What is a Bystander? What is the Bystander Effect?
A bystander is any person who is present at an event or incident but does NOT take part.
The bystander effect is when multiple people are witnessing a problematic situation, but no one does anything about it because they assume someone else will help. This results in the Diffusion of Responsibility, or no one taking responsibility for doing something to help. (Fischer et al. 2011 The Bystander-Effect)