What makes ordinary people do evil things? It was a question that long fascinated the psychologist Philip Zimbardo, who died in October. Zimbardo was best known for the controversial Stanford prison experiment, in which he created a simulated prison in the basement of a university building and recruited volunteers to act as prisoners and guards. This week, we explore how Zimbardo came to create one of psychology's most notorious experiments – and inadvertently became the poster child for the human weaknesses he was trying to study.

We're bringing Hidden Brain to the stage in San Francisco and Seattle in February 2025! Join our host Shankar Vedantam as he shares seven key insights from his first decade hosting the show. Click here for more info and tickets.