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Zimbardo - Stanford Prison Experiment

by Saul McLeo d

Aim: To investigate how readily people would conf orm to the roles of guard and prisoner in a role-playing
exercise that simulated prison lif e.

Z imbardo (1973) was interested in f inding out whether the brutality reported among guards in American prisons
was due to the sadistic personalities of the guards or had more to do with the prison environment.

Procedure: Z imbardo used a lab experiment to study conf ormity.

To study the roles people play in prison situations, Z imbardo converted a

basement of the Stanf ord University psychology building into a mock prison.
He advertised f or students to play the roles of prisoners and guards f or a
f ortnight. 21 male college students (chosen f rom 75 volunteers) were
screened f or psychological normality and paid $15 per day to take part in the
experiment.

Participants were randomly assigned to either the role of prisoner or guard in

a simulated prison environment. T he prison simulation was kept as “real lif e”
as possible. Prisoners were arrested at their own homes, without warning,
and taken to the local police station.

Guards were also issued a khaki unif orm, together with whistles, handcuf f s and
dark glasses, to make eye contact with prisoners impossible. No physical violence
was permitted. Z imbardo observed the behavior of the prisoners and guards.

Here they were treated like every other criminal. T hey were f ingerprinted,
photographed and ‘booked’. T hen they were blindf olded and driven to the
psychology department of Stanf ord University, where Z imbardo had had the
basement set out as a prison, with barred doors and windows, bare walls and small
cells. Here the deindividuation process began.

When the prisoners arrived at the prison they were stripped naked, deloused,
had all their personal possessions removed and locked away, and were given
prison clothes and bedding. T hey were issued a unif orm, and ref erred to by
their number only. T heir clothes comprised a smock with their number written
on it, but no underclothes. T hey also had a tight nylon cap, and a chain
around one ankle.

T here were 3 guards to the 9 prisoners, taking shif ts of eight hours each (the
other guards remained on call)

Findings: Within a very short time both guards and prisoners were settling
into their new roles, the guards adopting theirs quickly and easily.

Within hours of beginning the experiment some guards began to harass prisoners. T hey behaved in a brutal
and sadistic manner, apparently enjoying it. Other guards joined in, and other prisoners were also tormented.
 T he prisoners were taunted with insults and petty orders, they were given pointless and boring tasks to
accomplish, and they were generally dehumanized.

T he prisoners soon adopted prisoner-like behavior too. T hey talked about prison issues a great deal of the
time. T hey ‘told tales’ on each other to the guards. T hey started taking the prison rules very seriously, as
though they were there f or the prisoners’ benef it and inf ringement would spell disaster f or all of them. Some
even began siding with the guards against prisoners who did not conf orm to the rules.

Over the next f ew days the relationships between the guards and the prisoners changed, with a change in one
leading to a change in the other. Remember that the guards were f irmly in control and the prisoners were
totally dependent on them.

As the prisoners became more dependent, the guards became more derisive towards them. T hey held the
prisoners in contempt and let the prisoners know it. As the guards’ contempt f or them grew, the prisoners
became more submissive.

As the prisoners became more submissive, the guards became more aggressive and assertive. T hey demanded
ever greater obedience f rom the prisoners. T he prisoners were dependent on the guards f or everything so
tried to f ind ways to please the guards, such as telling tales on f ellow prisoners.

One prisoner had to be released after 36 hours because of uncontrollable bursts of screaming, crying
and anger. His thinking became disorganized and he appeared to be entering the early stages of a deep
depression. Within the next f ew days three others also had to leave af ter showing signs of emotional disorder
that could have had lasting consequences. (T hese were people who had been pronounced stable and normal a
short while bef ore.)

Z imbardo (1973) had intended that the experiment should run for a fortnight, but on the sixth day he
closed it down. T here was real danger that someone might be physically or mentally damaged if it was allowed
to run on. Af ter some time f or the researchers to gather their data the subjects were called back f or a f ollow-
up, debrief ing session.

Conclusion: People will readily conf orm to the social roles they are expected to play, especially if the roles are
as strongly stereotyped as those of the prison guards. T he “prison” environment was an important f actor in
creating the guards’ brutal behavior (none of the participants who acted as guards showed sadistic tendencies
bef ore the study). T heref ore, the roles that people play can shape their behavior and attitudes.

Af ter the prison experiment was terminated Z imbardo interviewed the participants. Here’s an excerpt:

‘Most of the participants said they had f elt involved and committed. T he research had f elt "real" to them. One
guard said, "I was surprised at myself . I made them call each other names and clean the toilets out with their
bare hands. I practically considered the prisoners cattle and I kept thinking I had to watch out f or them in case
they tried something." Another guard said "Acting authoritatively can be f un. Power can be a great pleasure."
And another: "... during the inspection I went to Cell Two to mess up a bed which a prisoner had just made and
he grabbed me, screaming that he had just made it and that he was not going to let me mess it up. He grabbed
me by the throat and although he was laughing I was pretty scared. I lashed out with my stick and hit him on the
chin although not very hard, and when I f reed myself I became angry."’

Most of the guards f ound it dif f icult to believe that they had behaved in the brutalizing ways that they had.
Many said they hadn’t known this side of them existed or that they were capable of such things. T he prisoners,
too, couldn’t believe that they had responded in the submissive, cowering, dependent way they had. Several
claimed to be assertive types normally. When asked about the guards, they described the usual three
stereotypes that can be f ound in any prison: some guards were good, some were tough but f air, and some
were cruel.
Ethics: T he study has received many ethical criticisms, including lack of f ully inf ormed consent by
participants and the level of humiliation and distress experienced by those who acted as prisoners.

T he consent could not be f ully inf ormed as Z imbardo himself did not know what would happen in the
experiment (it was unpredictable). Also, participants playing the role of prisoners were not protected from
psychological and physical harm. For example, one prisoner had to be released af ter 36 hours because of
uncontrollable bursts of screaming, crying and anger.

Ref erences

Haney, C., Banks, W. C., & Z imbardo, P. G. (1973) A study of prisoners and guards in a simulated prison. Naval
Research Review, 30, 4-17.

Furt her Inf ormat ion

Z imbardo

Z imbardo Prison Experiment

Stanf ord Prison Simulation

T he Stanf ord Prison Experiment

How t o cit e t his art icle:

McLeod, S. A. (2008). Z imbardo - Stanf ord Prison Experiment. Retrieved f rom

http://www.simplypsychology.org/zimbardo.html

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