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.