Summary how long is it gonna take for a summary? Zimbardo, Philip. “The Stanford Prison Experiment: A Simulation Study of the Psychology of Imprisonment C
Summary how long is it gonna take for a summary? Zimbardo, Philip. “The Stanford Prison Experiment: A Simulation Study of the Psychology of Imprisonment Conducted
August 1971 at Stanford University.” Stanford. Web. 24 September 2012 http://www-sul.stanford.edu
This document is a print copy of a transcript that originally accompanied a traveling non-profit educational lecture
conceived, designed and executed by Philip Zimbardo. Original page breaks are indicated with a black line accompanied
by the original page designation. When writing about this text, use the original page numbers (1-17) to indicate
location for in-text citations.
_____________________________________________Narration page 1_______________________________________
A Quiet Sunday Morning | On a quiet Sunday morning in August, a Palo Alto, California, police car swept through the
town picking up college students as part of a mass arrest for violation of Penal Codes 211, Armed Robbery, and Burglary,
a 459 PC. The suspect was picked up at his home, charged, warned of his legal rights, spread-eagled against the police
car, searched, and handcuffed — often as surprised and curious neighbors looked on.
The suspect was then put in the rear of the police car and carried off to the police station, the sirens wailing.
The car arrived at the station, the suspect was brought inside, formally booked, again warned of his Miranda rights, finger
printed, and a complete identification was made. The suspect was then taken to a holding cell where he was left
blindfolded to ponder his fate and wonder what he had done to get himself into this mess.
Volunteers | What suspects had done was to answer a local newspaper ad calling for volunteers in a study of the
psychological effects of prison life. We wanted to see what the psychological effects were of becoming a prisoner or
prison guard. To do this, we decided to set up a simulated a prison and then carefully note the effects of this institution on
the behavior of all those within its walls. More than 70 applicants answered our ad and were given diagnostic interviews
and personality tests to eliminate candidates with psychological problems, medical disabilities, or a history of crime or
drug abuse. Ultimately, we were left with a sample of 24 college students from the U.S. and Canada who happened to be
in the Stanford area during the summer __________________________end of page 1________________________
and wanted to earn $15/day by participating in a study. On all dimensions that we were able to test or observe, they
reacted normally. Our study of prison life began, then, 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 experiment there were no differences
between boys assigned to be a prisoner and boys assigned to be a guard.
Constructing the Experiment | To help us closely simulate a prison environment, we called upon the services of
experienced consultants. Foremost among them was a former prisoner who had served nearly seventeen years behind bars.
This consultant made us aware of what it was like to be a prisoner. He also introduced us to a number of other ex-convicts
and correctional personnel during an earlier Stanford summer school class we co-taught on “The Psychology of
Imprisonment.” Our prison was constructed by boarding up each end of a corridor in the basement of Stanford’s
Psychology Department building. That corridor was “The Yard” and was the only outside place where prisoners were
allowed to walk, eat, or exercise, except to go to the toilet down the hallway (which prisoners did blindfolded so as not to
know the way out of the prison). To create prison cells, we took the doors off some laboratory rooms and replaced them
with specially made doors with steel bars and cell numbers.
At one end of the hall was a small opening through which we could videotape and record the events that occurred. On the
side of the corridor opposite the cells was a small closet which became “The Hole,” or solitary confinement. It was dark
and very confining, about two feet wide and two feet deep, but tall enough that a “bad prisoner” could stand up.
An intercom system allowed us to secretly bug the cells to monitor what the prisoners discussed, and also to make public
announcements to the prisoners. There were no windows or clocks to judge the passage of time, which later resulted in
some time-distorting experiences.
With these features in place, our jail was ready to receive its first prisoners, who were waiting in the detention cells of the
Palo Alto Police Department.
A State of Mild Shock | Blindfolded and in a state of mild shock over their surprise arrest by the city police, our
prisoners were put into a car and driven to the “Stanford County Jail” for further processing. _______end of page 2______
The prisoners were then brought into our jail one at a time and greeted by the warden, who conveyed the seriousness of
their offense and their new status as prisoners.
Humiliation | Each prisoner was systematically searched and stripped naked. He was then deloused with a spray, to
convey our belief that he may have germs or lice — as can be seen in this series of photos.
A degradation procedure was designed in part to humiliate prisoners and in part to be sure they wasn’t bringing in any
germs to contaminate our jail. This procedure was similar to the scenes captured by Danny Lyons in these Texas prison
The prisoner was then issued a uniform. The main part of this uniform was a dress, or smock, which each prisoner wore at
all times with no underclothes. On the smock, in front and in back, was his prison ID number. On each prisoner’s right
ankle was a heavy chain, bolted on and worn at all times. Rubber sandals were the footwear, and each prisoner covered
his hair with a stocking cap made from a woman’s nylon stocking.
