The Stanford Prison Experiment, conducted by Philip Zimbardo in 1971, is one of the most well-known and controversial experiments in psychology. The experiment aimed to investigate how individuals conform to social roles and the effects of power dynamics on behavior. While there are many theories that attempt to explain the results of this experiment, one theory that seems particularly relevant is Social Identity Theory.

What is Social Identity Theory?

Social Identity Theory (SIT) is a theory that explains how individuals define themselves based on their group membership and how this affects their behavior. According to SIT, people tend to categorize themselves and others into social groups based on shared characteristics such as race, gender, religion or nationality. This categorization leads people to identify with their group and distinguish it from other groups.

The Stanford Prison Experiment

Zimbardo’s experiment involved 24 male participants who were randomly assigned to be either guards or prisoners in a simulated prison environment. The experiment was supposed to last for two weeks but had to be terminated after only six days due to the extreme behavior exhibited by both groups.

The guards quickly became authoritarian and abusive towards the prisoners, using tactics such as physical punishment, psychological manipulation, and forced nudity. The prisoners began showing signs of extreme stress and anxiety, with some even experiencing emotional breakdowns.

How Does SIT Apply?

Social Identity Theory provides an explanation for why the guards acted in such an extreme manner towards the prisoners. As guards, they were given a specific role within the prison environment which made them feel powerful and superior over the prisoners. This sense of power led them to identify more strongly with their group (guards) than with the prisoners’ group.

In contrast, the prisoners were stripped of their individual identities upon entering the prison environment and were instead defined solely by their group membership (prisoners). This led them to identify more strongly with their group than with the guards’ group. This intergroup dynamic created a situation in which the guards felt entitled to exert their power over the prisoners, while the prisoners felt powerless and dehumanized.


The Stanford Prison Experiment is a classic example of how social identities can influence behavior. The experiment showed how people can be influenced by the roles they are assigned and the groups they belong to. Social Identity Theory provides a useful framework for understanding why this occurred, by highlighting how group membership and intergroup dynamics can shape our attitudes and behaviors.

In conclusion, while there are many theories that attempt to explain the results of this experiment, Social Identity Theory is particularly relevant as it emphasizes the importance of group membership and intergroup dynamics in shaping human behavior.