Some apes may have a social memory that rivals ours, study says. ‘Remarkable finding’
Humans aren’t so special, it turns out.
That is among the conclusions of a long-term memory study that came out Dec. 18. The study, published in Proceedings of the National Academy of Sciences, found that humans’ closest living relatives — chimpanzees and bonobos — remember faces for decades. Their strength of memory rivals that of humans.
“We like to see ourselves as humans as unique, special creatures with incredible intellectual capacities that are very different than every other animal on earth,” Laura Lewis, a postdoctoral fellow at the University of California, Berkeley and researcher in the study, said in a video released by Johns Hopkins University. “This study is showing us how similar we are to chimpanzees and bonobos.”
In the study, scientists worked with 26 chimpanzees and bonobos living in sanctuaries in Japan and Europe. They showed the apes two photos at a time — one of a familiar face and one of a stranger. Using eye tracking technology, the researchers mapped the length of each ape’s gaze as he or she looked at the photos.
And the results were striking. When shown familiar faces, the ape’s gaze would linger on the photo for 11 to 14% longer than when looking at unfamiliar faces. And many of the photos were of group mates from years — even decades — prior. One bonobo named Louise remembered the faces of her sister and nephew from over 26 years prior.
“It’s the longest memory ever recorded in nonhuman animals,” Lewis said in a post on X, formerly known as Twitter.
According to the study, the longest animal memory previously recorded was in dolphins, who recognize each other’s vocalizations for 20 years. The apes’ memories may even rival those of humans, whose social memories begin to decline after 15 years but can last up to 48 years, the study said.
“It’s a remarkable finding,” Frans de Waal, a primatologist who was not involved with the study, told Science.
According to Science, the apes’ strength of memory is useful for such a social species. They — like humans — rely on family and social structures for survival. It makes sense that they too would have strong memories for the faces of their comrades.
The study was born of the researchers’ curiosity about the foundations of human memory. Christopher Krupenye, assistant professor of psychological and brain sciences at Johns Hopkins University and a researcher in the study, said in the video that these results help to give us a better understanding of our own brains and how they evolved.
“It helps us to understand what’s special about our species and how we came to be,” Krupenye said.
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