Alpha male chimpanzee at Kibale forest National Park (Photo: © Giles Laurent, gileslaurent.com, License CC BY-SA via Wikimedia Commons, Public domain)
Chimpanzees have long been considered clever creatures, but just how intelligent they are continues to be researched. A new study recently published in Science tested whether chimpanzees are metacognitive thinkers. In order to determine this, the great apes had to complete a series of five experiments of increasing complexity to see if they could learn from their mistakes.
The study, which took place in the Ngamba Island Chimpanzee Sanctuary in Uganda, provided the chimps with sensory evidence, specifically auditory, visual, and tactile cues. For each of the five experiments, the chimpanzees were given the opportunity to choose which of the two possible locations food was hidden in.
Experiments one and two had chimpanzees make two choices based on strong and weak evidence. Strong evidence included direct visual and auditory observations (e.g., shaking a box with wood). Weak evidence included indirect visual (traces of food outside the box), and auditory (shaking a box with peanuts).
The first test showed that when weak evidence was presented first, chimpanzees would choose it. But when strong evidence was presented, they revised their choice. In the second, strong evidence was presented first, and the monkeys chose it and adhered to their choice even after weak evidence was presented. This suggests that after receiving strong and weak evidence, chimpanzees can revise their responses to get more accurate results.
The third experiment added a new box with no evidence against the weak and strong evidence boxes. Then, researchers removed the strong evidence boxes to see if chimpanzees would select weak evidence or no evidence. They chose the weak evidence most often (a mean of around 80% of the time) and received the treat.
Experiment four asked chimpanzees to choose between redundant weak evidence that the chimps had experience with (auditory shaking) or new weak evidence (auditory dropping). They showed that they are able to discern between different types of weak evidence, as they chose the new evidence more often than the redundant one, which they had seen fail before.
The fifth and most complex experiment was also the most revealing. Chimpanzees were presented with strong evidence, then another clue, which was either a defeater or non-defeater condition. This means the new clue either undermined the original evidence or did nothing. They were far more likely to change their choice in the defeater condition across both visual and auditory tasks, showing that they adjust their decisions when their original evidence is weakened.
The results showed that chimpanzees can take in evidence and make rational decisions based on past and present knowledge, and also revise these decisions. This breakthrough shows that chimps are rational thinkers, and metacognition is not a uniquely human trait. With this, scientists may be able to test other primates and determine what common ancestor we have that was capable of rational thinking, and find where we diverged.
A new, five-part study tested chimpanzees on their ability to think rationally based on evidence provided.
In each experiment, the great apes showed that they are able to take in different levels of evidence to make decisions and revise their choices.
Two young chimpanzees are playing together in the Gombe National Park in Tanzania. (Photo: Cethuyghe via Wikimedia Commons, Public domain)
The study concluded that chimps have metacognition just like humans, which is significant for future studies to learn more about them, us, and our evolution.
An alpha male chimp in Kibale National Park (Photo: Vincent Mugaba via Wikimedia Commons, Public domain)
Sources: Chimpanzees rationally revise their beliefs, Chimps Can Revise Their Beliefs When Shown New Evidence, Study Finds
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