Stanford Magazine looks at Philip Zimbardo's famous "prison experiment", forty years later. The Prison Experiment ranks with the Milgram experiment as a classic study of how authority corrodes ethics, demonstrating how otherwise normal and decent human beings can become abusive monsters when handed power.
Here are some choice quotes from participants in the experiment:
"The prison study has given me a new understanding of what 'heroism' means. It's not some egocentric, I'm-going-to-rush-into-that-burning-building thing—it's about seeing something that needs to be addressed and saying, I need to help and do something to make it better." -- Christina Maslach, who stepped in to insist that the experiment be stopped
"When the Abu Ghraib scandal broke, my first reaction was, this is so familiar to me. I knew exactly what was going on. I could picture myself in the middle of that and watching it spin out of control. When you have little or no supervision as to what you're doing, and no one steps in and says, 'Hey, you can't do this'—things just keep escalating. You think, how can we top what we did yesterday? How do we do something even more outrageous? I felt a deep sense of familiarity with that whole situation." -- Dave Eshelman, described as the prison's most abusive guard
"It really was a unique experience to watch human behavior transform in front of your eyes. And I can honestly say that I try never to forget it. I spend a lot of time with real prisoners and real guards, and having seen what I saw then, while a graduate student, gave me respect for the power of institutional environments to transform good people into something else." -- Craig Haney, a graduate student researcher
"One thing that I thought was interesting about the experiment was whether, if you believe society has assigned you a role, do you then assume the characteristics of that role? I teach at an inner city high school in Oakland. These kids don't have to go through experiments to witness horrible things. But what frustrates my colleagues and me is that we are creating great opportunities for these kids, we offer great support for them, why are they not taking advantage of it? Why are they dropping out of school? Why are they coming to school unprepared? I think a big reason is what the prison study shows—they fall into the role their society has made for them." -- Richard Yacco, one of the prisoners
You can read more about the Prison Experiment at Wikipedia and at the Prison Experiment website.
You also ought to check out Zimbardo's "Heroic Imagination" project, which seeks to "provide the knowledge, tools, strategies, and exercises to help individuals overcome the inertia which keeps them from taking positive action at crucial moments in their lives...[to] train individuals to transform their innate desire to do the right thing, into the ability to actually do it."