As an Internet writer, I have seen no end to the cruelty that stems from the promise of anonymity. For seemingly benign articles, I have attracted the foulest vitriol from hundreds of commenters, calling me ignorant, stupid, unqualified and more profane nicknames than I care to recall. Message boards like Reddit and 4chan attract the truly evil, where entire message threads exist to belittle and berate, or to raise opinions that are intentionally unpopular for their bigotry and violence (such as the subreddit that seriously addresses the benefits of rape).

Why do trolls behave the way they do? Two studies published in the September 2014 issue of Personality and Individual Differences seek to answer that question. The studies examined personality traits and commenting styles of 1,215 people and found that the trolls had personality traits that exactly lined up with what is known as the “Dark Tetrad” of personality traits: sadism, psychopathy and Machiavellianism, a psychological term used to describe those who manipulate and trick others for personal gain.

Live Science reports:

To conduct the first study, the researchers recruited 418 people, with an average age of 29, to complete survey questions online. One of the measures of sadistic personality used in the study was the so-called Short Sadistic Impulse Scale, which includes 10 items that assess a person’s tendency to enjoy hurting others… In the second study, the researchers constructed another trolling measure that they called the Global Assessment of Internet Trolling (GAIT) scale. They used this tool to assess people’s trolling behavior and levels of enjoyment. They also asked people in the study how much time they typically spent online. The investigators found a link between online commenting frequency and the enjoyment of trolling, which is consistent with previous research that has established an association between excessive use of technology and antisocial behavior.

“Of all personality measures,” the study reads, “sadism showed the most robust associations with trolling and, importantly, the relationship was specific to trolling behavior. Enjoyment of other online activities, such as chatting and debating, was unrelated to sadism.”

Still, the study did not go into cause and effect, so from this study one can glean no more than a strong association between making people suffer online and being a sadist.

While some websites have attempted to mitigate the effects of trolls by doing away with comment sections, study author Erin Buckels isn’t sure that will help. “Because the behaviors are intrinsically motivating for sadists, comment moderators will likely have a difficult time curbing trolling with punishments (e.g., banning users),” she said in an email to Slate. “Ultimately, the allure of trolling may be too strong for sadists, who presumably have limited opportunities to express their sadistic interests in a socially-desirable manner.”