Researchers at the Yerkes National Primate Research Center, Emory University, have discovered capuchin monkeys can recognize familiar individuals in photographs. The study, available in the current online edition of The Proceedings of the National Academy of Sciences, showed capuchins were able to recognize photographs of individuals living in their social group, an ability that helps to distinguish familiar individuals from outsiders. The research confirms the ability of monkeys not only to compare and recognize facial images, but the ability to connect faces with individuals they know or do not know, an ability shared with humans. The study also demonstrates capuchins understand the two-dimensional representational nature of photographs.
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, PhD. "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, continues Pokorny.
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. 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," says Pokorny.
Pokorny trained under world-renowned primatologist Frans de Waal, PhD, 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.
For nearly eight decades, the Yerkes National Primate Research Center, Emory University, has been dedicated to conducting essential basic science and translational research to advance scientific understanding and to improve the health and well-being of humans and nonhuman primates. Today, the center, as one of only eight National-Institutes of Health-funded national primate research centers, provides leadership, training and resources to foster scientific creativity, collaboration and discoveries. Yerkes-based research is grounded in scientific integrity, expert knowledge, respect for colleagues, an open exchange of ideas and compassionate quality animal care.
Within the fields of microbiology, immunology, neuroscience and psychobiology, the center's research programs are seeking ways to: develop vaccines for infectious and noninfectious diseases, such as AIDS and Alzheimer's disease; treat cocaine addiction; interpret brain activity through imaging; increase understanding of progressive illnesses such as Parkinson's and Alzheimer's; unlock the secrets of memory; determine behavioral effects of hormone replacement therapy; address vision disorders; and advance knowledge about the evolutionary links between biology and behavior.
The goal of the Living Links Center at the Yerkes National Primate Research Center is to view great apes as a window to the human past by studying their behavior, cognition, neuroanatomy, genes and reproduction in a noninvasive manor. Another goal is to educate the public about apes and to help guarantee their continued existence in the wild.
Originally published Dec. 2, 2009
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