For many people, the festive season is an opportunity to catch up with old acquaintances, sometimes going back years or even decades without face-to-face contact. And now a study published in the journal PNAS shows that we’re not the only species that can recall and recognize friends we haven’t seen for years; great apes are also capable of this.
An international research team, led by Dr. Laura Lewis, came to this conclusion after conducting an experiment with 12 bonobos and 15 chimpanzees living in zoos in the UK, Japan and Belgium. The academics tested the social memory of each of these animals by scrolling photos of two great apes across a screen. One picture showed a primate with whom the bonobos and chimpanzees had lived for at least a year, while the other showed an ape they had never seen before.
As it turned out, the primates spent more time gazing at pictures of their former companions than at those of strangers. Their gaze lingered, on average, on the photos of their old acquaintances for a quarter of a second longer than on the others.
The bonobos and chimpanzees looked for an even longer period of time when they were shown the portrait of a primate with whom they’d had a positive relationship. “It suggests that this is more than just familiarity, that they’re keeping track of aspects of the quality of these social relationships,” noted Christopher Krupenye, one of the co-authors of the study, in a press release.
The findings of this study suggest that bonobos and chimpanzees, which, like Homo sapiens, belong to the hominid family, have far more developed memory capacities than had long been imagined. Never before has the resurgence of a personal memory several years old, or even decades in some cases, been demonstrated in primates. Louise, a female bonobo, was able to recognize her sister, Loretta, and nephew, Erin, from whom she was separated over 26 years ago.
For Dr. Laura Lewis, this indicates that the great apes have even more in common with us than we think. “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,” she emphasized in the release.
There are a host of implications of this discovery, although more work needs to be done in the future to understand whether, like us, primates experience the feeling of missing a loved one they haven’t seen for a long time.
