The Stanford Prison
• The Stanford prison experiment was a
study of the psychological effect of
becoming a prisoner or prison guard.
• Lasting for only six days, from August
14 to 20, 1971, the experiment was
conducted by a team of researchers at
Stanford University led by the
psychology professor Phillip Zimbardo.
• In the experiment, Zimbardo and his team
wanted to test the idea that abusive
prison situations were caused by the
inherent personality traits of prisoners
• Zimbardo’s team placed an ad in the local
newspaper calling for volunteers in a two-
week prison simulation.
• Out of the 75 respondents, most of whom
were white and middle-class, Zimbardo
and his team chose the 24 males whom
they deemed to be the most
psychologically stable and healthy to
participate in the study.
• The participants were randomly divided
into two groups by a coin flip, half of them
assigned the roles of guards, the other
half prison inmates.
• The day before the experiment, the researchers
held an orientation session for guards.
• During this session, the guards were told that
they were not permitted to physically harm the
prisoners, but they could use various
psychological methods to degrade and
dehumanize the prisoners in order to instill a
feeling of powerlessness.
• On the first day of the experiment, participants
assigned the role of prisoners were arrested at
their homes by the local police department,
which had agreed to assist Zimbardo, and
charged with armed robbery.
• Afterwards, the prisoners were transported to a
mock prison in the basement of one of the
buildings at Stanford University, where they
were to be given their new identities.
The Beginning (cont’d)
• Upon arrival, the prisoners were each greeted
individually by the warden, who recounted to
them the seriousness of their crimes.
• Each prisoner was then strip-searched and
deloused, providing a humiliating experience.
• Prisoners were forced to wear uncomfortable
clothing and assigned numbers, sewn to their
uniforms, by which guards addressed them,
rather than calling them by name. A chain
around their ankle further reinforced the role
• Guards were provided with wooden batons,
meant to establish their status, which were
not to be used on prisoners.
• The Guards were also outfitted in khaki pants
and shirts from a military surplus store, and
provided with mirrored sunglasses in order to
prevent eye contact with prisoners.
• The experiment began with nine guards and nine
prisoners in the jail.
• Three guards worked three eight hour shifts
each, while each of the three cells constantly
contained three prisoners.
• Prisoners were awakened from sleep at 2:30 AM
for “counts”, serving to familiarize the prisoners
with their numbers.
• Early on, the prisoners were still trying to assert
their independence and the guards were
inexperienced, leading to some confrontations
between prisoners and guards.
• Guards began using push-ups as a form of
physical punishment, and one of the guards
would step on the prisoners’ backs, or make
other prisoners sit or step on the backs of their
inmates doing push-ups.
• Though the first day of the experiment passed without incident,
on the morning of the second day, a rebellion broke out.
• Prisoners removed their stocking caps, ripped off their numbers,
and used their beds to barricade themselves inside their cells.
• The guards were frustrated and angry with the prisoners,
especially once the inmates began to taunt and curse them, and
even angry with each other; once the morning guards came in,
they were angry with the night guards, who they felt must have
been too lenient.
• In order to handle the rebellion, the guards first called in
reinforcements, bringing in the three guards who were waiting at
home on stand-by call.
• The guards then used a fire extinguisher to force the prisoners
away from the doors with bursts of ice-cold CO2.
• Once reinforcements arrived, the guards broke into each cell,
stripping the prisoners and removing their beds.
• After the rebellion, the guards began to harass and intimidate
Controlling the Prisoners
• After the rebellion was put down, the
guards had to find a way to keep the
prisoners under control.
• Faced with the problem of an insufficient
staff-to-prisoner ratio, one of the guards
came up with the solution of using
psychological tactics rather than physical
ones to control the prisoners.
• One of the three cells was designates as a
“privilege cell”, where the three prisoners
least involved in the rebellion were given
• This was attempted in order to break the
solidarity among prisoners.
