Apes know if you know

What do others know, what do they think and how will this affect their actions? Not only we humans can put ourselves in the minds of others, a behavioral study now makes clear: Apes also have the highly developed ability of the so-called “Theory of Mind”. The experiments show that the apes rely on their own experiences when it comes to their expectations regarding the knowledge and behavior of others.

Being able to empathize with others is a key element of our social behavior and our ability to cooperate. In many contexts it is important to have an idea of ​​what information, motives or errors our fellow human beings have in mind so that we can adjust accordingly. In psychology, this ability is called the Theory of Mind. For a long time, this complex intellectual achievement was considered a unique selling point of human beings. But this aspect also showed how similar the great apes are in many ways. Behavioral studies show that to a certain extent they can put themselves in the minds of others: they recognize their motives and understand what they know.

How far does the skill go?

In this context, the researchers led by Fumihiro Kano from Kyoto University were able to show in 2016 that great apes even understand that someone has to be wrong – that he believes in something that does not match reality. But as they explain, the test procedure used left questions unanswered as to how far the animal’s capacity for Theory of Mind extends in this regard. In their current study, the scientists have therefore confronted their experimental animals with an even more complex test system.

Chimpanzees, bonobos and orangutans took part in the experiments. First, the experimental animals were familiarized with two versions of a partition. Some were presented with a wall that was completely opaque – so it acted as a privacy screen. A second group, on the other hand, was shown a partition made of a slightly transparent material so that the animals could still see what was going on behind it. Knowledge of the respective properties of the partition should later play a role in the actual tests.

Glances reveal thoughts

In these experiments, the scientists presented the apes with a kind of theater scene. They recorded the eye movements of the animal viewers using eye trackers. As the researchers explain, the apes’ expectations are reflected in what they look at intensely: if they think that someone is about to grab a certain object, they look at it conspicuously often. In the case of the experimental scenes, these were two boxes that two actors were dealing with.

One demonstratively observed how the other actor hid an object under one of the two boxes. The observer then stood behind the partition known to the animals. Now the second actor secretly took out the genre from under the box, initially hid it under the second, but ultimately decided to take the object with him. After this secret action, the observer stepped out of his position behind the partition with the intention of getting the hidden object. The question now was: what expectations do the experimental animals have, under which crate would they look first? In other words: what do the monkeys believe, what does this person think

Own knowledge shapes expectations

As the researchers report, evaluations of the gaze patterns showed that, based on their knowledge and what they saw, the animals developed the same expectations that humans would. Those monkeys who had been introduced to an opaque partition assumed that the observer behind the screen had not seen that the other actor had secretly taken the object with them. As a result, this man followed the wrong assumption that the object was under the box that had acted as a hiding place when observed. The experimental animals stared exactly at this box when the actor wanted to get the object.

On the other hand, the animals that had learned that the partition is transparent showed a different way of looking. Apparently they assumed that in this case the actor had seen that the other actor had taken the object with him and thus knew that there was nothing to be found under both boxes. As the scientists explain, this was reflected in the fact that the monkeys paid no more or less attention to either of the boxes. They interpret this result as confirmation that the animals also rely on their own experience in their expectations regarding the knowledge and behavior of others.

“We were pleased that great apes actually passed this difficult test,” says Kano. “The results now show that we share the theory of mind ability with our evolutionary relatives. We are now planning to refine our methods to test further aspects of this ability in animals, ”said the scientist.

Sources: Kyoto University, technical articles: PNAS, doi: 10.1073 / pnas. 1910095116

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