My brother and I have a childhood history of internet trolling under our belts. Innocent enough, yes – but disruptive nonetheless. From the same room at our parents’ house, we’d play Yahoo! Graffiti (the internet’s version of Pictionary). The word was “dinosaur” and it was his turn to draw. He’d illustrate a beautifully elaborate rainbow. All the while, players would be guessing “rainbow,” “RAINBOW,” “RAINBOW!!!” and wonder why they weren’t scoring points. I’d wait until five seconds were left on the clock and finally, calmly, contribute “dinosaur”. We’ve been banned from Yahoo! Gamerooms until 2016. (With any luck, I’ll have my PhD by then and show Yahoo! that I’m a changed woman.)

A “troll”, in internet slang, is someone who deliberately upsets others by starting arguments or posting unnecessarily inflammatory messages on blogs, chatrooms, or forums. In recent years, it’s gotten so bad that YouTube needed to develop a way for users to moderate their video’s comments section, and Popular Science shut down its comments section entirely. Indeed, for trolls, the anonymity of the internet is the perfect playground.

But a new study by Erin Buckels and colleagues at University of Manitoba in Canada wanted to figure out who, exactly, these trolls are. Using Amazon’s Mechanical Turk website, internet users (mostly male, with an average age of 29 years) answered survey questions designed to assess what’s called the “Dark Tetrad of personality”. This tetrad includes narcissism (egocentrism and preoccupation with prestige), Machiavellianism (tendency to deceive and manipulate), psychopathy (lack of empathy and inhibition), and sadism (pleasure of inflicting pain or humiliation on others).

Buckels and colleagues asked about the participants’ internet behavior, including how frequently they comment on blogs and forums. They also gauged how the subjects commented, asking whether they preferred debating, chatting, making friends, or trolling. Of the 418 participants, 59% said that they actively comment on websites. Among those, nearly a tenth admitted that their favorite activity was trolling other users.

Scores on the Dark Tetrad personality test revealed that trolls are, by far, more likely to have narcissistic, Machiavellian, psychopathic, and sadistic personality traits. Okay, so that’s not so surprising. But Buckels and colleagues wanted to take it a step further: how much enjoyment are these trolls getting from their online shenanigans? The researchers constructed their own Global Assessment of Internet Trolling (GAIT), which asked such questions as “I have sent people to shock websites for the lulz” and “The more beautiful and pure a thing is, the more satisfying it is to corrupt.” (Sadly, some people indeed answered these questions with a “yes”).

Trolling enjoyment was very strongly associated with a sadistic personality, and was also correlated with Machiavellianism and psychopathy. In fact, further statistical analysis revealed that most of the Dark Tetrad correlations with internet trolling were because of overlap with sadism.

So basically, the study shows that people write nasty comments because they enjoy harming others. Big deal, right?

Actually, the study may have some interesting implications. Since a sadistic person is characterised by being vicious and degrading toward others (sometimes physically), it’s possible that the internet allows them to redirect their energy. If they’re inflicting harm through anonymous words, perhaps it’s preventing them from doing something much more destructive in person. On the extreme end, and unsurprisingly, sadism is commonly seen in sexual offenders and serial killers.

Another finding that was not emphasised strongly in the paper: across all participants, the average amount of time they admitted devoting to commenting was over an hour a day. AN HOUR! Commenting frequency was associated with younger age, being male, and high scores on the authors’ GAIT test. If you have a friend who spends upwards of an hour of their day remarking on friends’ Facebook photos, replying to everyone’s tweets, or making memes for the subreddit Advice Animals – whether pleasantly or savagely – perhaps it’s time to gently prod them in another direction.

So the next time you find yourself reeling over a particularly hateful comment on your favorite website, take some comfort in knowing that you’re just another anonymous pawn in the internet troll’s game. They’ve got some serious personal issues going on that they might not even realise.

Or it’s just another 12-year-old trying to ruin your Yahoo! Graffiti experience. That’s possible, too.