People are less likely to help someone in an emergency when more bystanders are present.

Across decades of research, one of the most consistently replicated findings in social psychology is that an individual’s likelihood of helping someone in distress goes down as the number of other bystanders present goes up. This runs counter to the intuitive assumption that more people around should mean help is more likely to come from someone.

Researchers attribute the effect largely to diffusion of responsibility: when many people witness the same emergency, each individual feels less personally obligated to act because responsibility is spread across the group, and people also look to others’ reactions to judge whether a situation is actually serious. The effect has been demonstrated in a wide range of settings, from staged emergencies in laboratories to analyses of real-world helping behavior, and understanding it is part of why safety training often teaches people to single out one specific bystander and directly assign them a task, like calling for help, rather than shouting for help in general.