Washington (AFP)

Rats are less likely to rescue a congener if members of their group passively attend the scene, according to a study that sheds new light on the so-called "spectator effect" or "witness effect".

For Peggy Mason, a neurobiologist at the University of Chicago and lead author of the experiment, the results can help better understand human behavior, especially that of police officers who do not intervene when a teammate engages in abusive violence.

The experiment, described in the American journal Science Advances on Wednesday, showed that a rat, when alone, generally helped another rat to free itself from a trap (a plastic box), and opened the door for it .

But when the researchers added to the scene two control rats and medicated with anxiolytics, the same rat did not intervene any more and left its congeneric blocked.

Conversely, when the control rats were not drugged, the rat was even more inclined to become a good Samaritan than when it was alone.

"This is a timely study," said Peggy Mason. "In the George Floyd case, there were three other police officers, including one who had become a police officer to change what was said about police brutality against black people, and yet he stayed by without intervening."

For the researcher, the police were not given medication like rats but had undergone similar conditioning, in the form of "years of training".

When a person does not help, "this person is not a bad sheep, it is a sheep among others", all subject to the innate rules of behavior of mammals. "We are programmed to do so".

The term spectator effect was coined by psychologists after the 1964 murder of Catherine (Kitty) Genovese in New York, which some thirty neighbors would have witnessed without intervening. In reality, several had intervened, but the concept continued, and was verified by experiments in which humans were surrounded by passive witnesses.

A scientific article by Richard Philpot published in the journal American Psychologist last year showed that in reality, in the real world (and not as in old human experiences), the witnesses of a scene intervened most of the time. His study reviewed more than 200 violent incidents recorded by surveillance cameras: in nine out of ten cases, people intervened.

The new experiment on rats is consistent with this study by Richard Philpot because it shows that the rat's desire for mutual aid is magnified by the presence of helping witnesses.

Peggy Mason's team believes that in humans, as in rats, altruism is linked to the internal reward circuits of the brain, and not to a notion of which, among many people, is believed to be responsible.

© 2020 AFP