Prof Phil Zimbardo, creator of the Stanford Prison Experiment: In 1971 I became superintendent of the Stanford Prison, a mock prison. I was a young psychology professor at Stanford University. I wanted to understand what happens when you put good people in a bad place. [We] selected college-student volunteers - normal, healthy young men with no history of crime or violence - and randomly assigned them the roles of prisoner or guard. To increase the real-life feel, we arranged for actual mass arrests and booking by the Palo Alto police; visits by a prison chaplain, a public defender, and parents. Though not part of the plan, there were also prisoner rebellions. And, notoriously, there was chilling abuse and torture by the guards. The experiment was supposed to last two weeks, but we had to pull the plug after only six days because nearly half the prisoners had emotional breakdowns. Fast-forward to April 2004. Horrific images flash across our television screens - nightmarish abuses of Iraqi prisoners by young American soldiers. The images were ... strikingly similar to what I had seen at Stanford - prisoners naked, bags over their heads, forced into sexually humiliating poses. Historical inquiry and behavioural science have demonstrated ... that given certain conditions, ordinary people can succumb to social pressure to commit acts that would otherwise be unthinkable. In the prisons at Stanford and Abu Ghraib, men and women did terrible things to other people in part because responsibility for their actions was diffused. We find ourselves in a similar situation whenever we witness someone else's trouble but fail to help because we assume others will."