Roger was screaming for as he was being beaten up by a group of muggers on a street. there were about 15 people standing nearby. however, none of the bystanders came forward to roger. this scenario representing lack of illustrates:

This scenario of Roger being beaten up and not one of the 15 people actually helping Roger perfectly illustrates that which is called the diffusion of responsibility. This is a sociopsychological phenomenon that occurs when there is a group of people and it means that the person is less likely to help and take responsibility or irresponsibility, either one, when other people are present.