"The Lucifer Effect: Situations create Evil"
In 1971, Philip Zimbardo turned a Stanford basement into a mock prison. Healthy students were randomly assigned as Guards or Prisoners. The experiment was meant to last two weeks but was stopped after 6 days. The guards became sadistic and abusive, while the prisoners suffered emotional breakdowns.
This study demonstrated the power of the situation and social roles over individual personality. Good people can turn evil if placed in a toxic system that dehumanizes others. It is often cited to explain abuses in real prisons like Abu Ghraib.