A new study finds that apes possess an exceptional social memory, recognizing former groupmates after more than 25 years. This finding underscores the depth and duration of social relationships in our closest animal relatives and suggests a significant cognitive similarity between apes and humans. The study, published today in the journal Proceedings of the National Academy of Sciences, demonstrates the longest-lasting non-human social memories ever documented.
According to senior author Christopher Krupenye, an assistant professor at Johns Hopkins University, the study indicates that chimpanzees and bonobos recognize individuals even after they haven’t seen them for multiple decades. The study also shows a small but significant pattern of greater attention toward individuals with whom they had more positive relationships, suggesting that they’re keeping track of the quality of these social relationships.
The research team worked with chimpanzees and bonobos at various zoos and sanctuaries and invited the apes to participate in the experiment by offering them juice. Using a non-invasive eye-tracking device, the researchers measured where the apes looked to determine if they recognized individuals from photographs they hadn’t seen for a long time. The results indicated that the apes looked significantly longer at former groupmates, regardless of how long they had been apart, and even longer at their former friends with whom they had more positive interactions.
This long-lasting social memory in apes suggests that this kind of memory was likely already present millions of years ago in our common evolutionary ancestors. The work raises the question of whether the apes are missing individuals they’re no longer with, especially their friends and family, indicating that they may have the ability to do so.
The findings deepen people’s understanding of great apes and shed new light on how they could be affected when poaching and deforestation separate them from their groupmates. Disruption to these long-lasting relationships is likely very damaging. In the future, the researchers plan to explore whether these long-lasting social memories are special to great apes or something experienced by other primates, as well as how rich the memories of apes are.