It should be clear that we were trying to create a functional simulation of a prison — not a literal prison. Real male
prisoners don’t wear dresses, but real male prisoners do feel humiliated and do feel emasculated. Our goal was to produce
similar effects quickly by putting men in a dress without any underclothes. Indeed, as soon as some of our prisoners were
put in these uniforms they began to walk and to sit differently, and to hold themselves differently — more like a woman
than like a man.
The chain on their foot, which also is uncommon in most prisons, was used in order to remind prisoners of the
oppressiveness of their environment. Even when prisoners were asleep, they could not escape the atmosphere of
oppression. When a prisoner turned over, the chain would hit his other foot, waking him up and reminding him that he
was still in prison, unable to escape even in his dreams.
The use of ID numbers was a way to make prisoner feel anonymous. Each prisoner had to be called only by his ID
number and could only refer to himself and the other prisoners by number.
The stocking cap on his head was a substitute for having the prisoner’s hair shaved off. This ______end page 3 _________
process of having one’s head shaved, which takes place in most prisons as well as in the military, is designed in part to
minimize each person’s individuality, since some people express their individuality through hair style or length. It is also a
way of getting people to begin complying with the arbitrary, coercive rules of the institution. The dramatic change in
appearance of having one’s head shaved can be seen on this page.
Enforcing Law | The guards were given no specific training on how to be guards. Instead they were free, within limits,
to do whatever they thought was necessary to maintain law and order in the prison and to command the respect of the
prisoners. The guards made up their own set of rules, which they then carried into effect under the supervision of Warden
David Jaffe, an undergraduate from Stanford University. They were warned, however, of the potential seriousness of their
mission and of the possible dangers in the situation they were about to enter, as, of course, are real guards who voluntarily
take such a dangerous job. As with real prisoners, our prisoners expected some harassment, to have their privacy and
some of their other civil rights violated while they were in prison, and to get a minimally adequate diet — all part of their
informed consent agreement when they volunteered.
This is what one of our guards looked like. All guards were dressed in identical uniforms of khaki, and they carried a
whistle around their neck and a billy club borrowed from the police. Guards also wore special sun-glasses, an idea I
borrowed from the movie “Cool Hand Luke.” Mirror sunglasses prevented anyone from seeing their eyes or reading their
emotions, and thus helped to further promote their anonymity. We were, of course, studying not only the prisoners but
also the guards, who found themselves in a new power-laden role.
We began with nine guards and nine prisoners in our jail. Three guards worked each of three eight-hour shifts, while three
prisoners occupied each of the three barren cells around the clock. The remaining guards and prisoners from our sample of
24 were on call in case they were needed. The cells were so small that there was room for only three cots on which the
prisoners slept or sat, with room for little else. __________________end page 4 _________________________________
Asserting Authority | At 2:30 A.M. the prisoners were rudely awakened from sleep by blasting whistles for the first of
many “counts.” The counts served the purpose of familiarizing the prisoners with their numbers (counts took place several
times each shift and often at night). But more importantly, these events provided a regular occasion for the guards to
exercise control over the prisoners. At first, the prisoners were not completely into their roles and did not take the counts
too seriously. They were still trying to assert their independence. The guards, too, were feeling out their new roles and
were not yet sure how to assert authority over their prisoners. This was the beginning of a series of direct confrontations
between the guards and prisoners.
Push-ups were a common form of physical punishment imposed by the guards to punish infractions of the rules or
displays of improper attitudes toward the guards or institution. When we saw the guards demand push-ups from the
prisoners, we initially thought this was an inappropriate kind of punishment for a prison — a rather juvenile and minimal
form of punishment. However, we later learned that push-ups were often used as a form of punishment in Nazi
concentration camps, as can be seen in this drawing by a former concentration camp inmate, Alfred Kantor. It’s
noteworthy that one of our guards also stepped on the prisoners’ backs while they did push-ups, or made other prisoners sit
or step on the backs of fellow prisoners doing their push-ups.
Asserting Independence | Because the first day passed without incident, we were surprised and totally unprepared for
the rebellion which broke out on the morning of the second day. The prisoners removed their stocking caps, ripped off
their numbers, and barricaded themselves inside the cells by putting their beds against the door. And now the problem was
what were we going to do about this rebellion? The guards were very much angered and frustrated because the prisoners
also began to taunt and curse them. When the morning shift of guards came on, they became upset at the night shift who,
they felt, was too lenient. The guards had to handle the rebellion themselves and what they did was fascinating for the
staff to behold.
