Aim: if it was the characteristics of an individual that led to a behaviour, or the situation they were in. Procedures: Mock prison set in the basement of a psychology department. Male student volunteered to take part. Most stable one were chosen. Prisoners: given a number. Guards: given glasses, uniforms, whistles. Findings: Slow start but the prisoners became increasingly brutal. Some even worked unpaid hours. Within 2 days the prisoners rebelled against the guards. After the rebellion was put down the prisoners became depressed and anxious. The 14 day experiment had to end in 6 days. Conclusion: the power of situation to influence people's behaviour as all the prisoners and guards conformed to their roles as they were in a real prison.