Rats, like people, are less inclined to help relatives, if there are other individuals of their species, theoretically capable of help, it is reported in Science Advances. This phenomenon is called the bystander effect, and so far it was found only in Homo sapiens. However, in rodents in the first place has a value the behavior of the witnesses, not the mere fact of their presence. If everyone else is passive, even those who are able to help, do nothing to rescue the victim, and if there are active witnesses, the animal is in trouble are most likely to help.
Since the late 1960s, psychologists say about the bystander effect: if only one person saw that someone was in trouble, he is more likely to provide assistance than in the case when apart from him at the scene will be several witnesses. Although it was later revealed that, in General, people are willing to help the victims and the presence of other able to help (and the more active witnesses, the higher the probability that they will help), the phenomenon is important for understanding human group behavior. In addition, until now, the bystander effect nor in any other species except Homo sapiens, is not found.
Peggy Mason (Peggy Mason) from the University of Chicago and her colleagues chose a seemingly unusual object for the study of bystander effect of male gray rats (Rattus norvegicus) of two lines: the Spreg-doli and long-Evans. However, the rat — one of the most intelligent of rodents they are willing to help each other, so the probability to detect they have the effect of a witness nonzero.