The following links feature very important concepts in social psychology. Review Asch's, Milgram's and Zimbardo's classic studies and read up on the "bystander effect."
The Bystander Effect... what would you do?
This just happened, so all the facts aren't in yet but it looks like a 31 year-old Guatemalan man named Hugo Alfredo Tale-Yax was stabbed on the street in New York City and many pedestrians walked right past him as he died. You can read the story and see a surveillance video here.
Read more about the bystander effect here.
Solomon Asch's conformity study showed how easily people will give an obviously wrong answer when other people are giving that same answer. Watch the video at the link below:
Stanley Milgram's obedience study was recently partly replicated by ABC's Prime Time show. Watch how easily people follow orders even when they know the orders are wrong.
Zimbardo's Prison Roles
Philip Zimbardo's experiment about how roles affect behavior is known as the "Stanford Prison Experiment." Those playing inmates became passive while those playing guards became aggressive. Subjects' real identities seemed to pale in comparison to the roles they played so much that the experiment had to be stopped after a few days. Who knows what would have happened if the experiment had gone on for two full weeks.