Chimpanzees may not forget a familiar face—or a behind, a new study says.
In a recent experiment, captive primates were able to identify photos of their acquaintances' rears and match them with the right faces.
The ability suggests that the animals possess mental "whole body" representations of other chimps they know.
Each participating chimp was flashed a picture of another's bum, with visible genitals, then shown the face of the derriere's owner and another face of the same gender.
Both males and females were successful in this anatomical match game, pairing faces and posteriors with much greater frequency than chance alone—but only if the photos showed chimps they already knew.
"Many animals look at parts of the body, the voice, the hands, as separate entities and don't wholly integrate them," said study co-author Frans de Waal of the Yerkes National Primate Research Center at Atlanta's Emory University.
"This study shows that they have whole body integration [because], at least if they know the individuals, they can match the faces and the behinds."
The study appeared recently in the journal Advanced Science Letters.
Nudist Advantage?
Had the chimps also matched strangers, the primates could have been merely picking up on genetic or physical clues to link faces and rear ends, de Waal explained.
"This means that their matching is based on their experience with the individual, not some kind of guesswork that they may do," he added.
No convincing evidence exists that other primates, including humans, could duplicate the feat.
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