Chimpanzees can make rational decisions like humans, study suggests

The researchers examined how chimpanzees responded to new information about the location of a treat and if they were able to update their conclusions when given new clues.

For the study, published in the journal Science, the team presented two boxes containing a piece of food to the chimpanzees and then provided them with evidence about one of the boxes to suggest it contained the reward.

This could involve shaking it to make a sound or directly showing them what was inside.

The chimpanzee was then prompted to make an initial choice of where they thought the food was hidden before the researcher provided a new piece of evidence.

The researchers found that when the first clue was stronger, the chimpanzees tended to stay with their original choice but when the new evidence was stronger, they switched boxes.

The team also pointed out that when they revealed that one of the clues was misleading, such as that a box only contained a picture of food, the chimpanzee understood that the initial evidence was not valid.

Senior author of the study, Dr Esther Herrmann from the University of Portsmouth, said: “Our findings reveal that humans aren’t the only ones who make rational decisions based on evidence – chimpanzees, our closest living relatives, also weigh the strength and quality of the evidence before making decisions.”

Professor Josep Call, from the University of St Andrews and co-author of the study which also involved Utrecht University in the Netherlands and University of California Berkeley, said: “This study opens a new avenue of research into the psychological mechanisms underlying decision-making in chimpanzees.

“Together with previous work on bargaining games, it contributes to portray chimpanzees as rational decision-makers.”