I should note that there are critics (one of my favorite authors, included), who think the famous Stanford Prison Study does NOT explain Abu Ghraib (there's a follow-up here).
QUESTION: You keep using this phrase “the situation” to describe the underlying cause of wrongdoing. What do you mean?
ZIMBARDO: That human behavior is more influenced by things outside of us than inside. The “situation” is the external environment. The inner environment is genes, moral history, religious training. There are times when external circumstances can overwhelm us, and we do things we never thought. If you’re not aware that this can happen, you can be seduced by evil. We need inoculations against our own potential for evil. We have to acknowledge it. Then we can change it.
And as an aside, most academics have come to call the famous Prison research a "study" rather than an "experiment" - no group comparisons, really. No random assignment. No placebo. Just a note to keep in mind.