What is the bystander effect and what causes it?

The bystander effect is the tendency for individuals to be less likely to help someone in distress when other people are present. Research by John Darley and Bibb Latane showed that as the number of bystanders increases, the probability that any one person will help decreases. Two psychological processes explain this: diffusion of responsibility, where each person assumes someone else will help, and pluralistic ignorance, where each bystander looks to others for cues about how to react and misinterprets their inaction as evidence that help is not needed.