The ability to take on the emotions of one's fellows is not a human exclusive: which animal species do best to us? Among the primates, probably the bonobos (Pan paniscus).

According to a study published in Proceedings of the National Academy of Sciences, these cousins ​​of the hominid family react faster than other great apes to the emotions of their peers, especially when there are positive social behaviors like grooming or sex at stake.

The test. Researchers at the University of Leiden (Netherlands) came to this conclusion thanks to the dot-probe task, a psychological investigation tool used to measure emotional attention. During the experiment, animals are presented with neutral images or with various types of emotions; the photo is then replaced by the design of a point, which the subjects must touch to receive a reward. The speed with which the animals perform the operation is an indication of the attention they were devoting to the previous photo.

Positive contagion. The bonobos, compared to chimpanzees, orangutans and gorillas, showed a more rapid response to the emotional images depicting other bonobos: the spy of the ability to empathize with their own kind. The effect appeared more marked with images depicting protective or "group" behaviors such as grooming, mating and infectious yawning; less interest was given to photos of stressful or aggressive situations.

Similarities. Like humans, bonobos live in large groups in which social cohesion is indispensable for survival: hence the need to empathize with behaviors that favor interaction between peers. The situations that have aroused greater empathy are all protective or conducive to group bonds: the yawn cools the brain and increases alertness; sex and grooming cement the group (the bonobos, not surprisingly, are the only primates besides the man to have "frontal" sexual relations and to kiss with the tongue).

The discovery also confirms some neuroanatomical peculiarities: compared to other monkeys, bonobos have more gray matter in the amygdala and in the insula, brain structures linked to the control of emotions.