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Craig Haney, Curtis Banks & Philip Zimbardo (1973)
Updated: 14 January 2013
AIMS: This study was funded by the US Navy, as it and the US Marine Corps were interested in investigating the causes of conflict between guards and prisoners in naval prisons. However, there was general concern about violence in civilian prisons too and, in particular, attacks by guards upon prisoners.
Attempts to explain the violent and brutal conditions often found in prisons had previously used dispositional attribution. That is, problems were due to the nature of the prison guards and the prisoners. It had been argued that prison guards bring to their jobs a particular ‘guard mentality’ and, thus, are therefore attracted to the job as they are already sadistic and insensitive people. Whereas prisoners are have no respect for law and order and bring this aggressiveness and impulsivity to the prison.
Philip Zimbardo was interested in testing this dispositional hypothesis by demonstrating that conditions in the prisons were not due to the type of individuals working and incarcerated in the prisons but could be best explained using a situational attribution. In particular he believed that the conditions were influenced by the social roles that prisoners and prisoner guards are expected to play.
In August 1971 Zimbardo set out to show that people allocated to be ‘prison guards’ or ‘prisoners’ would tend to slip into those predefined roles, behaving in a way that they thought was required, rather than using their own judgment and morals.
Zimbardo hoped the knowledge gained could be applied to real-
Introductory overview of the Stanford Prison Experiment
PROCEDURE (METHOD): The study is usually described as an experiment with the independent variable being the conditions the participants are randomly allocated to: either prisoner or guard. The dependent variable is the resulting behaviour. The study can also be described as a simulation as it was attempting to create a prison like environment.
Data collected were combinations of both quantitative and qualitative data. The main data though was qualitative and was obtained using video, audiotape and direct observation (both covert and overt).
The participants were respondents to a newspaper advertisement, which asked for male volunteers to participate in a psychological study of ‘prison life’ in return for payment of $15 per day. The 75 respondents completed a questionnaire about their family background, physical and mental health, prior experiences and attitudinal tendencies with respect to psychopathology and any involvement in crime.
Based on the results of the tests 24 men were selected. These 24 were judged to be the most physically and mentally stable, most mature, and least involved in antisocial behaviours. The participants were described as “normal, healthy male college students who were predominantly middle class and white”. The 24 participants did not know each other prior to the study.
A simulated prison was built in the basement of the psychology building at Stanford University. The simulated prison comprised:
A small, enclosed room, which was used as a ‘prison yard’.
Video recording equipment was placed behind an observation screen
For the duration of the study 9 ‘prisoners’ were to remain in the mock prison for 24 hours. 3 were to be arbitrarily assigned to each of the 3
cells; the other participants nominated ‘prisoners’ were to be on stand-
The participants all agreed voluntarily to play the role for $15 a day for up to 2 weeks. The participants signed a contract guaranteeing basic living needs, such as an adequate diet and medical care. Although it was made explicit in the contract that, if they were to be assigned to the role of prisoner, they would have to have some basic civil rights (eg: privacy) suspended. The participants were not given any information about what to expect or how to behave.
The 24 participants were randomly assigned by the flip of a coin to the role of ‘prisoner’ or ‘guard’ and informed by telephone to be available at their homes on a particular Sunday when the experiment would begin. (Interestingly, all the participants expressed the preference to become ‘prisoners’.)
Those participants allocated the role of guards had to attend an orientation meeting the day before the induction of the prisoners. They met the principal investigators, the ‘superintendent’ of the prison (Zimbardo) and the ‘warden’ (an undergraduate research assistant). They were told that the “experimenters wanted to try to simulate a prison environment within the limits imposed by pragmatic and ethical
Their assigned task as prison guards was to enforce 16 rules to ensure “a reasonable
degree of order” -
The guards were instructed in their administrative details, including the work-
The guards believed that the experimenters were mainly interested in studying the behaviour of the prisoners although the experimenters
were just as interested in their behaviour.
The uniforms of both prisoners and guards were intended to increase group identity and reduce individuality within the two groups.
The guards’ uniform consisted of a plain khaki shirt and trousers, a whistle, a police night stick (a wooden batton) and reflectingsunglasses to make eye contact impossible. The guards’ uniforms were intended to convey a military attitude while the baton and whistle were symbols of control and power.
