Philip Zimbardo and his co-workers at Stanford University were interested in determining the causes of the dehumanization that is so prevalent in prisons. Suppose the ordinary members of society were persuaded to act as guards and prisoners in a mock prison which mimicked the environment and day-to-day running of the actual prison? If the mock prison failed to produce the hostility and alienation of a real prison, this would surely suggest that the personality characteristics of the guards or the prisoners, or both, are the vital ingredients in the unpleasantness found in a real prison. On the other hand, if the behavior observed in the mock prison was very similar to that in a real prison, this would suggest that it is the environment of a prison which is the crucial factor in producing unpleasantness.

The experiment started on August 14, 1971, in Palo Alto, California. The quiet Sunday morning was shattered by a screeching squad car siren as police swept through the city picking up the participating college students from their homes in a surprise “mass arrest”.

(1)  All of the “suspects” were charged with a felony, warned of their constitutional rights, spread-eagled against the police car, searched, handcuffed, and taken away in the back seat of the police car to the police station. The whole operation was carried out so realistically, thanks to the cooperation of the Palo Alto City Police Department, that the alarmed mother of one 18-year-old student arrested for armed robbery exclaimed: “I felt my son must have done something: the police have come to get my son!”

On arrival at the police station, each suspect was fingerprinted and identification forms were prepared for his “jacket” or central information file. He was then left on his own in a detention cell. Later in the day, each suspect was blindfolded and taken to the “Stanford County Prison”, where he was stripped naked, skin-searched, deloused, and issued with a uniform, bedding, and basic supplies. The uniform worn by the prisoners consisted of a loose-fitting muslin smock with an identity number on the front and back, no underclothes, a light chain and lock around one ankle, rubber sandals, and a cap made from a nylon stocking.

The prison warden gathered the prisoners together, and told them about the 16 basic rules of prisoner conduct, starting with “Prisoners must address the guards as “Mr. Correctional Officer’, and ending with ‘Failure to obey any of the above rules may result in punishment’.”

The “guards” had been told beforehand that their task was to “maintain the reasonable degree of order within the prison necessary for its effective functioning”.

(2) They were given  only minimal guidance about the away they were expected to behave.

 (3) Except that they were specifically prohibited from using physical aggression. They were clearly distinguishable from the prisoners by their  uniform.

(4)  Which consisted of plain khaki shirts and trousers, a whistle, a police nightstick, and reflecting sunglasses.

The guards and prisoners were selected from among a total of 75 respondents to a newspaper advertisement asking for male volunteers to participate in a psychological study of “prison life” for 15 dollars a day over a period of two weeks.

(5) The 10 prisoners and 11 guards who actually took part in the experiment were among those respondents judged to be the most stable (physically and mentally), the most mature.

(6) And the least inclined towards anti-social behavior. In fact, the majority of them were middle-class students.

The prisoners and guards were to live within the confines of the “Stanford County Prison”, which was situated in the basement of the psychology building at Stanford University.

(7) This mock prison was deliberately designed to be as unpleasant as possible. There were three small cells (9ft. by 6ft., with three prisoners assigned to each.

 (8) As in a real prison, the windows were barred, and in addition to guards there was a warden, a superintendent (Zimbardo), a parole board, and a grievance committee. All participants had agreed to take part in spite of having been told that those assigned to play the prisoner role could expect to be:

(9) under surveillance,

(10) might be harassed, and might have

(11) some of their basic rights curtailed during imprisonment.