Reddit tried an experiment to curb hate speech. The results are fascinating.

In 2015, Reddit decided to run some of the haters out of town.

Image by Rebecca Eisenberg/ Upworthy.

The “homepage of the Internet, ” known for its wholesale embracing of free debate, banned several of its most notorious forums, including r/ coontown, a hub for white supremacist gags and propaganda, and r/ fatpeoplehate, a board on which users heaped abuse on photos of fat people.

Critics accused the site of axing the subreddits for the “wrong” reasons — demonizing unpalatable speech rather than incitement to violence. Others fretted the ban would be ineffective. Wouldn’t the trolls merely spew their dislike elsewhere on the site?

Thanks to a group of Georgia Tech researchers, we now have evidence that the ban worked.

Their paper, “You Can’t Stay Here: The Efficacy of Reddit’s 2015 Ban Examined Through Hate Speech ,” found that not only did banning the forums prompt a large portion of its most dedicated users to leave the site entirely, the redditors who did remain “drastically[ lessened] their dislike speech usage.”

The researchers investigated over 650 million submissions and remarks posted to the site between January and December 2015. After arriving at a definition for “hate speech, ” which they determined by pulling memes and phrases common to the two shuttered forums, they find an 80% drop in racist and fat-phobic speech from the users who migrated to other subreddits after the ban. 20 -4 0% of accounts that frequently posted to either r/ coontown or r/ fatpeoplehate became inactive or were deleted in that reporting period.

“Through the banning of subreddits which engaged in racism and fat-shaming, Reddit was able to reduce the prevalence of such behaviour on the site, ” the paper’s writers concluded.

The researchers have a few hypothesis about why the ban may have worked.

Those who migrated to other subreddits, they speculate, became beholden to exist community norms that restricted their ability to speak detest freely.

Reddit co-founder and executive chairperson Alexis Ohanian. Photo by Jerod Harris/ Getty Images.

They also cite Reddit’s effective removal of copycat forums( r/ fatpeoplehate2, r/ wedislikefatpeople, etc .) before they could reaching critical mass.

Creating secure online spaces is a difficult problem. This new research offer at least one possible answer.

Any attempt to moderate an open web forum, the researchers argue, will inevitably have to balance protecting free expression with the right of people to exist on the internet without fear of abuse. A June Pew research poll found that 1 in 4 black Americans reported having been harassed online because of their race, compared with 3% of white Americans.

“The empirical work in this paper suggests that when narrowly applied to small, specific groups, banning deviant detest groups can work to reduce and contain the behaviour, ” the authors wrote.

For vulnerable people who, like most, are living increasingly online lives, it’s a small measure of relief.

Correction 9/13/ 17: This tale was updated to identify Alexis Ohanian as Reddit’s co-founder and executive chairwoman , not CEO.

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