Haney, Craig., Banks, Curtis., & Zimbardo, Philip. (1973)


The purpose of this study was to test the dispositional hypothesis. This hypothesis says that the bad environments in prisons are due to
the nature of the guards and the prisoners, NOT because of the social roles prisoners and prison guards have and conform to/the environments which they are in. This study was funded by the United States Navy as the U.S. Navy and U.S. Marine Corps were interested in the causes of conflict between the prison guards and prisoners in naval prisons. Zimbardo felt that the reason prison environments are bad not because of the nature of the people themselves, but because of the situations, environments they are put into. If this dispositional hypothesis is true than their could not be much reform in prisons, as they could not change the nature of the prisoners/prison guards. If this dispositional hypothesis was not true though, then the environments of these prisons could be improved, hopefully improving the situations in the these prisons.


The first aim of this study was to see how normal people, when taking on specific social roles, excessively conform to those roles. The second aim of this study was to test the dispositional hypothesis (the conditions of prisons are due to the nature/character of the prison guards and the prisoners).


The participants consisted of twenty-four men that were considered physically and mentally stable, mature, and the least involved in antisocial behavior. They were all college students, white, middle class, male, healthy.


The research method used in this study was an experiment.


The data collected from this study was qualitative and quantitative. It was mostly qualitative, and was collected through video, audiotape, direct observation, interviews, and questionnaires.


Qualitative data was collected.


Participants were randomly assigned to be a prisoner or a guard. As the researchers wanted to make this experiment as real as possible, police cars arrived at the participants’ houses and arrested them. They were then fingerprinted and blindfolded, searched, stripped naked, and
deloused, as any real prisoner would have to do. The prisoners were given their uniforms, which consisted of a smock with a number printed on it, a cap, and a chain around their ankle. Guards were given a uniform which consisted of khaki shirts and pants, reflective sunglasses, and batons. Prisoners stayed in the prison and followed a strict schedule which consisted of work assignments, rest, and toilet and food breaks. The guards worked in eight hour shifts.


The prison used for the experiment was located in the basement of the psychology building at Stanford University consisting of:
  • Three cells (6x9): 3 prisoners to a cell with 3 Cots (with mattress, sheet, pillow)
  • Solitary Confinement (“The Hole”): Very small, unlit room (2x2x7) across from the cells
  • Guards Quarters: Rooms in an adjacent wing for changing, relaxation, interviews, and a bedroom for the ‘warden’ (Zimbardo)
Uniforms: used to help with role identification
Guards’ uniforms: Khaki shirts and pants, batons, and reflective sunglasses
Prisoners’ uniforms: loose fitting smocks (dresses) with ID numbers, no underwear, a lock and chain around one ankle, and stocking caps to cover their hair


The experiment ended rather quickly. It ended after just 6 days instead of the planned 14 says because of the pathological reaction of participants. 5 prisoners had to be released early due to extreme emotional depression.
The guards ended up humiliating and punishing the prisoners which led the prisoners to show signs of mental and emotional distress.
On the second day the prisoners organized a revolt and riot due to the living conditions and the guards worked extra hours and developed a plan to stop the riot using, fire extinguishers. After the second day the prisoners began to feel helpless and no longer in control of their lives.
Eventually the guards became more aggressive and abusive. Many seemed to really enjoy the power and control that came along with the uniform. Some even volunteered to work extra shifts. The even continued to behave so aggressively even when they thought the cameras were not on.
The prisoners’ rights were became privileges and they were punished with little or no justification.The prisoners became institutionalized very quickly and adapted to their roles.
There was evidence of Pathological Prisoner Disorder, which includes the loss of personal identity (the prisoners ID numbers), the arbitrary control exercised by the guards, dependency and emasculation.
One prisoner left and a replacement prisoner was introduced. He went on a hunger strike in protest about the treatment of inmates and as an attempt to be released. The other inmates saw him as a troublemaker instead of a victim trying to help.


The study rejects the dispositional hypothesis.
The prison environment was an important factor in creating the guards’ brutal behavior which none of them showed before the study.
People will readily conform to the social roles they are expected to play, especially if the roles are strongly stereotyped as the guards were.
The roles that people play shape their attitudes and behavior.
If it only took six days to change the behavior of the participants in the study, imagine the greater effects in real life.


The strengths of this study are that the researchers had high levels of control and the experiment itself had high ecological validity. The way the prison was set up was very realistic, so the participants felt as if they were in a real prison.


One weakness of this study is that the participants were being paid to be in the study, so their is a possibility they were purposefully
acting a certain way to try and help the experimenters. Another weakness of this study is that many considered it to be very unethical, as the subjects faced extreme emotional distress and some were not allowed to leave right away as they had requested.


  • The study was able to maintain some degree of control.
    • The guards and prisoners were randomly allocation and were selected using a stringent criterion.
  • Zimbardo went to extremes in making the study as true to life as possible
    • Zimbardo had the participants ‘arrested’ at their houses
    • He brought in real prisoners to have them explain how the prison should be set up to make it feel real


  • The study was approved by the Office of Naval Research
  • The only deception was the arrests
  • They signed consent forms
  • Extensive group and individual debriefings were held
  • Zimbardo listened to the advice of other psychologists
  • Zimbardo stopped early
  • The information gained was worth it
  • There may have been researcher bias since Zimbardo played the warden