They were not real suspects but a couple of students who had answered a local newspaper advertisement looking for volunteers in a study of the psychological effect of prison life. They wanted to figure out what the psychological effect were of becoming a prisoner or prison guard. Therefore, they set up a simulated prison and then carefully note the effects of this institution on the behavior of all people invovled in the walls.

It was surprising that more than 70 candidates applied this job and they were given diagnostic interviews and personality tests to rule out candidates with psychological problems, mental disabilities, or a history of crime or drug abuse. Ultimately, there was a sample of 24 students from US and Canada who happened to be around Strandford area and wanted to earn $15  per day by taking part in the study.

'Our study of prison life began with an average group of healthy, intelligent,middle-class males. These boys were arbitrarily divided into two groups by a flip of the coin. Half were randomly assigned to be guards, the other to be prisoners. It is important to remember that at the beginning of our experimentthere were no differences between boys assigned to be a prisoner and boys assigned to be a guard.'- by Philip