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Key Study: the Stanford
Prison Experiment

Part 2



CONCLUSIONS: An extremely high level of conformity was observed of ‘guards’ and ‘prisoners’ to their roles.

However, many participants reported afterwards that they had acted ‘out of character’ and had not really changed the way they thought about things (private opinion).

Personality tests indicated no significant differences between the guards’ and prisoners’ personalities which supports a situationalist rather than dispositionalist explanation of conformity resulting in extreme and/or callous behaviour towards others. Zimbardo believed that the study demonstrated the powerful effect social roles can have on peoples’ behaviour. Basically the participants were playing the role that they thought was expected of either a prisoner or prison guard. (Effectively a simulation of what prison life was thought to be, rather than what it was, as none of the participants had previously been in prison as a guard or prisoner).

In his analysis, Zimbardo categorised approximately 30% of the guards as ‘cruel and tough’; about 50% were ‘tough but fair’; and less than 20% were ‘good guards’ (generally helpful and kind to the prisoners). He explained that the reason for the deterioration in guard behaviour was power. The guards were given control over the lives of other human beings and did not have to justify their displays of

Kim Duke’s documentary of the Stanford Prison Experiment Experiment - copyright © 2002 BBC

power as they would normally have to in their daily lives. They started to enjoy this power very earlier on in the study (‘pathology of power’) as demonstrated that, even after the first day, all prisoner rights became redefined as privileges and all privileges were cancelled.

Zimbardo explained the social deterioration of the prisoners as the ‘pathological prisoner syndrome’. At the beginning of the study, the prisoners rebelled against their conditions, but the guards undermined every attempt at rebellion and any solidarity between the prisoners collapsed. Half of the prisoners responded by becoming ‘sick’ and eventually had to be released before the study was finally brought to a conclusion. The remaining prisoners became passive, dependent and had flattened emotions. Zimbardo suggested that there were a number of processes that contributed to the pathological prisoner syndrome:-

because they were smaller than the guards - in fact there was no difference in average height between the prisoners and guards; and the perceived difference appeared to be a response to the prisoners’ perception of themselves and their lack of power.


CRITICISMS (EVALUATION): Most criticisms of Zimbardo’s study are on ethical issues:-

In Zimbardo’s defence, it needs to be said that:-

There were also a number of validity issues to do with the study:-

A main strength of the study was the way it managed to maintain some degree of control and some ecological validity. The situation was very tightly controlled - eg: guards and prisoners were randomly allocated and were selected using a stringent criterion. The study still had ecological validity in the way that Zimbardo went to great extremes in making the study as true to life as possible -eg: in the way that he had the prisoners arrested from their homes.

A further strength was in the way that Zimbardo collected data.  

It is also worth noting that Zimbardo’s conclusions can be seen as too deterministic. Eg: in his study not all of the participants behaved in the same way. Some of the guards were less willing to abuse their power. Perhaps the reason why some of the participants were less willing was something to do with their personalities - ie: there could be a dispositional element in their behaviour!

Guard ‘B’ said in debrief: “I made sure I was one of the guards on the yard [when the prisoners were first admitted] because this was my first chance for the kind of manipulative power that I really like - being a very noticed figure with complete control over what is said or not.” Guard C said: “Acting authoritatively can be fun. Power can be a great pleasure.”

Alex Haslam & Steve Reicher, conducted the ‘BBC Prison Study’ in 2002, a partial replication of Zimbardo’s experiment with the assistance of the BBC. Their results and conclusions differed from Zimbardo's in that the prisoners largely came to dominate the guards. While their procedure was not a direct replication of Zimbardo's, their study cast further doubt on the generality of his conclusions. Specifically, it questions the notion that people slip mindlessly into role.

For all the outrage the Stanford Prison Experiment led to, Zimbardo’s testimony influenced Congress to change one law so that juveniles accused of federal crimes would no longer be housed with adult prisoners before trial (to prevent them from being abused).

In 2004, Zimbardo testified for the defence in the court martial of Sgt Ivan ‘Chip’ Frederick, a guard at Abu Ghraib prison. He argued that Frederick's sentence should be lessened due to mitigating circumstances, explaining that few individuals can resist the powerful situational pressures of a prison, particularly without proper training and supervision. The judge apparently disregarded Zimbardo's testimony and gave Frederick the maximum 8-year sentence. Zimbardo drew on the knowledge he gained from his participation in the Frederick case to write a new book entitled, ‘The Lucifer Effect: Understanding How Good People Turn Evil’, about the connections between Abu Ghraib and the Stanford Prison Experiment. (For an Integrated SocioPsychology commentary on the events at Abu Ghraib, see the Blog: ‘Prisoner Abuse & the Mess in Iraq’.)



For more, go to the official Stanford Prison Experiment web site.

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