Rosa Rubicondior: Creationism Refuted - Unlike Creationists Chimpanzees Change Their Mind When the Evidence Changes

Ngamba Island Chimpanzees, Uganda

Photo: Sabana Gonzalez, UC Berkeley

New psychology study suggests chimpanzees might be rational thinkers | Letters & Science

A recent study has shown that chimpanzees, unlike creationists, are capable of rationally revising their beliefs when presented with new information – another trait they share with most humans.

Creationists, by contrast, tend to take pride in refusing to change their minds. For them, admitting error would be a sign of weakness: a capitulation to the supposedly corrupting influence of scientific evidence that threatens to lure them away from the ‘truth’. In their circular logic, it must be true because they believe it, and they believe it because it is true - a circular logic designed to make intellectual bankruptcy look like a virtue called 'faith'.

Chimpanzees, unburdened by irrational superstition or egos in need of constant reinforcement, appear far more interested in being right than in demonstrating unwavering devotion to a demonstrably wrong belief system.

Interestingly, the chimpanzees can do something human children do by the age of about 4. The ability to asses evidence and base opinions on it, is, of course, the basis of science - which may be the reason creationists struggle to understand it and reject evidence as the basis of opinion, believing themselves to be capable of simply knowing the truth, like a child below the age of 4. So we have a continuum of increasing intellectual ability and integrity from toddlers and creationists through chimpanzees and 4-year-old humans to human adults. The study, carried out by a large research team that included UC Berkeley Psychology Postdoctoral Researcher Emily Sanford, UC Berkeley Psychology Professor Jan Engelmann, and Utrecht University Psychology Professor Hanna Schleihauf, has just been published in Science and is summarised in a University of California Berkeley news item.

New psychology study suggests chimpanzees might be rational thinkers
Chimpanzees may have more in common with human thinkers than previously thought. A new study published in Science by researchers provides evidence that chimpanzees can rationally revise their beliefs when presented with new information.
The study, titled “Chimpanzees rationally revise their beliefs,” was conducted by a large research team that included UC Berkeley Psychology Postdoctoral Researcher Emily Sanford, UC Berkeley Psychology Professor Jan Engelmann and Utrecht University Psychology Professor Hanna Schleihauf. Their findings showed that chimpanzees — like humans — can change their minds based on the strength of available evidence, a key feature of rational thought.

Working at the Ngamba Island Chimpanzee Sanctuary in Uganda, the researchers presented chimps with two boxes, one containing food. Initially, the animals received a clue suggesting which box held the reward. Later, they were given stronger evidence pointing to the other box. The chimps frequently switched their choices in response to the new clues.

Chimpanzees were able to revise their beliefs when better evidence became available. 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.

Dr. Emily M. Sanford, co-lead author
Department of Psychology
University of California, Berkeley

To ensure the findings reflected genuine reasoning rather than instinct, the team incorporated tightly controlled experiments and computational modeling. These analyses ruled out simpler explanations, such as the chimps favoring the latest signal (recency bias) or reacting to the most obvious cue. The models confirmed that the chimps’ decision-making aligned with rational strategies of belief revision.

We recorded their first choice, then their second, and compared whether they revised their beliefs. We also used computational models to test how their choices matched up with various reasoning strategies.

Dr. Emily M. Sanford.

The study challenges the traditional view that rationality — the ability to form and revise beliefs based on evidence — is exclusive to humans.

The difference between humans and chimpanzees isn’t a categorical leap. It’s more like a continuum

Dr. Emily M. Sanford.

Sanford also sees broader applications for this research. Understanding how primates revise beliefs could reshape how scientists think about learning, child development and even artificial intelligence.
This research can help us think differently about how we approach early education or how we model reasoning in AI systems. We shouldn’t assume children are blank slates when they walk into a classroom.

Dr. Emily M. Sanford.

The next phase of her study brings the same tasks to children. Sanford’s team is currently collecting data from two- to four-year-olds to compare how toddlers and chimps revise beliefs.

It’s fascinating to design a task for chimps, and then try to adapt it for a toddler.

Dr. Emily M. Sanford.

Eventually, she hopes to extend the study to other primate species as well, building a comparative map of reasoning abilities across evolutionary branches. While Sanford has worked on everything from dog empathy to numerical cognition in children, one lesson remains constant: animals are capable of much more than we assume.
They may not know what science is, but they’re navigating complex environments with intelligent and adaptive strategies, and that’s something worth paying attention to.

Dr. Emily M. Sanford.

Other members of the research team include: Bill Thompson (UC Berkeley Psychology); Snow Zhang (UC Berkeley Philosophy); Joshua Rukundo (Ngamba Island Chimpanzee Sanctuary/Chimpanzee Trust, Uganda); Josep Call (School of Psychology and Neuroscience, University of St Andrews); and Esther Herrmann (School of Psychology, University of Portsmouth).

Publication:
Hanna Schleihauf et al.
Chimpanzees rationally revise their beliefs.
Science 390, 521-526 (2025). DOI:10.1126/science.adq5229

Abstract

The selective revision of beliefs in light of new evidence has been considered one of the hallmarks of human-level rationality. However, tests of this ability in other species are lacking. We examined whether and how chimpanzees (Pan troglodytes) update their initial belief about the location of a reward in response to conflicting evidence. Chimpanzees responded to counterevidence in ways predicted by a formal model of rational belief revision: They remained committed to their initial belief when the evidence supporting the alternative belief was weaker, but they revised their initial belief when the supporting evidence was stronger. Results suggest that this pattern of belief revision was guided by the explicit representation and weighing of evidence. Taken together, these findings indicate that chimpanzees metacognitively evaluate conflicting pieces of evidence within a reflective process.

Hanna Schleihauf et al.
Chimpanzees rationally revise their beliefs.
Science 390, 521-526 (2025). DOI:10.1126/science.adq5229

© 2025 American Association for the Advanvement of Science.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.

What this study ultimately highlights is a principle at the very heart of science: the willingness to change one’s mind when the evidence changes. Chimpanzees demonstrated this with ease, adjusting their expectations when presented with new information. Human children over the age of four typically do the same as their cognitive abilities develop.

Creationists, however, find themselves in a very different category. Their worldview demands that beliefs remain fixed regardless of contradictory evidence. Where science progresses through revision, correction, and refinement, creationism survives only by shutting the door on anything that might disturb its predetermined conclusions. In this sense, creationists fall behind not only the scientific community but also behind chimpanzees — and even toddlers — in basic rational responsiveness.

The contrast could not be clearer. When faced with new facts, chimpanzees update their beliefs; creationists update their excuses. The study’s findings serve as a reminder that the strength of science lies not in inflexible certainty but in the courage to revise, rethink, and improve our understanding of the world.

If humans evolved intelligence, why are there still creationists?