Are nasty comments contagious?

Yes, the first few responses to online posts set the tone, for better or worse.

When the top comments below an online article are rude, uncivil or disrespectful, later comments tend to follow suit.

In two large experiments, participants who were randomly assigned to see nasty comments below a news article were more likely to post nasty comments themselves, compared to participants who saw civil comments or no comments at all. The same pattern plays out on real news sites. Researchers analyzed 16 million comments on and found that any given commenter was more likely to troll if earlier commenters had trolled.

There are a couple likely explanations. Exposure to nasty comments might set a social norm that incivility is okay or even rewarded. It might also activate negative emotions, which in turn can prompt nastiness.

Luckily, civility seems to be contagious too—comments that model polite disagreement encourage the same tone in future posts.

So to keep trolling to a minimum, online forums should make sure respectful comments rise to the top of threads while limiting the visibility of nasty comments.

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