The Stanford Prison Experiment was a study conducted in 1971 by psychologist Philip Zimbardo that investigated the psychological effects of perceived power and roles on participants. 24 male college students were randomly assigned to be either guards or prisoners in a mock prison set up in the basement of the psychology building at Stanford University. The experiment was intended to last two weeks but was stopped after only six days as the guards began to exhibit increasingly cruel behavior towards the prisoners, including physical and emotional abuse. The findings supported the situational hypothesis that the prison environment itself was the primary cause of the escalating brutality rather than any dispositional traits of the individuals involved. The experiment raised serious ethical issues around informed consent and protecting participants from psychological harm.