Capuchins never forget a familiar face

EMORY (US)—Capuchin monkeys are able to recognize familiar faces from photographs, an ability they share with humans.

Researchers at the Yerkes National Primate Research Center at Emory University say capuchins are able to recognize photographs of individuals living in their social group, an ability that helps to distinguish familiar individuals from outsiders. The study appears in the current online edition of the issue of the the Proceedings of the National Academy of Sciences.

For the study, the capuchins viewed photographs of four different faces. One of the four pictures was of a capuchin from their own group, which they needed to tell apart from three strangers.

They also needed to do the reverse, differentiating one stranger from three familiar individuals.

“This required monkeys to look at similar-looking faces and use their personal knowledge of group mates to solve the task,” says lead researcher Jennifer Pokorny.

“They readily performed the task and continued to do well when shown new pictures in color and in grayscale, as well as when presented with individuals they had never before seen in pictures, though with whom they were personally familiar.”

Pokorny says the research confirms the ability of monkeys to not only compare and recognize facial images, but the ability to connect faces with individuals they know or do not know, an ability shared with humans.

She says the study also demonstrates that capuchins understand the two-dimensional representational nature of photographs.

Researchers often use two-dimensional images in experiments, yet there is little conclusive evidence to suggest nonhuman primates, particularly monkeys, truly understand the image represents individuals or items in real life.

“The study not only reveals that capuchin monkeys are able to individually recognize familiar faces, but it also convincingly demonstrates they understand the two-dimensional representational nature of photographs,” Pokorny says.

“The fact these monkeys correctly determined which faces belonged to in-group versus out-group members, corresponding to their personal experiences, validates the conclusion capuchin monkeys view images of faces as humans do—as individuals they do or do not know.”

Pokorny trained under Emory primatologist Frans de Waal, who says the study is the first to show face recognition in monkeys is fundamentally similar to that in humans, indicating that face recognition is an evolutionarily ancient ability. De Waal is director of the Living Links Center at the Yerkes Research Center.

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