The bystander effect or bystander apathy

The bystander effect (or bystander apathy) is a social psychological phenomenon in which individuals are less likely to offer help to a victim when others are present. The higher the number of spectators, the less likely it is that is that any one of them will be able to help.

In a figurative way, if a person is attacked and hopes to be rescued, it is better that around there are one or very few people.

The probability of rescuing a person in distress is higher when the responder is alone than when he is in the presence of others. Either we don’t consider it our business or we think that others have already taken care of the situation.

Several factors contribute to the bystander effect, including the ambiguity, group cohesiveness and diffusion of responsibility that takes place among those present, and by the fact that the perception and reaction of bystanders are affected by the presence of others.

_{More on Wikipedia Effet du témoin (Fr), or Bystander effect (En)}