The test gauges self-awareness by determining whether an animal can recognize its own reflection in a mirror as an image of itself.
Animals which have passed the mirror test are Common Chimpanzees, Bonobos, orangutans, dolphins, pigeons and humans. Surprisingly, gorillas have not passed the test, although at least one specific gorilla, Koko, has passed the test; this is probably because gorillas consider eye contact an aggressive gesture and normally try to avoid looking each other in the face.
Human children tend to fail this test until they are at least 1.5 to 2 years old . Dogs and 1 year old children, for example, usually react to a mirror in fear or curiosity, or simply ignore it, while birds often attack their own reflections.
While this test has been extensively conducted on primates, there is also debate as to the value of the test as applied to animals who rely primarily on senses other than vision, such as dogs.
Supposedly, a good way to test the self-awareness of your two-year old.