Ever wonder what is really motivating you to hit "retweet," "like," or "share"? According to new research that will no doubt prompt viral-marketing departments to quick action, we share something because, for whatever reason, its ignites powerful emotions—good or bad—that arouse your nervous system.

Jonah Berger, the University of Pennsylvania professor behind the new study, has previously looked at which emotions resulted in the most email sharing of stories from The New York Times. This early work suggested that both good and bad emotions could result in something going viral, so Berger wanted to dig a little more into why—data that could actually help fashion better viral campaigns.

Berger did two experiments. First he asked 93 students to finish two unrelated tasks: Watch a sequence of video clips that made them either nervous or amused or sad or calmly satisfied. Then, they were shown a clip carefully chosen to be emotionally neutral (so the focus of the test was on the video clips), and asked whether they'd share it with family and friends. Other groups were asked to either sit still or jog for a minute before reading an online news article, and were then told they could send it to anyone they liked, if they so chose.

The result of both tests was the same: If something results in higher physiological "arousal" because of action or emotional stimulus, then you're much more likely to share it—it's actually built into our nervous system, working unconsciously.

This results in big implications if you're trying to get a message shared on a social network. It's all about attaching the right kind of emotional label to the message, whether you're pushing a new branded product or trying to effect a change in people (like giving up smoking). Either infect your audience with some righteous anger, or keep 'em laughing, and they'll be much more inclined to click "retweet" or "share" than if you make them slightly depressed or—and this is the big one—placidly content with your nice product or service.

The mechanism why isn't immediately obvious, though it's not such a leap to guess that it harkens back to an evolutionary stage when communication among human groups was much more basic. And we've all felt it when engaging with Facebook or Twitter or even chatting with colleagues—even if the emotion we're feeling is bad rather than good, we're more inclined to discuss an event or juicy bit of gossip if it's "dramatic" enough to get our bile up or make us spit seltzer out our noses.

Cue the hyper-emotional Twitter campaigns in 3... 2... 1...

Republished with permission from FastCompany.com. Authored by Kit Eaton. Photo via Shutterstock.com.