In 1961, the American psychologist Stanley Milgram began a series of controversial experiments on ‘obedience to authority’. His study aimed to show how ordinary people could be capable of committing evil acts, if ordered to do so. He wanted to understand the psychology behind genocide, telling the BBC: “How is it possible that ordinary people who were courteous and decent in everyday life, can act callously, inhumanely, without any limitations of conscience?” During the tests, participants were led to believe that they were assisting an unrelated experiment, in which they had to administer electric shocks to another person. These fake shocks gradually increased to levels that would have been harmful had they been real volunteers. Vicky Farncombe looks back at the experiment, using BBC archive. This programme includes original recordings of the experiments which listeners may find disturbing. (Photo: Stanley Milgram beside the shock generator. Credit: BBC)