Controlling the Prisoners (cont’d)
• The guards then took some of these
privileged prisoners and put them into
“bad” cells, replacing them with some of
the “bad” prisoners after half a day.
• Some of the ringleaders now thought
that the prisoners from the privileged cell
must be informers for the guards, and
distrust began to grow between the
• The rebellion also bolstered solidarity
among the guards.
• Instead of seeing the experiment as only
a simulation, guards began to see the
prisoners as troublemakers who were out
to get them, and began increasing their
control, surveillance and aggression
Descending Into Tyranny
• The guards began to control every single aspect of the prisoners’ lives, even the ability to be
able to go to the toilet.
• Occasionally, guards would not allow prisoners to empty their waste buckets, adding to the
degrading atmosphere of the prison.
• The guards were especially tough on Prisoner #5401, who had orchestrated the rebellion.
• Prisoner #5401 was a heavy smoker, and the guards would control him by regulating his
ability to smoke.
• Some of the guard became increasingly cruel as the experiment continued, with
experimenters saying that one-third of the guards exhibited genuine sadistic tendencies.
• When a visiting hour was held for parents and friends, the experimenters manipulated both
the situation and the visitors by making the prison environment seem pleasant.
• The experimenters had the prisoners washed, shaved, and groomed, had them clean their
cells, fed them, and played music on the intercom.
• When the visitors came, the experimenters had them register, wait half an hour, and told
them that only two visitors could see any one prisoner, could only have ten minutes of
visiting time, and had to be under guard supervision during the visit.
• The parents complained about these rules, but, surprisingly, obeyed them even so.
The First Prisoner Released
• Less than 36 hours into the experiment, one of the prisoners,
Prisoner #8612, began to break down.
• Despite this, the administrative group had fallen into their roles
as prison authorities to the point where they thought he was
trying to fool them into releasing him.
• When the primary prison consultant interviewed the prisoner,
he chided him for being so weak and then gave the prisoner the
offer of becoming an informant in exchange for escape from
• During the next count, Prisoner #8612 began to tell other
prisoners that “You can’t leave. You can’t quit”, and then began
to break down even further, to the point where the
administrative group became convinced that he really was
suffering and had to release him.
The Escape Plot
• Afterwards, one of the guards heard prisoners talking about an
escape that was planned for after visiting hours.
• The rumor stated that Prisoner #8612 was going to round up
some friends to break in and free the prisoners.
• Rather than recording the rumor transmission and preparing to
observe the escape, the experimenters reacted with concern
over the security of the prison, holding a strategy session to
plan how to stop the escape.
• After the meeting, the experimenters decided to put an
informant in the cell that Prisoner #8612 had occupied, in order
to relay information about the escape plot to the administrative
• Dr. Zimbardo then went to the Palo Alto Police Department and
asked the sergeant if the prisoners could be transferred to their
old jail, but when he was turned down he left angry and
disgusted at the lack of cooperation.
The Escape Plot (cont’d)
• A second plan was formulated; the jail was to be dismantled after
visiting hours, more guards were to be called in, and the prisoners
were to be chained together with bags placed over their heads and
then transported to a storage room until after the break in.
• When the people #8612 had gathered came, Dr. Zimbardo would
be sitting in the prison alone and would tell them that the
experiment was over and their friends had been sent home.
• After the conspirators left, the experimenters would bring the
prisoners back and increase the security of the prison.
• In the end, the rumor of the prison break turned out to be just a
• Frustrated with the amount of wasted effort they had put into
stopping the prison break, the guards noticeably increased their
level of harassment, further humiliating the prisoners and forcing
them to do menial, repetitive work such as cleaning out toilet
bowls with their bare hands.
• At this point in the study, a Catholic priest who had been a prison
chaplain was invited to come and evaluate how realistic the
prison situation was.
• The priest interviewed each prisoner individually, and half of the
prisoners introduced themselves by number instead of by name.
• One of the prisoners, Prisoner #819, was feeling sick, had refused
to eat, and wanted to see a doctor, not a priest.
