October 28, 2009, Harvard University — Psychologists have found that the more a person appears to suffer when tortured, the guiltier they are perceived to be. According to the researchers, those complicit with the torture need to justify the torture, and therefore link the victim's pain to blame.
The full paper, which seems to have been published in 2010, even though the summary is from 2009(???), is: "Torture and judgments of guilt," by Kurt Gray and Daniel M. Wegner.
Full study is free to read here
So if you are ever arrested and mistreated, try to act stoic, I guess.
It's easy to see how this phenomenon could lead to spiraling sadism and abuse, as the abuser lashes out in hatred to bury their increasing guilt.
the study participants were randomly placed in the complicit or the uninvolved groups, presumably there wouldn't have been a major ideological difference between the groups. the two variables were the apparent pain of the actor and the participants' complicity in that pain. the complicit group was more sure of the actor's guilt when the actor expressed more pain, while the distant group was more sure of the actor's innocence when the actor expressed more pain.