Critical discussion of the Stanford prison experiment
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Dec 16th, 2019

Critical discussion of the Stanford prison experiment

The Stanford prison experiment (1971) continues to be relevant in psychology for various reasons. Zimbardo attempted to study the development of norms and effects of social roles and expectations on healthy average men by simulating a prison. It resulted in mental breakdowns, abusive and sadistic behaviour among prison guards and was terminated well ahead of schedule.

A study that was prior approved by ethical bodies, it has been criticised for unethical and unscientific methods – leading the way for significant changes in ethical standards of for psychological research. Further, results of the study have contributed to development of various theories and concepts in social psychology.

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The Stanford prison experiment is an important study in the history of social psychology for experts and laymen. Zimbardo (1971) designed the study to understand development of norms and effects of social roles and expectations on ‘normal’, healthy and otherwise average men by simulating a prison environment as accurately as possible. The study was conducted at Stanford and funded by a grant from the U.S. Office of Naval Research to study antisocial behaviour and conflict among prisoners and military guards.

Details of the Study

Advertisements for a study on the psychology of imprisonment, offering $15 per day, were used to recruit twenty-four male students with no prior criminal arrests, medical conditions or psychological disorders. They were randomly assigned prisoner or prison guard roles in a mock basement prison (Zimbardo, 1999). Prison guards were briefed regarding preservation of law and order, avoiding corporal violence and preventing prisoners from escaping etc. Prisoners were arrested in their home – handcuffed, searched and driven away by police – and charged with burglary or armed robbery (Leithead, 2011). They had to follow strict rules, such as silence during rest hours, eating at meal times, cleaning prison cells etc. The prisoners were allowed to quit and though some did, many seemed to forget that they could leave via straightforward procedures. Nearly 50% of prisoners were released ahead of schedule due to extreme emotional disturbance (Zimbardo, 1999).

Interestingly, personality did not predict/distinguish between levels of abusiveness among guards, as did situational characteristics (Dean, 2007; Zimbardo, 2007). Participants became entirely involved in their ‘new life roles’ – suffering mental breakdowns and guards becoming so abusive and sadistic that the study was terminated within six days, rather than two weeks (Zimbardo et al., 1999).

Relevance in the Present Day

“…[A] classic demonstration of the power of situations and systems to overwhelm good intentions of participants and transform ordinary, normal young men into sadistic guards or for those playing prisoners to have emotional breakdowns.” – Prof Zimbardo (Leithead, 2011).

This study highlights various issues that are still relevant to the present day. Results arguably demonstrated the obedience and malleability of people given legitimizing dogma and adequate institutional/collective support, cognitive dissonance theory and power of authority. Situational characteristics affected participants’ behaviour, rather than personal characteristics (Zimbardo et al., 1999; Zimbardo, 2007; Dean, 2007).

Though all students signed a consent form prior to participation and the study was cleared by relevant committees at Stanford, Office of Naval Research and the American Psychological Association (Zimbardo et al., 1999), the study is criticised as being unethical and, subsequently, caused a widespread revision in ethical standards (Carnahan & McFarland, 2007). For these reasons, the experiment is often compared to Milgram’s (1961) obedience experiment.


Unmistakeably, the study has paved the way for much understanding in the area of social psychology, especially with regard to power of authority, obedience and situational characteristics over personality. Further, the study’s effect on participants caused ethical standards for research to change significantly. Thus, this study remains highly relevant to the present day.


Carnahan, T., McFarland, S. (2007) “Revisiting the Stanford prison experiment: Could participant self-selection have led to the cruelty?” Personality & social psychology bulletin, vol. 33, no. 5, pp. 603-14.

Dean, J. (2007) Our dark hearts: The Stanford prison experiment, [Online], Available: [29 May 2012].

Leithead, A. (2011) Stanford prison experiment continues to shock, [Online], Available: [29 May 2012].

Zimbardo, P. G., Maslach, C. & Haney, C. (1999) “Reflections on the Stanford prison experiment: Genesis, transformation, consequences, in Blass, T. (ed.), Obedience to authority: Current perspectives on the Milgram Paradigm, Mahwah, NJ: Erlbaum.

Zimbardo, P.G. (1999) The Stanford prison experiment, [Online], Available: [29 May 2012].

Zimbardo, P.G. (2007) The Lucifer effect: Understanding how good people turn evil, New York: Random House.

Zimbardo, P.G. (n.d.) The psychology of power and evil: All power to the personTo the situationTo the system[Online], Available: [29 May 2012].

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