A new movie about the Stanford Prison Experiment opens tonight, based on the famous experiment run by psychologist Philip Zimbardo. In 1971, Zimbardo set up a mock prison in a basement of the Stanford Psychology Department, and assigned volunteer students to be prisoners or guards. The experiment was supposed to run for two weeks, but was abandoned after only six days, because the situation was out of control, with guards becoming abusive and prisoners getting distraught. Since then, the study’s conclusion has been widely adopted - that people’s actions are influenced more by the situations they’re in than by their personalities. But now some experts in social psychology are challenging that assumption, and the experiment itself, as invalid science.