Researchers led by a University of California, Berkeley, comparative psychologist have found that great apes and chimpanzees, our closest living relatives, can recognize groupmates they haven't seen in over two decades — evidence of what’s believed to be the longest-lasting nonhuman memory ever recorded.
The findings also bolster the theory that long-term memory in humans, chimpanzees and bonobos likely comes from our shared common ancestor that lived between 6 million and 9 million years ago.
The team used infrared eye-tracking cameras to record where bonobos and chimps gazed when they were shown side-by-side images of other bonobos or chimps. One picture was of a stranger; the other was of a bonobo or chimp that the participant had lived with for a year or more.
Participants' eyes lingered significantly longer on images of those with whom they had previously lived, the researchers found, suggesting some degree of recognition. In one case, a bonobo named Louise had not seen her sister, Loretta, or nephew, Erin, for over 26 years. But when researchers showed Louise their images, her eyes homed in on the photos.
"These animals have a rich recognition of each other," said Laura Simone Lewis, a UC President's Postdoctoral Fellow in Berkeley's psychology department and lead author of the study, which was published today in the journal Proceedings of the National Academy of Sciences