Anyone who's ever encountered internet trolls - vile, racist, sexist and often profane people who delight in other people's misery - might have concluded that they are psychologically disturbed.
That would be correct, new research suggests. Trolls gleefully send out their "e-bile" using smartphone apps, online comments, texts or social media sites for no other reason than cruelty.
"I get stuff on the text line all the time, where people swear at me and call me the foulest names ... It's easy to throw something out there when you're anonymous. That is the thing about the internet, especially about trolls. Most of these people are cowards."
However, a recent paper by a team of Canadian researchers, who have looked into the psychological underpinnings of trolls, suggests the trolls may be something else as well - sadists.
Yet not the psychopathic sadists who turn to actual physical torture or serial killing.
"We use the term 'everyday sadist' to emphasise that we are referring to sub-clinical levels of sadism, and not the more extreme forms that are seen in serial killers and criminals," says psychologist Erin Buckels, of the University of Manitoba, in Winnipeg, one of three authors of a paper on troll personality published in the journal Personality and Individual Differences.
"The essential aspect of sadism is enjoyment of cruelty," Buckels says. "Persons high in sadism gain some emotional benefit from causing or simply observing others' suffering."
Although researchers delineate between cyberbullies and trolls - cyberbullies torment specific individuals and are often known by their victims, while trolls like to cast their hurt about - they are linked by their special liking for cruelty.
In their troll research, Buckels, Manitoba colleague Paul Trapnell and Delroy Paulhus, of the University of British Columbia, gathered data from 1,215 individuals - half men and half women - based on answers to two online surveys.
Both surveys included questions about the subjects' internet habits, such as, "How many hours per day do you spend posting comments?", or, "What do you enjoy doing most on these comment sites? Debating issues, chatting, trolling, making new friends, something other?".
The surveys also included statements from well-known diagnostic tests of personality traits meant to detect various levels of sadism: "Hurting people is exciting", or "In video games, I like realistic blood spurts".
Beyond sadism, the questionnaire also looked for signs and varying levels of what are known as the three other legs of the "dark tetrad" of personality.
These are narcissism (I have been compared to famous people); sub-clinical psychopathology (payback needs to be quick and nasty) and Machiavellianism (it's not wise to tell your secrets).
The conclusion is that those who are rated highest on the scales for narcissism, psychopathology, Machiavellianism and sadism - highest of all for the trait of sadism - were the same people who were trolls.
Enjoyment of other online activities, such as chatting and debating, was unrelated to sadism, the researchers found.
"It seems like one of their great joys in life is to make fun of other people and to criticise their opinions," Paulhus says.
Paulhus says that trolls are often insatiably nasty; there is no way to reason with them. The more havoc they create - getting more people to argue with them - the happier they become. It is this well-known trait that has given rise to the internet advice, "Don't feed the trolls". Like ravenous strays, they simply come back.