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Adult great apes show enhanced memory for social events

Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have examined how social models influence memory in great apes. They presented young and adult apes with videos of either a human hand (a social model) or a mechanical claw (a non-social model) building a tower. The results showed that while adult apes remembered towers built by a human hand better than those built by a claw, younger apes did not.

To understand the underlying mechanisms, the researchers used AI-based video analysis, developed in collaboration with colleagues from the University of South Australia, to track participants' heart rates from regular video footage. This technology revealed that the enhanced memory for social events was due to increased attention during social demonstrations.

This study is the first to explore social memory development in non-human great apes. It is in the journal Animal Behaviour.

Primates, including both monkeys and great apes, live in complex social environments where paying attention to others is crucial for interaction and learning. From an early age, they instinctively focus on social stimuli, such as faces and gestures, and tend to prioritize social interactions over non-social objects.

Research has shown that primates, including apes, are more likely to remember an object if it is associated with a human hand rather than a mechanical claw. Even when the observation time is the same, only the social model leads to improved memory. This study expands on these findings by exploring the cognitive mechanisms behind this social memory effect and its early development in non-human great apes.

The study was conducted at the Wolfgang Köhler Primate Research Center in Leipzig, Germany, with 42 great apes—chimpanzees, bonobos, gorillas, and orangutans—ranging in age from 3 months to 47 years.

"We found that apes better remembered a tower when they saw a hand building it rather than a mechanical claw," explains first author Marie Padberg of the Max Planck Institute for Evolutionary Anthropology. "This is because they paid more attention to the actions of a social being rather than a machine."

Interestingly, unlike humans, only adult apes showed this memory improvement. Juvenile and infant apes did not demonstrate enhanced memory when observing the social model. This suggests that while superior memory for social events is a trait shared among primates, only humans exhibit this effect from infancy.

"Non-human ape infants and juveniles did not show superior memory for social events," says senior author Daniel Haun, director of the Department of Comparative Cultural Psychology at the Max Planck Institute for Evolutionary Anthropology. "There could be several reasons for this, including the nature of the objects, the complexity of the task, or the duration of the videos. Further research is needed to determine whether superior social memory at younger ages is truly a uniquely human phenomenon."