A study published on October 30, 2025, in the journal Science shows that chimpanzees, our closest evolutionary relatives, have the ability to change their minds and make new choices according to the evidence and circumstances experienced. This ability, broadly speaking, is the basis of what we can call rational thinking – which until now was classified as a distinctive characteristic of human beings.

The new finding is that the results of this study, conducted by Dutch scientists with chimpanzees at the Ngamba Island Sanctuary, in Uganda, provide strong support for the view that chimpanzees have genuine metacognitive capacities (reflecting on their own thinking).

“I think we have the evidence that we can say, okay, no, rationality in its fundamental form is not uniquely human, but we also share some basic processes of this with chimpanzees”, told Hanna Schleihauf, a psychologist at Utrecht University and one of the study’s authors, to the New York Post. 

The study conducted a total of 5 experiments based on the Bayesian statistical model for rational thought revision. Below there is the description of the first two experiments (image). For more details, see the study’s publication in Science – https://www.science.org/doi/10.1126/science.adq5229

Fig. 1. Procedure of Experiments 1 and 2.

1. Experiment 1, (A) Weak evidence first condition: Chimpanzees first received weak evidence (auditory evidence: shaking the box with a piece of wood in it) for one of the boxes and made a first choice. Then they received strong evidence (direct visual evidence: seeing into the box through a glass pane) for the other box and made a second choice. Strong evidence first condition: The same types of evidence were presented but in reverse order. (B) Experiment 2, Weak evidence first condition: Chimpanzees first received weak evidence (indirect visual evidence: seeing traces of the food behind the box) for one of the boxes and made a first choice. Then they received strong evidence (auditory evidence: shaking the box with a plastic capsule containing peanuts in it) for the other box and made a second choice. Strong evidence first condition: The same types of evidence were presented but in opposite order. Note: The red arrows indicate that the box was rotated (Experiment 1) or moved to the side (Experiment 2) to reveal visual evidence. In Experiments 1 and 2, in addition to the weak evidence first condition and the strong evidence first condition, chimpanzees also participated in filler trials, during which they received one piece of evidence, made a single choice, and received the contents of the box that they picked on their first choice (there was no second piece of evidence and no second choice). Filler trials were included such that subjects could not, on any given trial, predict whether their first or second choice would count.