Probably the most famous of all experiments in the modern history of psychology is the Stanford prison study back in 1971. This situation put human behavior under a microscope. Led by Philip Zimbardo, a psychologist, a team of researchers and students set up the basement of Stanford Psych building as a mock prison. Total of 24 undergraduate students were selected and none of them had any prior criminal records, were tested for abnormal behavior and deemed to be perfectly normal. Some of them would play the role of guards, others the role of prisoners. Researchers left them alone and silently observed.
The prisoners stayed within their cells for 24 hours of the day whereas guards got to rotate their shifts every 8 hours. None of the undergraduates were aware that they were being filmed. The experiment should have gone on for six weeks however, it had to be curtailed in only six days because the guards became abusive towards the prisoners. They would often engage in psychological torture and the prisoners in turn displayed extreme anxiety, emotional stress and psychological pain.
Gradually, the guards began escalating their aggression towards all prisoners, sometimes stripping them naked, putting bags on their heads and the final straw was when they forced prisoners to engage in humiliating sexual activities. According to Zimbardo, it took only six days to turn 24 perfectly healthy (both physically and mentally) adults into the worst of society. It came to a point where the silent observers were worried about the guards, if they were left unsupervised.