Be careful what you post on Reddit.

If a recent user-run sociological experiment is any indication, users of the social news site hold grudges and have a long memory. That means bad behavior on Reddit may just come back to bite you in your karmic ass.

Redditor reddit_experiment1 spent six months leaving comments from five different accounts, each with its own personality, across the site. He dropped comments in the big subreddits—places more likely to a capture a broad subsection of the site’s population—and then, halfway through, abruptly changed personalities.

He found that his contrarian character—the one who always disagreed with everyone and collected piles of downvotes—couldn’t escape from the karma hole he’d dug for himself. Even after switching to a better personality, the account continued to accrue downvotes.

Reddit_experiment1 chalks that up to followers: People who remembered the guy were pissed off enough that they followed him around and downvoted everything he said, regardless of context. In effect, he’d attracted enemies, and they didn’t give up when his posts suddenly turned nice.

Reddit_experiment1 wrote:

“After switching this account to the more agreeing personality, his upvote:downvote ratio is slowly improving, but the negative followers who consistently downvote everything he posts are having a noticeable effect on his performance, even 3 months into becoming a nicer person. No matter what he posts and what he replies to, he is always received negatively.”

He saw similar effects when switching other personalities: When the nice guy character abruptly switched into being a jerk, his upvotes persisted. People remembered his friendly behavior and rewarded him.

Reddit’s currency is karma—a point system that tallies a user’s total of upvotes minus his or her downvotes. The system’s intended to reward users for good contributions on the site, though it has little practical value beyond bragging rights.

In the thread at r/sociology, redditor Gimli_The_Dwarf had an interesting idea. He suggested that, in its next iteration, the study should employ different people, who would switch account names halfway through.

Others suggested that the trend reddit_experiment1 discovered had more to do with Reddit Enhancement Suite (RES), a third-party browser plugin that keeps track of how many times you’ve voted someone up or down and leaves a tally next to their username.

“After using RES for a while, I’ve started recognizing certain usernames that I often downvote,” redditor RobThursday wrote.

“That recognition probably pushes me toward downvoting their contributions in the future, even if I would have normally abstained from voting or maybe even upvoted if it had been associated with a different username.”

Thanks to RES, the Downvote Effect may have less to do with grudges, and more to do with the fact that users have essentially marked you.

The experiment is actually long from over. Three months from now, reddit_experiment1 plans to switch the accounts back to their original personalities, collect more data, and release his findings (as well as the dummy account names) in December.

At that point his study will be a year old. Let’s hope our collective memories are good enough to give send an upvote his way when the time comes.

Photo by Torley