Psychologist Philip Zimbardo conducted an experiment in 1971 in which volunteer prison guards dealt with volunteer prisoners. The study had to be stopped due to the level abuse dished out.

Zimbardo talked to Wired about the pressure at Abu Graib that led guards to acts of cruelty at the Iraqi prison:

he situational forces that were going on in [Abu Ghraib] - the dehumanisation, the lack of personal accountability, the lack of surveillance, the permission to get away with antisocial actions - it was like the Stanford prison study, but in spades.

The Guardian’s Matthew Weaver provides info and links as a new round of Abu Graib abuse reports is released.