What is it with people’s behavior online? Why the readiness to attack, the snarky tone, the lack of courtesy inherent to so many comments? The internet can bring out the worst in people, which when taken to extremes turns into trolling—that bizarre impulsive habit of hurting others online, without consequence.

Researchers in Australia set out to discover what traits in “normal” people (social media users above age 18 who did not appear to be trolls) might make them susceptible to trolling behavior. Using an online questionnaire, the researchers at the School of Health Science and Psychology at Federation University in Mount Helen tested 415 men and women for a range of personality traits, as well as for online behavior that indicated a propensity to troll—such as agreeing with the statement, “Although some people think my posts/comments are offensive, I think they are funny.”

The researchers were looking for particular traits including social skills, psychopathy, sadism, and two types of empathy: affective and cognitive. Having high cognitive empathy simply means they can understand others’ emotions. Having high affective empathy means a person can experience, internalize, and respond to those emotions. The “trolls” in the study scored higher than average on two traits: psychopathy and cognitive empathy.

So even though “trolls” exhibit one kind of empathy, coupling it with psychopathy ultimately makes them nasty, the researchers suggested. Psychopathy, which includes a lack of care for others’ feelings, was measured using a scale where participants were asked to agree or disagree with a set of statements such as, “payback needs to be quick and nasty.”

High levels of cognitive empathy make these people adept at recognizing what will upset someone, and knowing when they’ve pushed the right buttons. The lack of affective empathy allows trolls not to experience or internalize the emotional experience of their victims.

“Results indicate that when high on trait psychopathy, trolls employ an empathic strategy of predicting and recognising the emotional suffering of their victims, while abstaining from the experience of these negative emotions,” the researchers wrote. They added that because psychopathy is associated with thrill-seeking and impulsivity, it’s possible that “creating mayhem online is a central motivator to troll.” They also found that trolls were likely to be high in sadism—the will to hurt others—and were more likely to be male.

The study is forthcoming in the journal Personality and Individual Differences. It doesn’t offer advice on how to stop trolling behavior, but adds a wrinkle to our knowledge of why people act out online. In previous research, people who display psychopathic traits have shown a similar empathy imbalance: a lack affective empathy but normal levels of cognitive empathy. This study linked those psychopathic traits and higher cognitive empathy levels to people who are likely to troll.

Exploring the link between psychopathy, high cognitive empathy, and trolling could help deepen our understanding of the personality types that gravitate towards that behavior, and potentially help to stop them.