At first they insisted that reinforcements be called in. The three guards who were waiting on stand-by call at home came
in and the night shift of guards voluntarily remained on duty to bolster the morning shift. The guards met and decided to
treat force with force. ____________________________________end page 5 ___________________________________
They got a fire extinguisher which shot a stream of skin-chilling carbon dioxide, and they forced the prisoners away from
the doors. (The fire extinguishers were present in compliance with the requirement by the Stanford Human Subjects
Research Panel, which was concerned about potential fire threats.)
The guards broke into each cell, stripped the prisoners naked, took the beds out, forced the ringleaders of the prisoner
rebellion into solitary confinement, and generally began to harass and intimidate the prisoners.
Special Privileges | The rebellion had been temporarily crushed, but now a new problem faced the guards. Sure, nine
guards with clubs could put down a rebellion by nine prisoners, but you couldn’t have nine guards on duty at all times. It’s
obvious that our prison budget could not support such a ratio of staff to inmates. So what were they going to do? One of
the guards came up a solution. “Let’s use psychological tactics instead of physical ones.” Psychological tactics amounted
to setting up a privilege cell. One of the three cells was designated as a “privilege cell.” The three prisoners least involved
in the rebellion were given special privileges. They got their uniforms back, got their beds back, and were allowed to wash
and brush their teeth. The others were not. Privileged prisoners also got to eat special food in the presence of the other
prisoners who had temporarily lost the privilege of eating. The effect was to break the solidarity among prisoners.
After half a day of this treatment, the guards then took some of these “good” prisoners and put them into the “bad” cells,
and took some of the “bad” prisoners and put them into the “good” cell, thoroughly confusing all the prisoners. Some of
the prisoners who were the ringleaders now thought that the prisoners from the privileged cell must be informers, and
suddenly, the prisoners became distrustful of each other. Our ex-convict consultants later informed us that a similar tactic
is used by real guards in real prisons to break prisoner alliances. For example, racism is used to pit Blacks, Chicanos, and
Anglos against each other. In fact, in a real prison the greatest threat to any prisoner’s life comes from fellow prisoners. By
dividing and conquering in this way, guards promote aggression among inmates, thereby deflecting it from themselves.
__________________________________________ end page 6 ______________________________________________
The prisoners’ rebellion also played an important role in producing greater solidarity among the guards. Now, suddenly, it
was no longer just an experiment, no longer a simple simulation. Instead, the guards saw the prisoners as troublemakers
who were out to get them, who might really cause them some harm. In response to this threat, the guards began stepping
up their control, surveillance, and aggression.
Every aspect of the prisoners’ behavior fell under the total and arbitrary control of the guards. Even going to the toilet
became a privilege which a guard could grant or deny at his whim. Indeed, after the nightly 10:00 P.M. lights out “lock-
up,” prisoners were often forced to urinate or defecate in a bucket that was left in their cell. On occasion the guards would
not allow prisoners to empty these buckets, and soon the prison began to smell of urine and feces — further adding to the
degrading quality of the environment.
The guards were especially tough on the ringleader of the rebellion, Prisoner #5401. He was a heavy smoker, and they
controlled him by regulating his opportunity to smoke. We later learned, while censoring the prisoners’ mail, that he was a
self-styled radical activist. He had volunteered in order to “expose” our study, which he mistakenly thought was an
establishment tool to find ways to control student radicals. In fact, he had planned to sell the story to an underground
newspaper when the experiment was over! However, even he fell so completely into the role of prisoner that he was proud
to be elected leader of the Stanford County Jail Grievance Committee, as revealed in a letter to his girlfriend.
______________________________________________end page 7___________________________________________
The First Prisoner Released | Less than 36 hours into the experiment, Prisoner #8612 began suffering from acute
emotional disturbance, disorganized thinking, uncontrollable crying, and rage. In spite of all of this, we had already come
to think so much like prison authorities that we thought he was trying to “con” us — to fool us into releasing him.
When our primary prison consultant interviewed Prisoner #8612, the consultant chided him for being so weak, and told
him what kind of abuse he could expect from the guards and the prisoners if he were in San Quentin Prison. #8612 was
then given the offer of becoming an informant in exchange for no further guard harassment. He was told to think it over.
