In the Stanford prison experiment, who served as the principal investigator?

Philip Zimbardo served as the principal investigator of the Stanford prison experiment.

The study began in August 1971 at Stanford University. Male college students were randomly assigned to act as prisoners or guards in a simulated prison built in the psychology department. Zimbardo led the research team and also took the role of prison superintendent.

The planned two-week study was stopped after six days because of increasingly distressing behavior and concerns about participants' welfare. The experiment became widely cited in discussions of authority, social roles, and institutional settings.

Later scholars have challenged both the study's methods and some of its interpretations. Accounts indicate that researchers gave guards instructions that may have shaped their conduct, so the experiment is no longer treated as straightforward proof that assigned roles alone determine behavior.