Protected by anonymity, internet trolls sometimes feel invincible.

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"Why are people so nasty to each other online?" asks Elizabeth Bernstein at The Wall Street Journal. On Twitter, YouTube, Facebook, and pretty much every other website on the internet, comment threads can devolve into petty, mean-spirited shouting matches. In other words, perfectly reasonable people turn into rude jerks. Why?

According to Bernstein:

Anonymity is a powerful force. Hiding behind a fake screen name makes us feel invincible, as well as invisible. Never mind that, on many websites, we're not as anonymous as we think — and we're not anonymous at all on Facebook. Even when we reveal our real identities, we still misbehave.

According to soon-to-be-published research from professors at Columbia University and the University of Pittsburgh, browsing Facebook lowers our self control. The effect is most pronounced with people whose Facebook networks were made up of close friends, the researchers say.

Most of us present an enhanced image of ourselves on Facebook. This positive image — and the encouragement we get, in the form of "likes" — boosts our self-esteem. And when we have an inflated sense of self, we tend to exhibit poor self-control.

Read the entire article at The Wall Street Journal.