A recent study confirms what we already knew: Internet trolls aren't nice people.

The term "troll" is Internet slang for a person who posts inflammatory or off-topic online comments with the aim of disrupting the conversation and creating discord.

What kind of people go out of their way to anger and offend others? Narcissists, psychopaths and sadists, according to science.

What makes a troll

University of Manitoba researchers conducted two studies to investigate whether people involved in trolling have traits that fall into the so-called Dark Tetrad of personality.

These traits include narcissism (self-obsession), psychopathy (lack of empathy), sadism (taking pleasure in others’ suffering) and Machiavellianism (manipulation and deception of others).

Researchers had more 1,200 participants take personality tests and then complete a survey about their Internet commenting behavior.

One way trolls were identified was by simply asking participants what they enjoyed doing most on commenting sites. Choices included: debating issues, chatting with others, making new friends and trolling.

While most participants (41 percent) identified themselves as "non-commenters," 6 percent said they most enjoyed trolling, and Dark Tetrad scores were highest among this group.

Researchers also found a relationship between the amount of time spent making online comments each day and all the Dark Tetrad traits, with the exception of narcissism.

Study participants were also asked if they agreed with certain statements that researchers compiled under the name of the Global Assessment of Internet Trolling (GAIT). These statements included the following:

I have sent people to shock websites for the lulz.

I like to troll people in forums or the comments section of websites.

I enjoy griefing other players in multiplayer games.

The more beautiful and pure a thing is, the more satisfying it is to corrupt.

Agreeing with these statements correlated with various Dark Tetrad traits, but overall, the strongest relationship was found between trolling and sadism.

"Both trolls and sadists feel sadistic glee at the distress of others," researchers wrote in their paper, which was published in the journal Personality and Individual Differences. "The associations between sadism and GAIT were so strong that it might be said that online trolls are prototypical everyday sadists."

Changing commenting policies

Some media outlets have removed their comment sections to prevent trolling. Anonymous Account/flickr

Trolling has become such an issue that some websites are altering their commenting policies — and in some cases, they’re getting rid of comment sections altogether.

In 2013, YouTube took steps to combat trolling by giving content creators more power to moderate and block comments. And in 2014, the Chicago Sun-Times and the other titles in the Sun-Times Media quit running comments with articles.

"As anyone who has ever ventured into a comment thread can attest, these forums too often turn into a morass of negativity, racism, hate speech and general trollish behaviors that detract from the content," the group said in a statement.

If you've ever been curious about where online trolls live, Wired recently published an interactive map that shows the least and most trollen-ridden places in the United States. Click over to see for yourself, but here are a few highlights:

Vermont has the highest percentage of "crummy comments."

New Hampshire, right next door, has the lowest percentage of mean comments.

Park Forest, Illinois, takes home the title of most-toxic commenters in America.

The small town of Sharpsburg, Georgia, is home to the least-toxic commenters.

Trolls are bad for science

A 2013 study found that trolls rarely change the minds of people they interact with. In short, trolling simply reaffirms people’s pre-existing beliefs. Tero Vesalainen/Shutterstock

Popular Science completely got rid of its commenting section because "comments can be bad for science."

"A politically motivated, decades-long war on expertise has eroded the popular consensus on a wide variety of scientifically validated topics," content editor Suzanne LaBarre said in a statement. "Everything, from evolution to the origins of climate change, is mistakenly up for grabs again. Scientific certainty is just another thing for two people to ‘debate’ on television."

A 2013 study by researchers from George Mason University Center for Climate Change Communication found that trolling polarizes audiences.

In the study, participants were asked to read an article containing a balanced discussion of the risks and benefits of nanotechnology, a fairly noncontroversial topic. All participants read the same post, but the tone of the comments varied. Some were civil, while others were rude.

Participants who read the article with derogatory comments became more sure of their own views on nanotechnology when exposed to arguments and name-calling. In short, trolling simply reaffirms people’s pre-existing beliefs.

This makes sense if you look at how our brains work.

Our feelings about people and ideas arise faster than our conscious thoughts, which has helped our species survive by enabling us to quickly respond to our environment.

Essentially, our fight-or-flight reflexes protect us from both unfriendly information as well as predators.

Researchers didn’t study climate change trolls directly, but they note in their paper that "the controversy that you see in comments falls on more fertile ground [than nanotechnology], and resonates more with an established set of values that the reader may bring to the table."

In short, if you don’t want to be influenced by inflammatory remarks, skip the comments section altogether. And, of course, don't feed the trolls.

Members of Climate Desk, a journalistic collaboration that explores the impact of climate change, has its own way of dealing with trolls. In the video below, Climate Desk journalists take a trip to meet their top troll and learn why he does what he does.