What is it about?
In this study we show that chimpanzees and bonobos, humans’ closest-living phylogenetic relatives, likely remember groupmates for a decade or longer and that their social relationships may also shape their long-term memory. We used a special non-invasive camera for tracking where apes looked as they viewed images of members of their species. Apes spent much more time looking at pictures of former groupmates than at pictures of strangers, suggesting that they recognized their past social partners, even partners they hadn’t seen for over 26 years! We also demonstrate that chimpanzees and bonobos may remember the quality of their past social relationships: apes looked the longest at individuals with whom they had the most positive relationships, individuals we might call their friends.
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Why is it important?
As humans, we have remarkable memory for others that lasts decades, incorporates important information about social relationships, and is shaped by our emotions. Other animal species like Japanese macaque monkeys, sheep, and elephants also have long-term memory for others that can last years – and dolphins can remember others for up to 20 years. However, up until now only one other animal on the planet – ravens – have been shown to incorporate information about relationship quality into their long-term memory. Nonhuman apes are very social and thus should also benefit from robust knowledge about current, past, and potential future social partners and relationships. Our results represent the longest-lasting social memory found in any nonhuman animal species, and demonstrate that humans’ closest great ape cousins may also incorporate information about social relationships into their long-term social memory. Our research suggests that important properties of human social memory are shared with other apes, and may have provided the foundation for the emergence of complex cooperative relationships that operate across long distances, time-scales, and group boundaries—such as intergroup trade.
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This page is a summary of: Bonobos and chimpanzees remember familiar conspecifics for decades, Proceedings of the National Academy of Sciences, December 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2304903120.
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