Since nobody mentioned that study yet I will.
Canadian scientists have found a correlation between what they call the dark tetrad of personality traits: narcissism, Machiavellianism, psychopathy, and sadism and the behavior of trolls on the 'net.
I must say I wouldn't be that surprised it were actually true especially when you see how some threads get easily derailed in here.
More details in this article:
Keep up the good work. Something worth considering: the control group was random students, not diagnosed sociopaths. It has been shown that the less emotional cues and body language a person perceives, the less likely he is to feel empathy for a person. Off the top of my head: check the variations of Milgram experiment on obedience and authority. It's a pretty old experiment but it's well-known.
But still even if they're trying to build a mythology around them and even if they're using a fake persona.
Their interaction on the 'net is with real people so I think the study felt that it would be legitimate to evaluate them as if they were flesh-and-blood persons because everybody has at least part of their real persona embedded in their internet persona.
As for the Milgram experiment I find it fascinating. One of its objective was trying to understand how perfectly 'normal' people could be transformed into monsters through compliance to orders (it was done post-war so they were trying to understand the nazi machinery).
But they also proved that most everybody has a sadist in them.
Derren Brown re-did it recently with pretty much the same results and as matter of fact he does all kinds of mindfuck experiments on people.
