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Stanford Prison Experiment

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Stanford Prison Experiment

One of the most famous and controversial experiments regarding social conformity was Phillip Zimbardo’s (1971) Stanford Prison Experiment, which investigated the power of social norms and roles and the influence of authority figures. How can we apply this to an everyday example?

Imagine a teacher gets called out of the classroom and tells one student that for the remainder of the period, they’re in charge. Although the student in charge could do absolutely anything with the authority given them (e.g., get fellow students to put on music and learn a dance, have a picnic in the classroom, do some face painting or build a labyrinth out of school chairs), often the student in charge will start to give orders, shout, and generally copy the behaviour of everyone’s least favourite teacher. Why is that?

In everyday English, we’d say, ‘the power went to her head’. In psychological terms, that’s called identifying with a role. You identify with a role when you go beyond what you were told to do because you want to please others or be accepted. This is also a part of conformity, which is behaviour that complies with both spoken and unspoken rules of behaviour. Referring back to the example of the student acting as a teacher, they are conforming to a social role and the social norms or expected behaviour of a teacher.

Historically there have been many instances of people perpetrating human rights abuses when they are in a position of authority such as soldiers, guards, police officers or teachers. This is why finding out why authority figures become abusive is an important topic of research in social psychology. Thus, let us dissect Zimbardo’s Stanford prison experiment, providing its summary, description, and uncovering its ethical issues.

Stanford prison experiment summary

During the 1970s in the USA, there was a lot of public debate about the rapidly growing prison population and police brutality. This prompted Zimbardo to investigate the extent to which a person’s behaviour would change depending on the role they take on.

What were the aims of the Stanford prison experiment?

Zimbardo showed that the temporary situations that surround an individual can influence anyone to act negatively (situational influence), more so than their personality (dispositional influence). By creating a realistic environment and power dynamic between two groups, Zimbardo created pressure to conform to specific group roles.

What were the experimental conditions of the Stanford prison experiment?

There were two experimental conditions; the independent variable was the random assignment of either the ‘prisoner’ or ‘guard’ role. Zimbardo’s team gave the different groups clothing and accessories that matched their role. The ‘guards’ received uniforms, sunglasses and batons and the ‘prisoners’ wore a robe with a number and shackles. The ‘prisoners’ were confined day and night, whereas the ‘guards’ could go home.

Stanford Prison Experiment Newspaper ad recruiting for the Stanford prison experiment StudySmarterNewspaper ad recruiting for the Stanford Prison Experiment. The ad reads ‘Male college students needed for the psychological study of prison life. $15 per day for 1-2 weeks beginning Aug. 14. For further information & applications, come to Room 248, Jordan Hall, Stanford U, Wikimedia


Who were the participants in the Stanford prison experiment?

24 subjects were recruited through a local newspaper advertisement, where participants would be given a reward of $15 per day to participate in a study about ‘prison life’. They were mostly white, middle class, male university students. None of them had been in prison before and tested for any pre-existing psychological or medical conditions. After Zimbardo tested and briefed the candidates, he sent them home.

Stanford prison experiment description

During the summer break at Stanford University, Zimbardo built a mock prison in the hallways of the psychology department. After having randomly assigned the role of either prisoner or guard to the subjects, he had the ‘prisoners’ arrested by the actual local Palo Alto police without warning. They were blindfolded and brought to a real police station to have their fingerprints and picture taken, then ‘charged’ with assault and brought to the mock prison.

Here the guards made the ‘prisoners’ get undressed and put on shackles and robes, then confined them in the mock ‘cells’ that had no amenities except for a mattress. They stayed in the prison day and night, whereas ‘guards’ worked in shifts and could return home when they were not on duty.

The ‘guards’ to establish order and. They were told not to harm the ‘prisoners’ or withhold food or drink from them, however, over the course of the study, violence started to escalate:

  • Day 1: Uneventful.

  • Day 2: The prisoners barricaded themselves in a room with their mattresses. A cycle of retaliation between the two groups began. One ‘prisoner’ has a nervous breakdown.

