There was another study I've read as well, these are great for understanding the behavior of staff.
According tot he other study I read, 1/3 of prison guards will 'be nice' or treat prisoners with respect and dignity, another third will be indifferent, and the final third are sadistic, meaning they use the control over the prisoners for their own amusement and stress relief... and to get their sick jollies off. But... for some reason... humans are just NOT MEANT to have this kind of control over other human beings without turning into monsters. Seems to be a part of our psyche.