In the post Holocaust era, the question of how normal people could commit such horrid acts to one another haunted the American psyche. Like Stanley Milgram, Philip Zimbardo (1971), wanted to see how normal people could commit such horrid acts.
Therefore, Zimbardo decided to simulate a prison experience and see how people behaved when given roles of authority (“guards”) and how people reacted to this authority (“prisoners”). The experiment, which was supposed to last for 2 weeks ended after 6 days due to the profound psychological impact the experience had on the subjects. Simply put, the situation got to “real.”
This experiment is a disturbing example of how labels of authority can altar people. For additional facts about the experiment, see the following link http://www.prisonexp.org/