  • Days 3-5: The ‘guards’ found increasingly extreme methods to establish control over the ‘prisoners’ by:

  1. Locking those who didn’t comply in a cupboard.

  2. Waking ‘prisoners’ up in the middle of the night for headcounts.

  3. Stripping ‘prisoners’ naked and using a fire extinguisher on them.

  4. Verbally assaulting and humiliating them.

  5. Making ‘prisoners’ defecate in a bucket and not allowing them to empty it.

  6. Withholding mattresses.

  • Day 6: The study was cut short by Zimbardo.

This experiment is considered to be an example of conformity to social roles because there was a difference between the participants’ behaviour while they were in the ‘prison’ context and outside of it. During the study, the more extreme ‘guards’ encouraged the peaceful ones to use more force. They admitted to acting in ways which they afterwards said was different from their normal behaviour outside of the study.

Subsequently, the ‘prisoners’ became more depressed and submissive over time, to the point where they reported thinking they deserved to be in prison, even though they had done nothing wrong.

What were the results of the Stanford prison experiment?

Zimbardo’s experiment is an example of normative social influence and situational influence. All of the participants started as part of the same group but when randomly assigned new social roles, started to identify and behave without explicit prompting. Zimbardo suggests that there was a degree of cognitive dissonance, meaning participants behaved in ways they didn’t want to behave, and started to identify with their roles.

Nobody died during the experiment as Zimbardo cut it short when the behaviour of the guards started to get out of hand. All participants were debriefed by Zimbardo’s team, giving them the opportunity to discuss the events of the study. Surprisingly, Zimbardo never faced legal charges despite endangering the participants under his care.


What were some criticisms of the Stanford prison experiment?

Although Zimbardo’s study was so influential that it determined policy in the USA prison system, Zimbardo’s study and his interpretation of the results has been extensively criticised.

Was the observed behaviour in the Stanford prison experiment real or roleplaying?

Researchers Banuazizi and Mohavedi (1975) claimed that the participants in the study were only playing up to stereotypes and not to actual societal roles, hence, limiting the validity of the study.

Another researcher, Peter Gray (2013) commented that the guards were encouraged to act in a psychologically oppressive manner, suggesting that in some way, Zimbardo may have produced the results through the instructions he gave the ‘guards’. This is called a demand characteristic, as participants may have subconsciously acted in the way that is expected of them.

Stanford prison experiment ethical issues

The Stanford Prison Experiment shaped ethical standards for psychological experiments because it was such a cautionary example of what not to do. Although the participants reported distress and mental trauma through the study, Zimbardo did not listen to them. His objectivity was compromised because he had taken on the role of the prison warden. This created conflict with his responsibility as the lead researcher to safeguard the physical and mental health of his subjects. When a participant asked to leave the study, Zimbardo denied his request and kept him confined against his will. Since the Stanford Prison Experiment, ethics commissions have been established in the UK and USA to pre-approve all psychological research.

What role did dispositional influence and sample bias play in the Stanford prison experiment?

Erich Fromm (1973) criticised Zimbardo’s experiment for exaggerating the results from the study; specifically, two-thirds of the guards did not act abusively, opposed to the one third who did. Additionally, Haslam and Reicher (2002) aimed to replicate the experiment in the BBC prison study. In this study, the ‘guards’ and ‘prisoners’ did not automatically conform to their roles and this led to a collapse of the prison system in the study.

The possibility of Zimbardo’s recruitment process having produced a biased sample was investigated by Carnahan (2007) in a replication study where he repeated the original recruitment process but also recruited a control group by putting out an ad for a ‘psychological study’. In the subsequent personality tests of the candidates, it was found that those candidates who had responded to the ‘prison life’ had scored higher in tests of aggression and social dominance and lower in empathy than the control group.

Stanford Prison Experiment - Key takeaways

  • Zimbardo (1971) investigated conformity to social roles in his Stanford Prison Experiment.
  • The Stanford Prison Experiment demonstrates situational influence.
  • The Stanford Prison Experiment used questionable research practices that led to stricter ethics regulations in the field of psychology.
  • Additional studies have shown that dispositional factors also determine whether or to which extent people conform to social roles.
  • Some criticisms of the Stanford Prison Experiment are that it is possible that the sample was biased and that the situation did not produce real behaviour.

Frequently Asked Questions about Stanford Prison Experiment

Nobody died in the Stanford prison experiment. Participants, however, were harmed through mistreatment and humiliation.

