Human history is littered with brutal campaigns of torture and murder committed by one political or religious group against another. These atrocities are not limited to the dusty old pages of history books. Over the last 100 years, we have witnessed the Holocaust, as well as genocidal campaigns in the former Yugoslavia, the Darfur region of Sudan, and many other places around the world. It is comforting to think that coordinated murder campaigns like the Holocaust can be blamed on a single monstrous individual like Adolf Hitler. But it is important to remember that although Hitler orchestrated the Holocaust, many individuals helped carry it out. Were all of the people who participated in the killing mentally ill? Could "regular," healthy, "good" people participate in these kinds of atrocities? This was the question on the mind of Stanley Milgram when he conducted his famous obedience studies in the 1960s. You may have a hard time believing how easy it was to convince regular, everyday citizens with no history of mental illness to inflict painful electric shocks on another person. Yet that is the legacy of the Milgram study: it would appear that we are all capable of harming others if an authority figure asks us to do so.