I am writing about people who degrade and humiliate others, and I'm looking for related research. Right now, I"m mostly interested in the victimizers, not the victims. Why does a person engage in these behaviors? The cruelty could be in the context of interpersonal violence, child abuse, sexual assault, bullying, torture, war crimes. I'm sure other contexts, too. All articles or book names or theoretical ideas will be most appreciated, in English, Spanish or Portuguese. Thank you!