The human capacity for rational thought makes us unique among the animal kingdom, according to old Aristotle. However, an ever-growing body of research suggests that rationality may not be as distinctive a human quality as one might have thought.
In a study recently published in the journal ScienceResearchers at the Ngamba Island Chimpanzee Sanctuary in Uganda presented the chimpanzees with two boxes: one with food and one without snacks. They were first given an idea as to which one had food. The team then provided the chimpanzees with sequential cues of varying strength indicating which one contained a snack.
“When the initial evidence was strong, the chimpanzees stuck to their initial choice; when the new evidence clearly outweighed the first, they changed their choices,” explains Hanna Schleihauf, assistant professor of developmental psychology at Utrecht University and co-author of the study. Popular science.
Schleihauf and colleagues also incorporated computer models to confirm that the chimpanzee’s responses corresponded to rational belief revision strategies. In other words, they ensured that the primates practiced authentic reasoning and did not, for example, simply favor the most recently presented evidence. Researchers typically associate this type of reasoning with children around the age of four.
“Most strikingly, the chimpanzees also showed metacognitive sensitivity to evidence,” Schleihauf continued. Metacognition is awareness and understanding of our thought processes.
“Not only did they adjust their choices, but they did so in a way that suggests they followed the evidence for their beliefs: when prior evidence was rejected, they revised their beliefs accordingly,” she explains. “This indicates that belief revision based on weighted evidence – a key feature of rationality long considered uniquely human – is also present in chimpanzees.”
The study also suggests that there is not as stark a difference between human and animal cognition as was once believed. It’s more like a progressive continuum of rational reasoning, Schleihauf explains.
However, this study provides much more than just an interesting discovery about one of our closest primate relatives. According to the team, the results have several practical applications.
For example, “the demonstration of rational belief revision in chimpanzees provides a powerful comparative basis for understanding the evolution of human reasoning,” Schleihauf said. By identifying which aspects of rationality humans share with chimpanzees versus those unique to us, researchers can better recognize which ones “develop early in children, which are culturally dependent, and which rely on uniquely human forms of social learning such as teaching or argumentation.”
She adds that the study is important for conservation and animal welfare because it further justifies the protection of great apes, strengthening ethical standards in research and conservation, and creating more cognitively stimulating habitats in sanctuaries and zoos.
Ultimately, the paper joins a host of recent research suggesting that humans simply aren’t as unique as previously thought.