During the next count, Prisoner #8612 told other prisoners, “You can’t leave. You can’t quit.” That sent a chilling message
and heightened their sense of really being imprisoned. #8612 then began to act “crazy,” to scream, to curse, to go into a
rage that seemed out of control. It took quite a while before we became convinced that he was really suffering and that we
had to release him.
Parents and Friends | The next day, we held a visiting hour for parents and friends. We were worried that when the
parents saw the state of our jail, they might insist on taking their sons home. To counter this, we manipulated both the
situation and the visitors by making the prison environment seem pleasant and benign. We washed, shaved, and groomed
the prisoners, had them clean and polish their cells, fed them a big dinner, played music on the intercom, and even had an
attractive former Stanford cheerleader, Susie Phillips, greet the visitors at our registration desk. When the dozen or so
visitors came, full of good humor at what seemed to be a novel, fun experience, we systematically brought their behavior
under situational control. They had to register, were made to wait half an hour, were told that only two visitors could see
any one prisoner, were limited to only ten minutes of visiting time, and had to be under the surveillance of a guard during
the visit. Before any parents could enter the visiting area, they also had to discuss their son’s case with the Warden. Of
course, parents complained about these arbitrary rules, but remarkably, they complied with them. And so they, too,
became bit players in our prison drama, being good middle-class adults. _______________end page 8 _______________
Some of the parents got upset when they saw how fatigued and distressed their son was. But their reaction was to work
within the system to appeal privately to the Superintendent to make conditions better for their boy. When one mother told
me she had never seen her son looking so bad, I responded by shifting the blame from the situation to her son. “What’s the
matter with your boy? Doesn’t he sleep well?” Then I asked the father, “Don’t you think your boy can handle this?”
He bristled, “Of course he can — he’s a real tough kid, a leader.” Turning to the mother, he said, “Come on Honey, we’ve
wasted enough time already.” And to me, “See you again at the next visiting time.”
A Mass Escape Plot | The next major event we had to contend with was a rumored mass escape plot. One of the guards
overheard the prisoners talking about an escape that would take place immediately after visiting hours. The rumor went as
follows: Prisoner #8612, whom we had released the night before, was going to round up a bunch of his friends and break
in to free the prisoners. How do you think we reacted to this rumor? Do you think we recorded the pattern of rumor
transmission and prepared to observe the impending escape? That was what we should have done, of course, if we were
acting like experimental social psychologists. Instead, we reacted with concern over the security of our prison. What we
did was to hold a strategy session with the Warden, the Superintendent, and one of the chief lieutenants, Craig Haney, to
plan how to foil the escape.
After our meeting, we decided to put an informant (an experimental confederate) in the cell that #8612 had occupied. The
job of our informant would be to give us information about the escape plot. Then I went back to the Palo Alto Police
Department and asked the sergeant if we could have our prisoners transferred to their old jail. My request was turned
down because the Police Department would not be covered by insurance if we moved our prisoners into their jail. I left
angry and disgusted at this lack of cooperation between our correctional facilities (I was now totally into my role).
Then we formulated a second plan. The plan was to dismantle our jail after the visitors left, call in more guards, chain the
prisoners together, put bags over their heads, and transport them to a fifth floor storage room until after the anticipated
break in. _________________________________________end page 9_____________________________________
When the conspirators came, I would be sitting there alone. I would tell them that the experiment was over and we had
sent all of their friends home, that there was nothing left to liberate. After they left, we’d bring our prisoners back and
redouble the security of our prison. We even thought of luring #8612 back on some pretext and then imprisoning him
again because he was released on false pretenses.
A Visit | I was sitting there all alone, waiting anxiously for the intruders to break in, when who should happen along but
a colleague and former Yale graduate student roommate, Gordon Bower. Gordon had heard we were doing an experiment,
and he came to see what was going on. I briefly described what we were up to, and Gordon asked me a very simple
question: “Say, what’s the independent variable in this study?” To my surprise, I got really angry at him. Here I had a
prison break on my hands. The security of my men and the stability of my prison was at stake, and now, I had to deal with
this bleeding-heart, liberal, academic, effete dingdong who was concerned about the independent variable! It wasn’t until
much later that I realized how far into my prison role I was at that point — that I was thinking like a prison superintendent
rather than a research psychologist.
Paying Them Back | The rumor of the prison break turned out to be just a rumor. It never materialized. Imagine our
reaction! We had spent an entire day planning to foil the escape, we begged the police department for help, moved our
prisoners, dismantled most of the prison — we didn’t even collect any data that day. How did we react to this mess? With
considerable frustration and feelings of dissonance over the effort we had put in to no avail. Someone was going to pay.
