Washington (AFP)

The next time you come across a rat in your home, tell yourself that he may just want to play hide and seek.

For an experiment, a team of German neuroscientists spent several weeks with rodents in a small room filled with cartons. They discovered that the animals were surprisingly adept at the game, even though they were not rewarded with any candy.

Instead, the rats seemed sincerely happy to discover their human companions or to be caught by them, judging by the small leaps of joy and the ultrasonic cries they uttered, inaudible to the human ear and whose previous work has shown that they are associated with well-being.

The study, published Thursday in the journal Science, is not a cute story (or agonizing, depending on the point of view), because it gives a new perspective on the game, an important evolutionary trait in mammals.

"When you work a lot with rats over the years, you realize how intelligent and social these animals are," says co-author Konstantin Hartmann of the Humboldt University in Berlin, where the other members are also based. 'team.

"But it was a surprise to see how well they were doing," he added to AFP.

The recruits were adolescent male rats, and the playground a room of 30 square meters. A researcher crouched to hide behind a cardboard, or gave the rat a head start to hide, the human looking for him.

For one to two weeks, the rats learned that starting the game inside a closed box, then open at a distance, meant that they had to search, while starting the game with the open box meant that they had to to hide.

- Ethical issues -

They quickly developed relatively sophisticated strategies, such as revisiting places where humans had previously hid, or sheltering in opaque boxes rather than being transparent when they were hiding.

To train them, the authors rewarded the rats not with food or water, which would have invalidated the experiment, but with a positive social interaction, in the form of a physical contact.

"They are looking for our hand, we tickle the ribs, it's a bit like playing with kittens or puppies," says Konstantin Hartmann.

Scientists believe that rats were motivated not only by these interactions, but that they also liked the game itself.

In addition to shouting and jumping for joy, the rats jumped and went away when they were found, as if they wanted to prolong the play and delay the reward.

Play has an important role in the cognitive development of adolescent mammals.

Rats are an ideal model for studying brain activity in humans because of their evolutionary proximity, which also explains their frequent use in medicine.

Scientists would like to know which parts of the prefrontal cortex, related to social behaviors, are involved - but since play is a fluid activity, it is difficult to study.

As a result, the team attached microfilars to the head of the rats recording their brain activity, allowing them to identify the neurons associated with specific gaming events. This could someday be used for future studies: for example, to examine neuronal development when gambling activities are restricted during adolescence.

All this raises ethical questions about the use of rats in scientific and medical experiments.

"It's very important to be aware of the cognitive abilities of an animal," says Konstantin Hartmann, adding that the scientific interest of experiments must always be weighed against the use of animals.

"This type of research will help scientists see rats as more than mere objects of experience."

© 2019 AFP