New research reveals that chimpanzees exhibit a remarkable cognitive ability: they “think about thinking,” allowing them to carefully weigh evidence and adjust their plans accordingly. This ability, known as metacognition, mirrors the decision-making processes humans use to assess information and adapt strategies when things don’t go as planned.
Evidence-Based Belief Revision in Chimpanzees
The study, published recently, found that chimpanzees ( Pan troglodytes ) don’t simply react to evidence; they consciously evaluate it. When presented with a task involving finding a tasty treat hidden in one of two boxes, the chimps meticulously examined different pieces of evidence before making a choice. Crucially, they revised their decisions when faced with new, contradictory information.
“When they revise their beliefs, they actually explicitly represent the evidence they have, and they weigh different types of evidences,” explained Jan Engelmann, a comparative psychologist at the University of California, Berkeley, and co-author of the study.
How the Research Was Conducted
Scientists have long known primates can assess evidence, for example, by tracking crumb trails to find food. However, this research delved deeper, investigating whether chimpanzees could perform a key metacognitive task: changing their beliefs in response to new evidence. Engelmann’s team devised several behavioral tests, all centering around food rewards in two boxes.
Here’s a breakdown of the key experiments:
- Initial Tests (1 & 2): Chimpanzees were trained to select a box expecting a reward, then presented with conflicting evidence about which box held the food. They consistently changed their choices based on the strength of the new evidence. Strong evidence, like seeing food through a window in the box, caused more frequent changes in choice than weaker clues like shaking the box.
- Third Test: Prioritizing Weak Evidence: To understand why chimps revised their beliefs, the team introduced a third box, removing the box with strong evidence. When faced with a binary choice between weak evidence and no evidence, the apes consistently chose the box with the weak indication, demonstrating they considered both options.
- Combining Evidence (Test 4): Researchers presented weak evidence twice, either the same clue (rattling the box) or a new one (dropping food into the box). The chimps were more likely to change their choice when they heard two different pieces of evidence, showing they integrated various clues.
- Responding to Contradictory Evidence (Test 5): The researchers introduced evidence that contradicted the initial clues, such as revealing a pebble inside one box that could have caused the rattling sound. The chimpanzees consistently responded to this contradictory evidence by changing their choice, showcasing their ability to link original and new information.
A “High Bar” of Rationality
Cathal O’Madagain, a cognitive scientist at the University of Mohammad VI Polytechnic in Morocco, emphasized the significance of Test 5. “Study five is showing a kind of rationality that studies one and two are not showing,” he stated. He suggested that the research, coupled with earlier studies of chimpanzee rationality, demonstrates that chimpanzees have surpassed a “high bar,” consistently making choices based on evidence and adapting to changing circumstances.
Broader Implications
O’Madagain believes that understanding the minds of other animals isn’t limited by their inherent shortcomings, but rather by our own ability to devise appropriate testing methods. “The biggest constraint on our understanding of other animals’ intelligence is our ability to come up with appropriate ways to check it,” he noted.
Engelmann and his team now plan to extend their experiments to other non-human primates to see if they can pass this rationality test as well, furthering our understanding of cognitive abilities beyond humans.
This research underscores the remarkable cognitive complexity of chimpanzees and provides valuable insights into the evolution of metacognition, revealing that these animals possess a capacity for sophisticated, evidence-based decision-making
