Even Family Separated 26 Years Ago Recognized... The Amazing Memory of Chimpanzees

Experiment Showing Photos of Separated Family and Friends to Apes

A study has found that great apes such as chimpanzees and bonobos can remember the faces of family members or friends they parted from decades ago, just like humans.

On the 19th, a team led by Professor Laura Lewis of Harvard University and Professor Christopher Krupenye of Johns Hopkins University reported in the scientific journal Proceedings of the National Academy of Sciences (PNAS) that in an experiment showing chimpanzees and bonobos photos of family and friends they had parted from long ago, they confirmed cases of remembering family members separated for up to 26 years.

Humans can remember names and faces for a long time through social interactions with family and friends, and such memories can last more than 40 years. However, there is little research known about long-term memory in non-human great apes.

Chimpanzees Remember Family Members Separated for 26 Years

[Image source=Pixabay]

The research team conducted a long-term memory experiment using photos of family and friends on 26 chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) at Edinburgh Zoo in Scotland, Planckendael Zoo in Belgium, and a sanctuary in Kumamoto, Japan.

The study involved showing chimpanzees and bonobos photos on a monitor side by side of family and friends who had lived together for more than a year in the past and had been separated for 9 months to 26 years, as well as completely unfamiliar chimpanzees.

The researchers assumed that if the apes remembered the family or friends in the photos presented, they would look at those photos longer. They measured where the apes looked longer using eye-tracking devices.

They also collected information on whether the past relationship between the participating ape and the ape in the photo was positive or negative to examine correlations.

As a result, chimpanzees and bonobos looked at photos of family and friends much longer than at photos of unfamiliar chimpanzees, regardless of how long they had been apart, and they looked longer at individuals with whom they had a positive past relationship.

In particular, a female bonobo named "Louise" showed clear memory behavior by recognizing her younger sister Loretta and niece Erin, whom she had not met even once after parting 26 years ago, in eight experiments.

"Great Apes Remember Family and Friends They Haven't Seen for Decades"

Chimpanzee family and friend face recognition experiment scene. [Image courtesy of PNAS/Laura S. Lewis et al.]

The research team suggested that these results indicate that social memory in great apes can last more than 26 years, noting that 26 years corresponds to about half of the average lifespan of great apes, which is 40 to 60 years. They explained that this is comparable to human social memory, which is known to last up to 48 years after separation.

Professor Krupenye, who participated in the study, said, "Chimpanzees and bonobos remembered family and friends they had not seen for decades and showed greater interest in apes with whom they had a positive past relationship. This suggests that they remember not only familiarity but also the qualitative aspects of social relationships."

Professor Lewis said, "Remembering and longing for others has been considered a very powerful cognitive mechanism unique to humans. While this study does not definitively conclude that chimpanzees and bonobos share this trait, it raises the possibility."

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