If one of his mates is in trouble, a rat helps him, even at the cost of giving up something he really likes: a piece of chocolate.

It is the observation of a behavior that to all intents and purposes we would tend to define altruistic made by a group of Japanese researchers and reported in the journal Animal Cognition.

The debate has been going on for a long time if altruism and empathy, the "feeling" that it underpins, are a characteristic only of human beings (even if often the facts of the news sadly lead to wonder how much is really universal in our species) or if they are a trait that has developed in the course of evolution, and that therefore also belongs to other animals, primates or mammals.

Animal generosity. Several studies have shown behaviors that we would not hesitate to define as intentional help to another member of the species, but the interpretation of experiments or observations in nature has also often been questioned. At times, a "selfish" motivation for apparently altruistic behavior has been identified, for example that of a group of young crows that attract other companions to feed on the food found, not out of generosity, but in a way that is more unlikely for them to come attacked by other individuals that dominate the territory.

The macaque that revives the friend (in English - 1:05)

In this video, taken in a train station in India, a macaque "revives" a similar one who was struck.

Altruists or companions? Rats and mice are animals for which altruistic behavior has been suggested several times. For example, in a study a few years ago, the behavior of rats that helped, apparently without any "noble" motivation, a trapped comrade had already been observed. The animal - however, was the objection - does it not because it is pity, but because it instinctively prefers to stay in the company of its fellows. The new experiment would seem to overcome this very objection.

Dilemma for mice. Researchers at Kwansei Gakuin University in Japan placed the animals of their experiment in a box with two compartments divided by a transparent wall (here the video): on the one hand a rat was placed in a pool of water, forced to swim to keep floating; on the other, one of his companions had the chance to get him out of the water by opening a small door.

Image The rats used in the experiment. | Sato N. et al, Animal Cognition (2015)

Most of the animals, properly trained, chose to open the small door and - which in turn suggests - the rats that had already experienced the same situation were faster to do so, ie they were in turn immersed in the pool . The most surprising thing, however, was that, even when faced with the choice of whether to open the door that freed the companion in difficulty, or another small door that gave access to a prize, a piece of chocolate, in most of the cases (up to eighty percent) the animals chose to help the mate first.

Is altruism part of our biology? That's what some researchers think.