Chimpanzees are known to interact with dead members of their species, often revisiting corpses, and even showing signs of mourning-like behaviors. But do they show recognition and preference when it comes to skeletons belonging to their conspecifics?
A new study led by Kyoto University has answered affirmatively, by arguing that chimpanzee skulls possess face-like cues, general contours, and eye-nose-teeth arrangements that likely activate a network of brain areas that originally evolved to detect and process faces. In other words, chimpanzees seem to know when a skull is chimpanzee-like due to their brains’ inherent capacity to detect faces (a phenomenon called “pareidolia”).
Previous research has found that African elephants also show more interest in elephant skulls and tusks than in any other stimuli. However, since elephant skulls lose many important facial traits such as their ears or trunks, the recognition mechanisms might be different than in the case of chimpanzees, most probably relying on the elephants’ past experiences.
According to study lead author André Gonçalves, a primatologist at Kyoto University, chimpanzee skulls still retain the general facial arrangements, suggesting that pareidolia may indeed be the mechanism behind chimpanzee’s interactions with their dead conspecifics. Pareidolia “explains why we see illusory faces in things like clouds and rocks, and primate skulls are as face-like as anything in nature,” he explained.
To test this hypothesis, Dr. Gonçalves and his colleagues conducted a series of three experiments using an eye-tracker to map where chimpanzees are looking and for how long. The results revealed that not only do the chimpanzees show the most preference for chimpanzee faces, they also have a strong attentional bias towards chimpanzee skulls, looking the longest and most intently at their teeth.
“When a wild chimpanzee finds a skull, it will likely be attentive to it like no other inanimate object in his surroundings as it bears a resemblance to one of its own,” Dr. Gonçalves said. Further research is needed to fully map the brain mechanisms responsible for this phenomenon, and to investigate whether other species of primates exhibit similar behaviors.
The study is published in the journal Royal Society Open Science.
By Andrei Ionescu, Earth.com Staff Writer