Some animals, including dolphins, elephants, magpies, and apes, have passed the famous mirror self-recognition test. Their behavior when presented with a mirror (for varying degrees of time) implies that they know they are looking at themselves. They twist to look at previously invisible parts of their body, make faces, and blow bubbles. Many researchers have also applied a test whereby they mark the animal surreptitiously in an area the animal itself can't see, or alternate between invisible and visible paint; the animal's reaction to its reflection can be quite telling!
But according to the Onion, only one species can look into a mirror and see the "lively expression and fresh-faced features" of their former selves. While often the impression lasts only momentarily, humans are also endowed with "the immense levels of self-denial necessary to pretend they’re still the same people they’ve always been." The jury is still out on whether orcas feel the same way.
A new study published Thursday in the journal Animal Cognition revealed that human beings are the only animals capable of recognizing the dim shadow of their former selves in the mirror. “As our research shows, Homo sapiens remains the sole species with the ability to behold its reflection and identify the youthful visage it once presented to the world,” said New York University evolutionary psychologist and study lead author Gary Marcus