Chimpanzees (Pan troglodytes) can change the way they think when faced with new information, bringing them closer to rational human thinkers.
The conclusion comes from a recent investigation, published last week in the journal Science, in which researchers from the Netherlands, the United Kingdom and the United States argue that our primate cousins can alter their beliefs based on the information at their disposal, a key trait of rational thinking.
“Rationality is a distinguishing feature of human thought. Rational agents form beliefs about the world based on evidence, but as new evidence emerges, they revise their beliefs by weighing the strength of their previous beliefs against the strength of the new evidence,” the scientists explain in the article.
The work was conducted at a chimpanzee sanctuary on an island in Uganda’s Lake Victoria, Africa’s largest lake. The researchers presented the non-human primates with two boxes: one containing food and the other empty.
In an initial phase, the scientists suggested to the animals which of the boxes contained food. Subsequently, they suggested that the empty box was the one containing food. According to the study’s results, the chimpanzees frequently changed their choice based on the cues they were given. It may seem trivial, but the researchers say it provides evidence that chimpanzees are capable of rational thought.
“The chimpanzees were able to revise their beliefs when better evidence became available,” explains Emily Sanford, of the University of California, Berkeley and the study’s second author, in a statement.
“This kind of flexible reasoning is something we often associate with four-year-old children. It was exciting to show that chimpanzees are capable of this as well,” she notes.
The team says they used techniques and a methodology to ensure that the chimpanzees’ responses reflected actual rational choices and not merely instinct, for example by resorting to highly controlled experiments and computational models. The aim was to exclude notions that the chimpanzees preferred the more recent suggestions or reacted to suggestions as obvious.
“The models confirmed that the chimpanzees’ decision-making process aligned with rational belief-revising strategies,” state the scientists involved in the research.
The researchers say that this study challenges the notion that rational thinking is exclusive to humans, and the aim is to extend the study to human children and to other primate species.
