The method used was an experimental case study. It is a case study because it was a detailed study of a group of people and it was an experiment because a number of interventions (independent variables) were introduced at specific points of the study.
- there was 15 participants
- all male
- all met criteria as decent, normal and well adjusted individuals
- recruited through adverts in the national press
- They were randomly divided into two groups of 5 guards and 10 prisoners
- The guards had a series of means by which to enforce their authority, including keys to all doors inside the prison, sole access to an upper level, a ‘guards’ station’ with a surveillance system from which they could see into the prisoners’ cells, resources (including snacks and cigarettes) to use as rewards or withdraw as punishments – and, in addition, the ability to put prisoners on a bread and water diet.
- The guards also had far better conditions than the prisoners, including superior meals, extra supplies of drinks and snacks, superior living conditions and well-made uniforms.
- The nine prisoners then arrived one at a time. Their heads were shaved, everyday clothes were taken away and they had to shower. The prisoners’ uniform consisted of a t-shirt printed with a 3-digit number, loose trousers and flimsy sandals. They were then put into cells.
- the guards did not develop group identity, they couldn't agree norms and priorities thus they didn't internalise the power role
- until day 3 when 1 prisoner was promoted to guard, individual self interest predominated in prisoners as each prisoner tried to show the qualities that might lead t a promotion
- after day 3 when the roles were fixed the prisoners did develop group identity and as a group challenged the guards, this lead to a shift in power and collapse of the prisoner/guard system
- on day 6 prisoners broke out of cells and the regime of guards was ended. all decided to continue as a self-governing commune but the prisoners who had led the challenge did not co-operate
- by day 8 a more authoriterian system of inequality was being proposed by some. the study ended on day 8.
- permeability of roles - although the guards were told that they had been selected on various criteria, participants were told the tests were not always reliable thus that prisoners could be promoted to guards on day 3
- legitimacy of roles - on day 3 prisoners would be told that there were really no differences between prisoners and guards, but it was impractical to reassign roles thus causing the perception that group differences were not legitimate (this variable was not introduced)
- cognitive alternatives - on the 4th day a new prisoner was chosen because of his background as a trade union official in order to provide the skills required to organise collective action.
ecological validity is (very arguably) low. the prison that was constructed was similar to a real prison but not the same, there were fewer people and the procedures and running was very different.
research validity is arguable again. the fact it was conducted in a controlled setting where extraneous variables can be controlled increases research validity however the study was recorded and broad casted meaning participants may have been behaving differently due to the viewing public.