While human social memory lasts decades and tracks relationships, less is known about non-human ape long-term memory. In a new paper published in the Proceedings of the National Academy of Sciences, scientists present evidence that our closest living relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), recognize the faces of familiar conspecifics even after many years of separation: an eye-tracking task revealed that apes’ attention was biased toward former groupmates over strangers, and this pattern may persist for at least 26 years beyond separation; apes’ memory may also represent the quality of their social relationships: apes looked longer toward individuals with whom they had more positive relationships. The findings bolster the theory that long-term memory in humans, chimpanzees and bonobos likely comes from our shared common ancestor that lived between 6 million and 9 million years ago.
“Chimpanzees and bonobos recognize individuals even though they haven’t seen them for multiple decades,” said Dr. Christopher Krupenye, a researcher at Johns Hopkins University.
“And then there’s this small but significant pattern of greater attention toward individuals with whom they had more positive relationships.”
“It suggests that this is more than just familiarity, that they’re keeping track of aspects of the quality of these social relationships.”
“We tend to think about great apes as quite different from ourselves but we have really seen these animals as possessing cognitive mechanisms that are very similar to our own, including memory. And I think that is what’s so exciting about this study,” said Dr. Laura Lewis, a biological anthropologist and comparative psychologist at the University of California, Berkeley.
The authors were inspired to pursue the question of how long apes remember their peers because of their own experiences working with apes — the sense that the animals recognized them when they’d visit,…
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