The purpose of this essay is to understand the development of norms and the effects of roles, labels, and social expectations in a simulated prison environment. There were many results, but perhaps the most important was simply this: The simulation became so real, and the guards became so abusive, that the experiment had to be shut down after only 6 days rather than the two weeks planned. the study was approved by the Stanford Human Subjects Review Committee, the Stanford Psychology Department, and the Group Effectiveness Branch of the Office of Naval Research. In addition, the Student Health Department was alerted to the study and prior arrangements were made for any medical care the participants might need.