Chimpanzees can update their decisions based on stronger evidence, much like humans, according to a study published in Science. Researchers at the Ngamba Island Chimpanzee Sanctuary in Uganda found that the animals switched choices when presented with clearer clues about food locations. This flexible reasoning challenges assumptions about animal cognition.
A new study titled 'Chimpanzees rationally revise their beliefs,' published in Science on November 15, 2025 (volume 390, issue 6772, page 521, DOI: 10.1126/science.adq5229), reveals that chimpanzees adjust their choices rationally when faced with better evidence. The research was conducted by an international team including Emily Sanford, a postdoctoral researcher at UC Berkeley's Psychology department; Jan Engelmann, a UC Berkeley Psychology professor; and Hanna Schleihauf, a Psychology professor at Utrecht University. Other contributors include Bill Thompson and Snow Zhang from UC Berkeley, Joshua Rukundo from the Ngamba Island Chimpanzee Sanctuary in Uganda, Josep Call from the University of St Andrews, and Esther Herrmann from the University of Portsmouth.
In experiments at the sanctuary, chimpanzees were presented with two boxes, one containing food. They received an initial hint about the reward's location, followed by a stronger clue pointing to the opposite box. Many animals changed their selection after the clearer information. 'Chimpanzees were able to revise their beliefs when better evidence became available,' said Sanford, a researcher in the UC Berkeley Social Origins Lab. 'This kind of flexible reasoning is something we often associate with 4-year-old children. It was exciting to show that chimps can do this too.'
To distinguish reasoning from instinct, the team employed computational modeling, ruling out explanations like recency bias or simple cue preference. 'We recorded their first choice, then their second, and compared whether they revised their beliefs,' Sanford explained. 'We also used computational models to test how their choices matched up with various reasoning strategies.' The findings suggest rationality—forming and updating beliefs based on evidence—is not uniquely human. 'The difference between humans and chimpanzees isn't a categorical leap. It's more like a continuum,' Sanford noted.
The study has implications for child development and AI design. Sanford's team plans to test belief revision in two- to four-year-olds and expand to other primates. Her prior work on dog empathy and child numeracy underscores animals' cognitive sophistication. 'They may not know what science is, but they're navigating complex environments with intelligent and adaptive strategies,' she said.