Bystander effect
Individuals are less likely to offer help to a victim when there are other people present.
Cause
When confronted with a potential emergency, people typically play it cool, adopt a look of nonchalance, and monitor the reactions of others to determine if a crisis is really at hand. However, because each individual holds back, sometimes everyone concludes that the situation is not an emergency and hence does not require intervention.
Consequences
Some parts of the world have included laws that hold bystanders responsible when they witness an emergency.