Monkeys see themselves in the mirror ... sort of

From Scientific American:

Whether or not an animal can recognize itself in the mirror has long been used by scientists as a means of self-awareness. Apes pass the test, but monkeys have been thought to perceive a stranger in their reflection. The results of a new study suggest that what monkeys see is not so simple: although they don't recognize themselves, they also treat their mirror twins differently than they do real animals