Human beings are not the only ones capable of intuitions, like guessing that a fellow man of ours will go looking in the place where he saw that an object has been hidden, even if then we were witnesses that he was removed from there. To share this ability with us, which children from the age of four, and perhaps even earlier, have, are also chimpanzees, bonobos, orangutans.

I see you're wrong. It might seem trivial, but to be endowed with a theory of the mind, that is to be able to attribute to others desires, intentions, beliefs, even false beliefs such as that of looking into the hiding place that we know is wrong, has long been considered the distinction that we separates from other primates.

Researchers studying animal cognition have observed some traits of intelligence and understanding of the mind of others, so far considered typically human, even in other animals. In some experiments, for example, chimpanzees have proved capable of deceiving comrades, or of remembering who had been a good companion in carrying out a task.

Image Do other primates share a theory of mind with man? | Eric Isselée

But until now it has not been possible to find convincing proof in other primates of the ability to attribute to other false beliefs, one of the most sophisticated elements of a theory of mind. This is also because it is not easy to set up experiments to prove it, given that food is often present in tests, useful for involving animals but also an element of distraction, or because they are often based on an understanding of language.

Soap opera for monkeys. A group of primatologists has devised a system to overcome these obstacles, setting up an experiment that makes use of a video created specifically for animals, and eye-tracking technology, which allows us to precisely follow the movement of the gaze, and therefore the points in which the animal's attention is concentrated.

For the video, an international group of researchers set up a sort of soap opera that could attract the interest of the "volunteers" of the studio, and created two different "episodes". In the first, an actor disguised as a monkey (nicknamed King Kong) engages in a sort of struggle with a human being, and then goes into hiding under one of two straw sheaves, while the man does not look. In the other, King Kong himself, in a cage, steals a stone from a visitor, hides it under a box, moves it under another, and finally takes it away while the man has moved away.

Image Collective relaxation. | Fiona Rogers / Nature Picture Library / contrast

In both cases, the human figure that has moved away re-enters and goes in search of King Kong under the sheaf, or of the stone in the box.

The videos were shown to 19 chimpanzees, 14 bonobos and 7 orangutans, and the majority of the animals at the end of the video - the return of the human being - fixed his gaze at the point where he "knew" that the actor would go watching. In a similar percentage to what happens with children aged two or over with whom similar experiments have been done, these primates have been able to understand that the information in their possession did not coincide with that of the person in the video, and have correctly awaited the conclusion of the story.

This ability - the primatologist Frans de Waal wrote in a commentary accompanying the article published in Science (abstract in English) - «has probably evolved in the complex hominid societies (human beings and primates) to offer individuals the benefit of better anticipate the behavior of others ". And it is important to study its biological origins and evolution also to better understand the disorders in which the theory of the mind does not seem to have formed correctly, for example autism .