(PHILIP ZIMBARDO:) For years I've been interested in a fundamental question concerning what I call the psychology of evil: Why is it that good people do evil deeds? I've been interested in that question since I was a little kid. Growing up in the ghetto in the South Bronx, I had lots of friends who I thought were good kids, but for one reason or another they ended up in serious trouble. They went to jail, they took drugs, or they did terrible things to other people. My whole upbringing was focused on trying to understand what could have made them go wrong.