Stanford Prison Experiment

This infamous Stanford Prison Experiment has etched its place in history, as a notorious example of the unexpected effects that can occur when psychological experiments into human nature are performed.

Like a real life ‘Lord of the Flies', it showed a degeneration and breakdown of the established rules and morals dictating exactly how people should behave towards each other.

The study created more new questions than it answered, about the amorality and darkness that inhabits the human psyche.

As a purely scientific venture, the experiment was a failure, but it generated some results that give an insight into human psychology and social behavior. The ethical implications of this study are still discussed in college and undergraduate psychology classes all across the world.

In the days of the Abu Ghraib and Guantanamo abuses, the Stanford Prison Experiment is once again becoming relevant, showing that systematic abuse and denial of human rights is never far away in any prison facility.

This study is so well known that a Hollywood movie about the Stanford Prison Experiment is going to be released in 2009. The experiment has also been the basis of many similar studies, over the years, but these have had much stricter controls and monitoring in place.


In 1971, the psychologist Philip Zimbardo tried to show that prison guards and convicts would tend to slip into predefined roles, behaving in a way that they thought was required, rather than using their own judgment and morals.

Zimbardo was trying to show what happened when all of the individuality and dignity was stripped away from a human, and their life was completely controlled.

He wanted show the dehumanization and loosening of social and moral values that can happen to guards immersed in such a situation.


To conduct the Stanford Prison Experiment, Zimbardo constructed a mock correctional facility in the basement of Stanford University.

Adverts were placed in local newspapers offering $15 per day for participants in this program. Of the 75 responses, the 24 male subjects judged to be most mentally and emotionally stable were selected. Mainly middle class and white, they were divided into two groups randomly, of 12 prisoners and 12 guards.

The group selected to be the guards were outfitted in ‘military-style' intimidating uniforms. They were also equipped with wooden batons and mirrored shades, to prevent eye-contact and make the guards appear less human.

In an initiation meeting, Zimbardo, who acted as the warden for the duration of the experiment, informed the guards that the only rule was that no physical punishment was allowed. Other than that, the guards were to run the prison as they saw fit, and would be divided into regular working shifts and patterns.

Prisoners, by contrast, were dressed in cheap smocks and were allowed no underwear. They were to be addressed by, and answer to, identity numbers only. They also had a small chain around one ankle to remind them that they were inmates in a correctional facility. Conditions were tough, with only basic sleeping mattresses and plain food being supplied.

The prisoners were instructed to wait at home "to be called" for the start of the experiment; their homes were raided without any warning, arrested by the real local police department and charged with armed robbery.

The Palo Alto Police had agreed to help with the experiment. As if they were real-life suspects, the prisoners were read their rights and had their mug shots and fingerprints taken. After being stripped, searched and de-loused, they were taken into the cells that would be their homes for the next two weeks.

Zimbardo, acting as a prison warden, would be able to observe and make notes about what happened during the course of the study.


The Stanford Prison Experiment degenerated very quickly and the dark and inhuman side of human nature became apparent very quickly.

The prisoners began to suffer a wide array of humiliations and punishments at the hands of the guards, and many began to show signs of mental and emotional distress.

On the second day of the experiment, the prisoners organized a mass revolt and riot, as a protest about the conditions. Guards worked extra hours and devised a strategy to break up and put down the riot, using fire-extinguishers.

No prompt for this action was given by Zimbardo; the guards used their own initiative to formulate the plan.

Standard prisoner counts and roll-call became a trial of ordeal and ritual humiliation for the prisoners, with forced exercise and physical punishments becoming more and more common. Mattresses were confiscated from the prisoners and they were forced to sleep on cold, hard floors.

Toilet facilities became a privilege, instead of a basic human right, with access to the bathroom being frequently denied; the inmates often had to clean the toilet facilities with their bare hands. Prisoners were often stripped and subjected to sexual humiliation, as a weapon of intimidation.

The experiment showed that one third of the guards began to show an extreme and imbedded streak of sadism, and Zimbardo himself started to become internalized in the experiment. Two of the prisoners had to be removed early because they were showing real signs of emotional distress.

Interestingly, none of the prisoners wanted to quit the experiment early, even when told that they would be denied their participation pay. The prisoners became institutionalized very quickly and adapted to their roles.

A replacement prisoner was introduced and was instructed to go on hunger strike as a protest about the treatment of his fellow inmates, and as an attempt to obtain early release. Surprisingly, his fellow inmates viewed him as a troublemaker rather than a fellow victim trying to help them.

When the inmates were informed that, if the rest of their prisoners gave up their blankets, he would be released from solitary confinement, all but one refused to give up their blanket.

The Stanford Prison Experiment carried on for six days until an outsider, Christina Maslach, a graduate student who would later become Zimbardo's wife, was brought in to interview guards and prisoners and was shocked by the scenes that she was witnessing.

Zimbardo terminated the experiment early and noted that out of over 50 external visitors, this lady was the only one to raise concerns about what was happening.


Zimbardo believed that the experiment showed how the individual personalities of people could be swamped when they were given positions of authority.

Zimbardo has acknowledged that some guards did try to change the system. He later investigated the topic about "heroes" - those who do not succumb to the system.

Social and ideological factors also determined how both groups behaved, with individuals acting in a way that they thought was required, rather than using their own judgment.

The experiment appeared to show how subjects reacted to the specific needs of the situation rather than referring to their own internal morals or beliefs.

The results of the experiment have been used in many high profile court cases over the years, to try and show that a prison must have clear instructions and guidelines from higher level authorities, or prisoner abuse may occur.


The ethics of the Stanford Prison Experiment have long been called into question, and, certainly, without stricter controls this experiment would not be sanctioned today; it could pose a genuine risk to people disposed towards mental and emotional imbalances.

In fairness to Zimbardo, most of these discussions take place with a lot of hindsight, and he could not have guessed the internalization and institutionalization that would occur during the course of the study.

Other criticisms include the validity of the results. It was a field experiment, rather than a scientific experiment, so there are only observational results and no scientific evaluation.

In addition, it would be very difficult for anybody to replicate the experiment conditions.

The selection of the subjects has been questioned extensively with the wording of the advert stating ‘wanted for prison experiments', this may have caused people with more of a pre-disposition towards violence to apply.

In the aftermath of the study, many of the guards and prisoners indicated that they were only acting out roles that they thought were expected of them, so there is no consensus on whether the study really portrayed human nature or not.

Whether the Stanford Prison Experiment relates to real prisons is another matter. Although maltreatment of prisoners undoubtedly takes place all across the world, in most facilities, the guards are carefully screened and undergo a long and extensive training process. Zimbardo screened both prisoners and guards for non-social tendencies in his experiment.

They also have rigid protocols to which they are supposed to stick. In addition, the study studied only male subjects and most western prisons do have a mix of sexes on the guard staff.

Zimbardo also glossed over the fact that not all of the guards showed sadistic tendencies, with some seeking to actively help the prisoners and show sympathy towards them.

Later studies have concluded that abuse in prisons often comes from the top down and that when orders are given these can affect the results. If the guards had been given stricter guidelines from Zimbardo at the beginning then there may have been fewer sadistic tendencies shown by the guards selected for the Stanford Prison Experiment.

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How to cite this article: 

(Jun 22, 2008). Stanford Prison Experiment. Retrieved Oct 02, 2015 from

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