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The Stanford prison experiment and its effects

The opinions expressed in this article are the writer’s own and do not reflect the views of Her Campus.
This article is written by a student writer from the Her Campus at Aberdeen chapter.

The Stanford Prison experiment was a social psychology experiment influenced by the Milgram experiment that sought to investigate the psychology of prisoners. The study ran from August 14th, 1971, to August 20th, 1971.

The study aimed to investigate the extent to which people would conform to the roles of guard and prisoner in a role-playing simulation of prison life.

A mock prison was created in the basement of Stanford University. The roles of both guards and prisoners were assigned at random to the participants, with guards wearing khaki uniforms, and reflective glasses to avoid eye contact and they carried wooden batons although they were told no physical aggression was permitted. Prisoners wore numbered smocks, and nylon stocking caps to give the impression of shaved heads and had a chain around one ankle and a routine of shifts, mealtimes etc., as well as visiting times, a parole and a disciplinary board. The prisoners were divided into three to a cell.

The results showed that they adapted to their new roles well beyond what was expected. The guards produced new ways to humiliate the prisoners whilst using physical aggression, such as cleaning toilets with their bare hands, not allowing sanitation buckers to be emptied and removing prisoners’ mattresses. The prisoners tried to rebel, for example, by attempting to escape or refusing orders, but the guards always overpowered them leading to the submission of prisoners. Some prisoners became depressed and anxious with one prisoner having to be released after 36 hours due to fits of crying and rage, with two more leaving on day four and the study being discontinued on day six when it was due to run for two weeks.

Zimbardo felt that deindividuation occurred especially in the prisoner’s case due to complete loss of ‘individuation’ as participants seemed unable to focus on who they were and so fell into the role of being prisoners. This was caused by the humiliation of the arrest and strip-down at the beginning the punishments conducted by the guards and the labelling of the prisoners as numbers also helped this “de-individualisation” process as they no longer felt they had an identity.


One strength of the study was that it altered the way US prisons are run. For example, juveniles accused of federal crimes are no longer housed before trial with adult prisoners, due to the risk of violence against them. The harmful treatment of participants also led to the formal association and now studies must undergo an extensive review by an institutional review board (US) or ethics committee (UK) before they are implemented. Therefore, the study has had real-life applications in protecting prisoners and participants in further studies. Another strength is that there is evidence that the participants reacted to the situation as if it were real. For example, 90% of the prisoners’ private conversations, which were monitored by the researchers were prison-related, and only 10% of the time the conversations were about life outside the prison. When introduced to a priest, they referred to themselves by their prison number rather than their name. The guards rarely exchanged personal information during their breaks and spoke mostly about prison, were always on time and worked overtime for no extra pay. This suggests that the results are representative.

However, there were weaknesses, one weakness is that demand characteristics could explain the findings of the study. For example, most of the guards later claimed that they were simply acting as they realised the aims of the study and wanted to please the researcher. This suggests the results are not valid as it was not measuring what it claimed to measure. Another weakness is that there was low ecological validity as behaviour may not be influenced by some factors which affect behaviour in real life so findings cannot be reasonably generalised to real life. There is a lack of population validity as the sample is comprised of US male students. The study’s findings cannot be applied to female prisoners or those from other countries, as it is an ethnocentric and androcentric sample. Another weakness is that the study broke ethical guidelines. For example, the participants were not protected from psychological harm, which is shown by the pathological effects. Some participants felt, for example, some becoming depressed and anxious, with one participant leaving after just 36 hours. therefore, the study faces ethical issues.

The study concluded that circumstances informed people’s behaviour and attitude. The prisoners and the guards conformed to their respective roles.

Hello! I am a third-year student studying English and International relations at the University of Aberdeen. I enjoy reading and photography.