What does the "bystander effect" describe?

The bystander effect describes the finding that an individual is often less likely to help someone in distress when other people are present, compared to when alone. The commonly proposed explanation involves diffusion of responsibility, each bystander assumes someone else will step in or has already called for help, which paradoxically makes a larger crowd less likely to act.

The idea that crowds make wiser decisions or that people simply copy strangers' clothing describes different phenomena entirely, unrelated to the finding about helping behavior, and neither captures the core dynamic of responsibility being diffused across onlookers.

Awareness of the bystander effect has practically useful implications, some safety training now teaches people to counteract it by pointing directly at a specific individual and assigning them a task, such as 'you, call for help,' which breaks the diffusion of responsibility and makes it much more likely someone actually responds.