The Stanford Prison Experiment was based on a true story of a shocking human behavior study in 1971. Twenty-four university students volunteered to participate in the experiment conducted by Dr. Philip Zimbardo, a psychologist interested in studying violent behavior in prisons. The volunteers were divided into guards and prisoners within a simulated prison. The results were astonishing, as ordinary people began to exhibit sadistic behavior, while others started to show signs of psychological distress after just a few days of the experiment.