The prisoners’ uniform consisted of a loose-
On the chosen Sunday morning the 9 ‘prisoners’ waiting at home "to be called" for
the start of the experiment found their homes were raided without warning by real
local police officers! They were arrested on suspicion of burglary or armed robbery,
advised of their rights, handcuffed, thoroughly searched (often in full view of their
neighbours and passers by) and driven in the back of a police car to the police station.
(The Palo Alto Police had agreed to help with the experiment!) As if they were real-
Throughout the arrest procedure, the police officers involved maintained a formal, serious attitude, and did not tell the participants that this had anything to do with the mock prison study.
The ‘prisoners’ were then blindfolded and driven by one of the experimenters and a ‘guard’ to the basement of Jordan Hall (‘Stanford County Prison’). At the mock prison, each prisoner was stripped, sprayed with a delousing preparation (a deodorant spray) and made to stand alone and naked in the ‘yard’. After being given their uniform and having a mug shot taken, the prisoner was put in his cell and ordered to remain silent.
The warden read them the rules of the institution which were to be memorised and had to be followed. Prisoners were to
be referred to only by the number on their uniforms -
Every day the participants were allowed 3 bland meals, 3 supervised toilet visits
and given 2 hours for the privilege of reading or letter writing. Work assignments
had to be carried out and 2 visiting periods per week were scheduled, as were movie
rights and exercise periods. 3 times a day prisoners were lined up for a ‘count’
(one on each guard work-
FINDINGS (RESULTS): On the second day of the experiment the prisoners organised a
mass revolt and riot, as a protest about the conditions. They taunted and cursed
the guards. Guards worked extra hours and devised a strategy to break up and put
down the riot, using fire-
Despite the fact that guards and prisoners were essentially free to engage in any form of interaction, the nature of their encounters tended to be negative, hostile, insulting and dehumanising. The guards started most of the interactions, many of which were in the form of commands or verbal affronts, while the prisoners adopted a generally passive response mode. Although it was clear to all participants that the experimenters would not permit physical violence to take place, varieties of less direct aggressive behaviour were often observed.
Lengthy prisoner counts became a trial of ordeal -
been confiscated from the prisoners, they were forced to sleep on cold, hard floors.
Initially punishments took the form of loss of privileges but the guards rapidly
increased total control of each prisoner's life, including going to the toilet. Prisoners
were often not allowed to use the toilet and forced to urinate or defecate in a bucket
in their cell -
Solitary confinement in ‘the hole’ was used. Often they also coerced prisoners to
become snitches in exchange for reduced abuse. Especially when they were bored or
thought that the experimenters were not watching, their treatment of the prisoners
would escalate and became more pornographic. The ill-
The humiliation and dehumanisation got so severe, that the experimenters had to frequently remind the guards to refrain from such tactics.
Prisoners became passive, excessively obedient, showed flattened mood and distorted perception of self, often slouching and keeping their eyes fixed to the ground,They had become institutionalised very quickly and adapted to their roles. One third of the guards began to show an extreme streak of sadism; and some of them were so enthusiastic that they volunteered to work extra hours without pay. Zimbardo himself started to become internalised
in the experiment.
The prisoners started to experience acute emotional disturbance, acute anxiety, crying and rage. They exhibited disorganised thinking, uncontrollable crying, withdrawing and behaving in pathological ways.
Overall, researchers had to release 5 prisoners from the experiment prematurely -
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 in ‘the hole’, all but one refused to give up their blanket.
Other people connected to the experiment were also sucked in by the situation. The experimenters forgot that they were there to observe and collect data. Instead, they started to assume the role of prison staff and supervisor. A priest who visited the prison started to contact parents of the prisoners about arranging lawyers to bail them out. The parents, who had visited the prison themselves, seem to also have forgot that their sons had the right to withdraw from the experiment. They actually started to arrange lawyers. And a lawyer actually came...with 5 prisoners appearing before a ‘parole board’! (One prisoner developed a rash over his entire body when his ‘parole’ was rejected!)
However, when on the fourth day, Zimbardo and the guards attempted to move the prisoners to the more secure local police station on the basis that some prisoners were talking about trying to escape, the officials at the station said they could no longer participate in the experiment.
The experiment carried on for 6 days until an outside psychologist, Christina Maslach
All of the remaining prisoners were delighted by the end of the experiment; but most
of the guards seemed to be distressed by the premature end to the study -
However there were individual differences in styles of coping with the experience. Half the prisoners endured the oppressive
atmosphere. Not all the guards resorted to hostility; some were tough but fair while some went far beyond their roles to engage in creative cruelty and harassment.
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