A new study published in Science by researchers from UC Berkeley and Utrecht University demonstrates that chimpanzees can update their beliefs rationally when presented with new or contradictory information. Through a series of five carefully designed experiments, the authors show that chimpanzees are able to evaluate evidence, compare its strength, and revise their decisions accordingly—a level of reasoning previously thought to be uniquely human.

In elDiario.es, Miquel Llorente (Comparative Minds Research Group) was invited to comment on the study. He highlighted that “this is the first time it has been so clearly demonstrated that chimpanzees revise their beliefs rationally when confronted with conflicting evidence.” Llorente praised the methodological rigor of the work, noting that “five impeccably designed experiments show that chimpanzees distinguish between new and redundant information and are capable of evaluating evidence about evidence—a surprisingly reflective capacity.”

He added that these results reopen a fascinating debate on metacognition—the ability to think about one’s own knowledge—and its evolutionary roots. “Chimpanzees don’t just react to what they see or hear; they seem to evaluate whether their own information is reliable and decide accordingly. This gives us a glimpse into how the foundations of rationality may have emerged in our evolutionary history.”

🔗 Read the full article in elDiario.es (in Spanish):

Un estudio demuestra que los chimpancés pueden razonar y revisar sus creencias al recibir nueva información

📖 Original study reference:

Schleihauf, H., Sanford, E. M., Thompson, B. D., Zhang, S., Rukundo, J., Call, J., Herrmann, E., & Engelmann, J. M. (2025). Chimpanzees rationally revise their beliefs. Science, 390(6772), 521–526. https://doi.org/10.1126/science.adq5229