What’s the psychology of trolls?

From Slate: "A new psychology paper (writes) about the personalities of (online) trolls. … The research, conducted by Erin Buckels of the University of Manitoba and two colleagues, sought to directly investigate whether people who engage in trolling are characterized by personality traits that fall in the so-called Dark Tetrad: Machiavellianism (willingness to manipulate and deceive others), narcissism (egotism and self-obsession), psychopathy (the lack of remorse and empathy), and sadism (pleasure in the suffering of others)."