____________________________________________end of page 10________________________________________
The guards again escalated very noticeably their level of harassment, increasing the humiliation they made the prisoners
suffer, forcing them to do menial, repetitive work such as cleaning out toilet bowls with their bare hands. The guards had
prisoners do push-ups, jumping jacks, whatever the guards could think up, and they increased the length of the counts to
several hours each.
A Kafkaesque Element | At this point in the study, I invited a Catholic priest who had been a prison chaplain to
evaluate how realistic our prison situation was, and the result was truly Kafkaesque. The chaplain interviewed each
prisoner individually, and I watched in amazement as half the prisoners introduced themselves by number rather than
name. After some small talk, he popped the key question: “Son, what are you doing to get out of here?” When the
prisoners responded with puzzlement, he explained that the only way to get out of prison was with the help of a lawyer.
He then volunteered to contact their parents to get legal aid if they wanted him to, and some of the prisoners accepted his
offer. The priest’s visit further blurred the line between role-playing and reality. In daily life this man was a real priest, but
he had learned to play a stereotyped, programmed role so well — talking in a certain way, folding his hands in a prescribed
manner — that he seemed more like a movie version of a priest than a real priest, thereby adding to the uncertainty we
were all feeling about where our roles ended and our personal identities began. _____________end page 11___________
#819 | The only prisoner who did not want to speak to the priest was Prisoner #819, who was feeling sick, had refused
to eat, and wanted to see a doctor rather than a priest. Eventually he was persuaded to come out of his cell and talk to the
priest and superintendent so we could see what kind of a doctor he needed. While talking to us, he broke down and began
to cry hysterically, just as had the other two boys we released earlier. I took the chain off his foot, the cap off his head, and
told him to go and rest in a room that was adjacent to the prison yard. I said that I would get him some food and then take
him to see a doctor. While I was doing this, one of the guards lined up the other prisoners and had them chant aloud:
“Prisoner #819 is a bad prisoner. Because of what Prisoner #819 did, my cell is a mess, Mr. Correctional Officer.” They
shouted this statement in unison a dozen times.
As soon as I realized that #819 could hear the chanting, I raced back to the room where I had left him, and what I found
was a boy sobbing uncontrollably while in the background his fellow prisoners were yelling that he was a bad prisoner.
No longer was the chanting disorganized and full of fun, as it had been on the first day. Now it was marked by utter
conformity and compliance, as if a single voice was saying, “#819 is bad.”
I suggested we leave, but he refused. Through his tears, he said he could not leave because the others had labeled him a
bad prisoner. Even though he was feeling sick, he wanted to go back and prove he was not a bad prisoner.
At that point I said, “Listen, you are not #819. You are [his name], and my name is Dr. Zimbardo. I am a psychologist, not
a prison superintendent, and this is not a real prison. This is just an experiment, and those are students, not prisoners, just
like you. Let’s go.” He stopped crying suddenly, looked up at me like a small child awakened from a nightmare, and
replied, “Okay, let’s go.” __________________________________end of page 12________________________________
Parole Board | The next day, all prisoners who thought they had grounds for being paroled were chained together and
individually brought before the Parole Board. The Board was composed mainly of people who were strangers to the
prisoners (departmental secretaries and graduate students) and was headed by our top prison consultant. Several
remarkable things occurred during these parole hearings. First, when we asked prisoners whether they would forfeit the
money they had earned up to that time if we were to parole them, most said yes. Then, when we ended the hearings by
telling prisoners to go back to their cells while we considered their requests, every prisoner obeyed, even though they
could have obtained the same result by simply quitting the experiment. Why did they obey? Because they felt powerless
to resist. Their sense of reality had shifted, and they no longer perceived their imprisonment as an experiment. In the
psychological prison we had created, only the correctional staff had the power to grant paroles. During the parole hearings
we also witnessed an unexpected metamorphosis of our prison consultant as he adopted the role of head of the Parole
Board. He literally became the most hated authoritarian official imaginable, so much so that when it was over he felt sick
at who he had become — his own tormentor who had previously rejected his annual parole requests for 16 years when he
was a prisoner. ___________________________________end of page 13______________________________________
Types of Guards | By the fifth day, a new relationship had emerged between prisoners and guards. The guards now fell
into their job more easily — a job which at times was boring and at times was interesting. There were three types of
guards. First, there were tough but fair guards who followed prison rules. Second, there were “good guys” who did little
favors for the prisoners and never punished them. And finally, about a third of the guards were hostile, arbitrary, and
inventive in their forms of prisoner humiliation. These guards appeared to thoroughly enjoy the power they wielded, yet
none of …