This article is about the psychological phenomenon. For the bystander effect in radiobiology, see Bystander effect (radiobiology).
The bystander effect or Genovese syndrome is a social psychological phenomenon that refers to cases where individuals do not offer any means of help in an emergency situation to the victim when other people are present. The probability of help has often appeared to be inversely related to the number of bystanders; in other words, the greater the number of bystanders, the less likely it is that any one of them will help. The mere presence of other bystanders greatly decreases intervention. In general, this is believed to happen because as the number of bystanders increases, any given bystander is less likely to notice the situation, interpret the incident as a problem, and less likely to assume responsibility for taking action.