In what may put many of us to shame, apes instantly recognize family and friends that they haven’t seen in more than two decades, which is the longest ‘social memory’ in a non-human animal ever documented.
Offering key insights into how human social recognition evolved, the study from Johns Hopkins University came about after researchers noticed how the animals seemed to recognize humans they’d spent time with, even if it had been a long time between visits.
“We have really seen these animals as possessing cognitive mechanisms that are very similar to our own, including memory,” said lead author of the study Laura Lewis, a biological anthropologist at the University of California, Berkeley. “And I think that is what's so exciting about this study."
Working with chimpanzees and bonobos at zoos in Scotland, Belgium, and Japan, the researchers prepared sets of photos that featured one familiar animal (who had either died or been moved to another enclosure) and that the apes had never seen before. Their focus was then measured with a non-invasive eye-tracking device to determine if the animals did actually spend more time looking at ‘friends’ or family. And they did.
The apes spent significantly more time looking at animals that had formerly been part of their social group and they had positive associations with. One ape, a bonobo named Louise, had not seen her sister Loretta and nephew Erin for 26 years, but over eight trials she consistently focused on their images compared to the unfamiliar animal.
These findings have excited the researchers, as given the common ancestor humans share with these animals, social memory appears to have been an important factor in the evolution of our species.