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.
i think you're missing a sense of the process here: someone is presumed guilty --->expressing pain means the torture is working, they are going to admit the truth because Jack Bauer placed their hand on a stove and they screamed.
let me explain this in a less abstract way: an example of torture as regularized procedure was enacted by the inquisition(s) of medieval/early modern europe in response to heresy. it was not to determine if the victim was heretical, that was established with hearings & testimony of witnesses. torture was for the confession and the repudiation & reconciliation with the mother church (failing that, an execution) you got to the point where they were torturing you there was no 'oops they were innocent all along'
kind of losing the plot about the relationship with the study to this but i hope this helps with how pain & torture logically connect to guilt in a pro-torture paradigm
In that scenario, they are already 100% assumed to be guilty before the torture even starts. Expressing pain does not increase the perception of guilt, just the expectation that they are going to say something. This isn't a study about whether participants think a guilty person will talk or not, but about whether the person is actually guilty at all.
sorry if I'm being obtuse or still missing the point