• When he was convinced to come out of his cell and talk to the
priest and superintendent he broke down and began crying
• Dr. Zimbardo took the chain off his foot, the cap off his head, and
told him to go rest and that he would get him some food and
then take him to a doctor.
• While this was happening, one of the guards lined up the
remaining prisoners and had them chant: “Prisoner #819 is a bad
prisoner. Because of what Prisoner #819 did, my cell is a mess,
Mr. Correctional Officer."
• When Dr. Zimbardo heard the chanting, he went back
to the room where he had left Prisoner #819 and
suggested that they leave, but the prisoner refused.
• He didn’t want to leave because the others had
labeled him a bad prisoner, and even though he was
sick, he wanted to go back and prove he was not a bad
• Dr. Zimbardo had to remind him that this was just an
experiment before he would agree to leave and get
The Guards Transform
• By the fifth day, the guards fell into their jobs more
easily, with three types of guards arising.
• There were the tough, but fair guards who followed
prison rules, there were “good guys”, who did little
favours for the prisoners and never punished them,
and there where the hostile, arbitrary guards who
were quite inventive in their forms of prisoner
• These hostile guards, roughly a third of the group,
appeared to enjoy the power they wielded, though
none of the preliminary personality tests had
predicted this type of behavior.
• The prisoners nicknamed the most macho and brutal
guard in the study “John Wayne” because of his “Wild
West” cowboy macho image in abusing the inmates.
Prisoners’ Coping styles
• The prisoners coped with their feeling of powerlessness and
frustration in different ways.
• At first, some prisoners rebelled or fought with the guards,
and four prisoners reacted by breaking down emotionally.
• One prisoner developed a psychosomatic rash over his entire
body when he learned that his parole request had been
• Some of the prisoners tried to cope by being good prisoners,
doing whatever the guards wanted them to do.
• By the end of the study the prisoners had fallen apart, both as
individuals and as a group, with all the group unity that had
been present in the beginning disintegrating as the guards
gained total control of the prison.
• When Prisoner #416 was admitted as one of the stand-by prisoners, unlike the other
prisoners there was no gradual increasing of harassment, and he was thrown right into
the worst of the study.
• Prisoner #416 coped by going on a hunger strike in an attempt to force his release.
• After the guards were unsuccessful in getting #416 to eat, they threw him into solitary
confinement for 3 hours, even though rules stated that one hour was the limit.
• Though he should have been seen as a hero to the other prisoners, his inmates only saw
him as a troublemaker.
• The head guard then gave the prisoners a choice; they could let #416 come out of solitary
if they gave up their blankets, or they could leave him in solitary all night.
• Most prisoners chose to keep their blankets, and the administrative team was forced to
intervene and return #416 to his cell.
The End of the Experiment
• This was the point when it became clear that the study had to
• An extremely powerful situation in which prisoners were
withdrawing and guards were behaving sadistically had been
created, and even the “good” guards felt helpless to intervene.
• Dr. Zimbardo ended the study prematurely for two reasons.
• First, the administrators had learned that the guards were
further abusing the prisoners in the middle of the night when
they thought no researchers were watching.
• Secondly, Christina Maslach, objected to the horrible conditions
of the prison.
• Out of around 50 outsiders, she was the only one who ever
questioned its morality.
• The experiment ended August 20, 1971, six days after it began.
• The results of the experiment have been argued to support the idea that an individual’s
behaviour can be caused by a situation, rather than the individual’s personality.
• The experiment showed just how impressionable and obedient people can be when provided
with a dehumanizing ideology and institutional support.
• The experiment was heavily criticized as being unscientific and unethical.
• Current ethical standards of psychology would make it impossible to conduct such a study in
• Because the study was a field experiment, it was impossible to keep scientific controls in
place, and conclusions and observations by the experimenters were very subjective.
• Some critics argued that participants modeled their behaviour after stereotypes, or that
Zimbardo biased the guards when in his briefing he gave them clear instructions that they
should oppress the prisoners.