It was an old social psych study, one of those that rises to prominence in Psych.100 classes. I believe that it was conducted in California, not sure which campus. The aim of the work was to examine how perfectly normal people (soldiers and guards in the German military) could have committed the sorts of atrocities against other people that occurred in the death camps during WWII.
The participants were all college students (as most participants in such studies tend to be) who were randomly assigned to either the prisoner group or the guard group. The study was planned to last for two weeks. Here my memory becomes a bit fuzzy; I can't recall specifically what the instructions were that were given to each group, but responsibility for the guards' actions was apparently explicitly assumed by those conducting the study, and some instructions also were given as to the treatment of the prisoner group.
The study was halted by the sixth day because it had become too brutal. The guard group had become sadistic, and were seriously abusing the prisoner group, though in real life these students were their peers. The prisoner group, likewise, assumed the role into which they had been cast, and not only put up with the abuse, but began to show signs of serious stress and depression. Remember that this whole thing was voluntary, that everyone involved knew at the outset that it was make-believe and that members of both groups were their fellow college students.
The conclusions of the researchers at the time were, simply, that the assumption of responsibility, once removed, from the "guard" group tended to release them to be as brutal and vicious as they were, and that this might have explained the original question of the research. I personally think that this is a pretty simplistic explanation, but given that it was an intro course, it may be that more complex interpretations were not forthcoming at the time to such novices as first-year students. Nevertheless, the behaviors observed were real.
