This experiment had to be stopped before the end of the time set aside as the people involved lost control of who they were. The "prisoners" truly became prisoners with the poor self-esteem, attempts to curry favor with the guards, and in general became very submissive. The "guards", who were given unlimited authority, became abusive to the prisoners, aggressive in their attitudes and actions, and began to lose sight of the experiment and become the abusive guards they never thought they would be. The why is to look at the dark side of human nature which we all have, and that absolute power corrupts. With no one to put controls on the behavior of the volunteer participants, the darkness of human behavior spiraled out of control, forcing the end of the experiment. No one had expected the results to be what they were including the people who had designed the experiment. The answer shed light on the abuse in prisons, concentration camps, war prisons etc. Absolute power corrupts almost everyone.