Landmark Study in Science: Chimpanzees Rationally Revise Their Beliefs Based on Evidence
Chimpanzee Trust Research Desk
Science & Conservation Programs
A landmark study published in Science by an international research team, co-authored by Dr. Joshua Rukundo of Chimpanzee Trust, reveals that Ngamba Island chimpanzees flexibly update their beliefs when presented with new evidence.
NGAMBA ISLAND, LAKE VICTORIA — A groundbreaking cognitive study published in the prestigious journal Science has revealed that chimpanzees possess the remarkable ability to rationally revise their beliefs when presented with contradictory evidence — a hallmark of high-level rationality previously believed to be unique to human beings.
The research, titled “Chimpanzees rationally revise their beliefs” (Science, Vol. 390, Issue 6772, p. 521), was conducted by an international team of primatologists and cognitive scientists from Utrecht University, University of California, Berkeley, University of St Andrews, University of Portsmouth, and Ngamba Island Chimpanzee Sanctuary / Chimpanzee Trust, co-authored by Dr. Joshua Rukundo, Executive Director of Chimpanzee Trust.
Key Takeaways from the Study
- Non-Invasive Observational Testing: Between 15 and 23 resident chimpanzees at Ngamba Island Sanctuary voluntarily participated across five distinct experiments.
- Evidence-Driven Decision Making: When chimpanzees were provided an initial clue about which of two boxes contained a food reward and then shown stronger contradictory evidence, they flexibly switched their choice.
- Computational Modeling: Sophisticated computational models proved that chimpanzees were genuinely weighing the quality and quantity of evidence rather than simply relying on associative learning or recency bias.
The Experimental Setup
In the non-invasive tests, chimpanzees were presented with two boxes, one containing a food reward. The experimenters first gave the chimpanzee a weak initial hint indicating where the food might be located. Subsequently, the researchers provided a stronger, more direct clue pointing toward the other box.
Rather than stubbornly sticking to their first choice or blindly following recent sensory stimulation, the chimpanzees evaluated the reliability of both pieces of evidence and updated their choices accordingly. This demonstrated an intuitive, Bayesian-like reasoning process.
“Chimpanzees Are Natural Scientists”
Accompanying the research paper, renowned evolutionary anthropologist Prof. Brian Hare (Duke University) published a featured perspective in Science titled “Chimpanzees are natural scientists” (pp. 444–445). Prof. Hare noted that the cognitive flexibility shown by the Ngamba Island chimpanzees illustrates that the cognitive mechanisms underpinning scientific reasoning — forming hypotheses and updating beliefs when presented with superior data — are deeply rooted in our shared evolutionary history with great apes.
Ngamba Island’s Critical Role in World Science
Ngamba Island Chimpanzee Sanctuary is home to 53 rescued chimpanzees living in a rich 95-acre semi-wild tropical rainforest on Lake Victoria. Because the chimpanzees live in a natural social troop with round-the-clock welfare care, they provide researchers with ethical, non-invasive opportunities to understand great ape intelligence, social dynamics, and evolutionary cognition.
“This publication in Science demonstrates the immense global value of the work we do here at Ngamba Island,” noted Dr. Joshua Rukundo. “Our non-invasive research protocols show that animal welfare and world-class scientific discovery can go hand in hand.”
Academic References & Links
- Original Research: Schleihauf, H., Sanford, E. M., Thompson, B. D., Zhang, S., Rukundo, J., Call, J., Herrmann, E., & Engelmann, J. (2025). Chimpanzees rationally revise their beliefs. Science, 390(6772), p. 521. DOI: 10.1126/science.adq5229
- Perspective Article: Hare, B. (2025). Chimpanzees are natural scientists. Science, 390(6772), pp. 444–445. DOI: 10.1126/science.aeb7565
- News Feature: ScienceDaily (Nov 2025) — Chimpanzees can rationally change their minds when presented with new evidence
To explore more scientific outputs and learn about research partnerships at Ngamba Island, visit our Behavioral Research Program page.