The Stanford prison experiment (SPE) was a psychological experiment performed during August 1971. It was a two-week simulation of a prison environment that examined the effects of situational variables on participants' reactions and behaviors. Stanford University psychology professor Philip Zimbardo managed the research team who administered the study. Participants were recruited from the local community with an advertisement in the newspapers offering $15 per day ($113 in 2023) to male students who wanted to participate with a "psychological study of prison life".
https://en.wikipedia.org/wiki/Stanford_prison_experiment