Bottlenose dolphins
Magpies
*Asian elephants
*Bonobos
*Orangutans
*Gorillas
*Killer whales
Negative tests of mirror self-recognition:
Cuttlefish
*Capuchin monkeys
So far, all the self-recognizers I know of happen to be vertebrates. It is interesting that not all of them are mammals, though, so any theory explaining these cognitive capabilities needs to be expansive enough to account for the different neural architecture of the avian brain.
Cuttlefish have unusual difficulties with self-recognition in mirrors, I would think: cuttlefish skin texture and colouration is so infinitely malleable, visual recognition would have to be an order of magnitude harder.
Unlike air-breathing creatures, too, who might see themselves in reflecting pools from time to time, where would a cuttlefish ever see itself?
If I recall my Frans de Waal readings correctly, I believe the positive list also includes orangutans, elephants, and gorillas (the last being a long time hold-out). I wouldn’t be surprised a little digging would show that some or all of these are still controversial, though.
One can make an opposite argument about cuttlefish, that being so easily able to control self-appearance would make it particularly easy to test whether one is meeting oneself.
The second one, the lack of mirror-like surfaces encountered naturally, applies equally well to bottlenose dolphins, who passed.
But it does point out that as tantalizing as results from mirror self-recognition studies are, they are not completely applicable across the range of species.
A good read about cognitive ethology in general is provided by Marc Bekoff and Colin Allen.
I recall the elephant “passed” as well.