Milgram's book describes the landmark psychology experiment he conducted as a young researcher at Yale in the 1960s. He recruited volunteers to give "electric shocks" to learners whenever they answered a question wrong. The volunteers didn't know these subjects were not actually being shocked. To widespread surprise, Milgram reported that 40 to 65 percent of his volunteers did what the researcher told them, and gave the maximum shock to the "learners" even when they screamed in pain. His experiment showed that ordinary people tend to obey authority, and helped explain the psychological mechanisms that lead people to participate in cruel and inhumane events such as the Holocaust.