While human social memory lasts decades and tracks relationships, less is known about non-human ape long-term memory.<\/p>\n
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.<\/p>\n
Aan eye-tracking task revealed that apes\u2019 attention was biased toward former groupmates over strangers, and this pattern may persist for at least 26 years beyond separation.<\/p>\n
Apes\u2019 memory may also represent the quality of their social relationships: apes looked longer toward individuals with whom they had more positive relationships.<\/p>\n
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.<\/p>\n
\u201cChimpanzees and bonobos recognize individuals even though they haven\u2019t seen them for multiple decades,\u201d said Dr. Christopher Krupenye, a researcher at Johns Hopkins University.<\/p>\n
\u201cAnd then there\u2019s this small but significant pattern of greater attention toward individuals with whom they had more positive relationships.\u201d<\/p>\n
\u201cIt suggests that this is more than just familiarity, that they\u2019re keeping track of aspects of the quality of these social relationships.\u201d<\/p>\n
\u201cWe 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\u2019s so exciting about this study,\u201d said Dr. Laura Lewis, a biological anthropologist and comparative psychologist at the University of California, Berkeley.<\/p>\n
The authors were inspired to pursue the question of how long apes remember their peers because of their own experiences working with apes \u2014 the sense that the animals recognized them when they\u2019d visit, even if they\u2019d been away for a long while.<\/p>\n
They worked with chimpanzees and bonobos at Edinburgh Zoo in Scotland, Planckendael Zoo in Belgium, and Kumamoto Sanctuary in Japan.<\/p>\n
They collected photographs of apes that had either left the zoos or died, individuals that participants hadn\u2019t seen for at least nine months and in some cases for as long as 26 years.<\/p>\n
They also collected information about the relationships each participant had with former groupmates \u2014 if there had been positive or negative interactions between them, etc.<\/p>\n