Researchers tested whether chimpanzees can revise initial choices after receiving new information. In five experiments with groups of 15–23 chimpanzees at Ngamba Island Sanctuary, animals received strong (seeing food) or weak (hearing a rattle) cues and could change their initial selection. The chimps behaved rationally two to three times more often than not, weighing both the type and quantity of evidence rather than assigning fixed values to cues.
Chimpanzees Can Change Their Minds — What That Teaches Us About Human Bias
Researchers tested whether chimpanzees can revise initial choices after receiving new information. In five experiments with groups of 15–23 chimpanzees at Ngamba Island Sanctuary, animals received strong (seeing food) or weak (hearing a rattle) cues and could change their initial selection. The chimps behaved rationally two to three times more often than not, weighing both the type and quantity of evidence rather than assigning fixed values to cues.
01:32, 05.11.2025Science
Chimpanzees Can Change Their Minds — What That Teaches Us About Human Bias
Humans like to think of ourselves as consistently rational, but in practice we often cling to comforting beliefs and reinterpret new facts to fit them. A new study published in Comparative Cognition suggests that the ability to revise beliefs in light of new evidence is not uniquely human: chimpanzees can reassess information and change their choices when presented with better evidence.
What the researchers did
Scientists from the United States, Europe and Uganda tested groups of 15–23 chimpanzees at Ngamba Island Chimpanzee Sanctuary. Across five experiments, the researchers showed chimps pieces of food and hid them inside identical containers. The animals received sequential cues about the containers: some cues were strong (for example, actually seeing the food) and others were weak (for example, hearing a rattle). After making an initial choice, each chimp received additional evidence—sometimes stronger, sometimes weaker; sometimes redundant, sometimes novel—and was allowed to either revise the choice or stick with it.
Key findings
The chimpanzees revised their choices in a manner consistent with rational evidence evaluation. Across the experiments, they made choices classified as rational two to three times more often than they made non-rational choices. The animals did not treat each cue type as having a fixed, unchanging value; instead, they weighed the relative strength and the quantity of evidence and learned over time to discount misleading information.
“Chimpanzees did not attribute a fixed value to each type of evidence; instead, they weighed the relative strength of evidence,” the authors write.
Why it matters
These results indicate that meta-cognitive evidence evaluation—thinking about what you know and how strongly you know it—can occur in nonverbal animals. The finding resonates with questions raised by Charles Darwin about apes' intellectual capacities and challenges a strict view of human uniqueness in reasoning. At the same time, the study offers a gentle reminder that humans often fail to update beliefs even when better evidence appears—something our chimpanzee cousins appear better at in these tasks.
Note: This work was originally featured on Nautilus and was carried out under controlled experimental conditions at Ngamba Island Sanctuary.