1) Zimbardo conducted a study in 1973 where male college students were randomly assigned to roles of prisoners or guards in a mock prison set up in the basement of the Stanford psychology building. 2) The guards took their roles very seriously, quickly becoming authoritarian and abusive towards the prisoners to such an extent that the study had to be stopped after only 6 days. 3) Criticisms of Zimbardo's study include that it did not obtain proper informed consent from participants and that it subjected prisoners to humiliation and psychological harm.