“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.

Psychologists believe that the capacity for mirror self-recognition co-evolved with the complex social capacity that dolphins, apes and elephants have for empathy. Only these species demonstrate “targeted helping,” in which animals respond to the specific needs of injured or elderly family members. “To have higher social behavior” akin to this, Plotnik explains, “you need to have a higher level of self-awareness.”

A human might find it disturbing to find a big spot painted on his or her forehead. Happy quickly lost interest in it, although she continued to play in front of the mirror. As Plotnik and his co-workers report, elephants bathe by throwing mud over themselves. For pachyderms, “attention to detail is not a priority.”