In the post Holocaust era, the question of how normal people could commit such horrid acts to one another haunted the American psyche. Stanley Milgram decided to investigate this occurrence, in what turned out to be one of the most famous modern psychology experiments in history.
Milgram wanted to see if normal people would comply if authority figures told them to do inhuman acts. To do this, he set up a scenario where his subjects would think that they were giving escalating shocks to a person to the point where it could be lethal. The only prodding these subjects would receive to continue giving higher voltage shocks was from an authority figure in a white lab coat telling them that they must continue with the experiment.
The results of his experiment (which are summarized here http://www.age-of-the-sage.org/psychology/milgram_obedience_experiment.html) were disturbing, because the majority of subjects did continue to “shock” someone until the lethal levels when prodded by the authority figure.
The video records of Milgram’s experiments are a must see!