Zimbardo did not get into trouble for the Stanford prison experiment; neither civil nor criminal charges were filed against him and he kept his position at Stanford University.

One of the most famous and controversial experiments regarding social conformity was Phillip Zimbardo’s (1971) Stanford prison experiment, which investigated the power of social norms and roles and the influence of authority figures.

In 1971.

Zimbardo showed that the temporary situations that surround an individual can influence anyone to act negatively (situational influence), more so than their personality (dispositional influence). By creating a realistic environment and power dynamic between two groups, Zimbardo created pressure to conform to specific group roles.

The Stanford Prison Experiment shaped ethical standards for psychological experiments because it was such a cautionary example of what not to do. Although the participants reported distress and mental trauma through the study, Zimbardo did not listen to them. His objectivity was compromised because he had taken on the role of the prison warden. This created conflict with his responsibility as the lead researcher to safeguard the physical and mental health of his subjects. When a participant asked to leave the study, Zimbardo denied his request and kept him confined against his will. Since the Stanford Prison Experiment, ethics commissions have been established in the UK and USA to pre-approve all psychological research.

Zimbardo, the lead researcher of the Stanford Prison Experiment, concluded that when roles were assigned randomly to a group of similar people, these roles and the circumstances would make people behave a certain way, rather than their personality.

Zimbardo had two conflicting roles in the Stanford prison experiment - on one hand, he was the lead researcher meant to safeguard his participants, on the other hand, he played the role of the warden, keeping study subjects in the experiment even when they were being psychologically harmed.

Final Stanford Prison Experiment Quiz

Question

What was Zimbardo investigating 

in the Stanford Prison Experiment?

Show answer

Answer

Zimbardo was investigating the situational influence on conformity to social roles in the Stanford Prison Experiment.

Show question

Question

What indirect contribution did the Stanford Prison Experiment 

make to the science of psychology?



Show answer

Answer

It led to stricter ethics monitoring procedures for psychological research.

Show question

Question

How were the two experimental conditions (“guard” or “prisoner”) assigned?


Show answer

Answer

They were assigned randomly.



Show question

Question

What was the demographic of the sample of the Stanford Prison Experiment?



Show answer

Answer

The sample was made up of 24 male, mostly white, middle-class students.

Show question

Question

True or false - the study participants reported to the fake prison in the basement of Stanford University on the first day of the study.



Show answer

Answer

False - the study participants had reported to the University for a screening, but on the first day of the experiment they were arrested in their homes and brought first to the police station, then the mock jail.

Show question

Question

Were the prisoners and guards 

allowed to go home at night?



Show answer

Answer

The prisoners weren’t allowed to go 

home at night but the guards were.

Show question

Question

Were the prisoners allowed to leave when they asked Zimbardo and the guards?


Show answer

Answer

The prisoners were not allowed to leave when they asked Zimbardo or the guards. They however could have walked out or, as some did, insisted on leaving.

Show question

Question

What makes the Stanford Prison 

Experiment considered unethical?


Show answer

Answer

Even though there was no physical abuse, study participants suffered under psychological strain- one had a nervous breakdown. Also, they were verbally refused to leave the study, which means they were lied to, as they were always free to leave.



Show question

Question

What’s it called when you are doing something 

that conflicts with your own values?


Show answer

Answer

When you behave in a way that conflicts with your

own values, it’s called cognitive dissonance.

Show question

Question

What’s it called when you are doing something 

that conflicts with your own values?

Show answer

Answer

When you behave in a way that conflicts with your 

own values, it’s called cognitive dissonance.

Show question

Question

What indicated to Zimbardo that both prisoners and 

guards started to identify with their roles?

Show answer

Answer

The guards started to show unprompted authoritative behaviour and the 

prisoners started to believe that they had deserved to be in jail.

Show question

Question

What is a demand characteristic?



Show answer

Answer

A demand characteristic is when 

a study participant subconsciously 

behaves in a way that they feel is expected of them.

Show question

Question

What later research into conformity to social 

roles indicate that there might have been 

some dispositional influence at play in 

the Stanford Prison Experiment?



Show answer

Answer

Carnahan’s (2012) replication of the Stanford Prison Experiment using two different ads shows that people with higher personality test scores in aggression and lack of empathy were more drawn to the ad for a study about “prison life” than those drawn to the other ad.

Show question

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