The Bystander Effect refers to the likelihood of getting help in an emergency situation decreasing with the number of additional people present.

Individuals feel less responsibility with more people involved

Supporting Experiments - Latané & Darley

Participants sit in a room whilst it fills with smoke (1970)

• 1 participant - gets help fast, and 75% of the time
• 3 participants - they get help 38% of the time, slowly
• 3 participants - 2 of them research assistants who notice and do nothing - the 1 other gets help 10% of the time

Talking about campus life over intercom (1968)

2-5 participants would sit in rooms by themselves and have a conversation about campus life. 1 of them (a recording) would have a seizure: