"Know thyself" has been the guiding principle of many philosophers. Perhaps the first evolutionary step toward that goal is to realize that a "self" exists, distinct from others. For this, a mirror can be a great help. Humans can recognize their own reflection before the age of two. Chimpanzees and dolphins share the ability. Now elephants are known to be members of the club.

Joshua Plotnik, a graduate student at Emory University, and his colleagues bolted a giant plastic mirror inside the elephant enclosure at the Bronx Zoo and watched three Asian elephants progress from curiously sniffing and feeling around and behind the mirror, to eating in front of it, to inspecting their own mouths, to playing peekaboo. One, named Happy, achieved what scientists consider the gold standard of mirror self-recognition, touching a spot on her body that she could not usually see. The scientists had painted a white spot on her head, which she explored delicately with the tip of her trunk while gazing at her reflection.

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