So, there was I was, minding my own business and browsing along on Wikipedia (which I tend to make a habit of, when I started reading about cognitive dissonance for no particular reason. A few clicks later, a came across this article. Go ahead, read it, then come back when you wipe the cold sweat from your brow.
The set up a fake prison with respondents on a prison study. Some were slated to be guards, some slated to be prisoners. There were very few rules, the most notable of which was that you shouldn't physically harm the prisoners if you're a guard. What followed was pure horror: Guards humiliated and psychologically tortured the prisoners. Early on, the prisoners staged a revolt. Eventually, 2 had to leave early because of severe psychological stress, and the experiment was cut short because an outsider began to question the morality of the study.
This study is a strong example of human nature, and our desire to fit within our respective groups. Things spiraled out of hand because of the lack of controls and the fact that the person conducting the experiment was also a participant. But, it shows what happens when people are left to their own devices, with only vague instructions, specifying the need to make life uncomfortable to the imprisoned. It's suggested that some of the behaviors seen at Guantanamo Bay were similar to what was seen in this experiment.
It's also chilling reminder of this statement (I forget who said it first): Power corrupts; Absolute power corrupts absolutely.
Truer words have not been spoken.