Have you ever tried to unravel the mysteries of what makes a blog post or article go viral, capturing readers' interest so that they share it again and again across social media platforms?

To explore this question, the content marketing company Fractl teamed up with content analyzer Buzzsumo. They reviewed shares of 1 million articles from 190 top publishers (including this one) across five social media platforms over six months--2.7 billion shares in all. The findings were thought-provoking (check out the full report at the bottom of this post):

1. Different social media have different moods.

It turns out 70 percent of the 500 most-shared items on LinkedIn were positive in sentiment. Similarly, 65 percent of the top shares on Pinterest were positive. That contrasts with Twitter, where only 40 percent of the top 500 shares were positive, 46 percent were negative, and 14 percent were neutral. Google+ was only slightly more upbeat, with 45 percent positive stories, 38 percent negative stories, and 17 percent neutral.

On Facebook, negative stories were much more successful, making up 47 percent of the top 500 most-shared, with 36 percent positive, and 17 percent neutral. Correct for the relatively uplifting effects of Buzzfeed, Upworthy, and ViralNova, and you have an even darker mood: Only 30 percent of the most-shared stories are positive, and 57 percent are negative.

Does this mean that LinkedIn users are happy-go-lucky souls and Facebook users are incorrigible curmudgeons? Not necessarily, the study's authors warn. "The emotional landscape of each network may be more a reflection of the publishers who are succeeding best at sharing on a particular platform," they note. Still, it seems likely that matching the emotional mood of your content to the prevailing mood of shares on each platform may help you get more attention and more page views.

2. Surprise and mystery always appeal.

Wondering just what sorts of stories or posts will appeal most to readers? Analyzing the pieces' headlines only, the researchers discovered what many readers already know: Pieces that make you go "huh!" as in "I didn't know that," or "huh?" as in "I want to know more," are always the most popular. "Headlines that incorporated surprise and built on the reader's feelings of curiosity dominated the Top 10 regardless of topic or content format," the study's authors report.

But if you're tempted to write clickbait headlines whose stories don't deliver the goods--don't. Keep in mind that we're looking for shares here, and not just fooling people into clicking a headline and then regretting it. You'll get nowhere unless readers find your content compelling enough to read through and pass on to their friends.

3. No surprise--Facebook dominates shares.

Well, of course it does. With 1.3 billion active users, there are so many more people on Facebook than any other social platform that it can't help but have many more shares than the others. Still, although Facebook has about 62 percent of the total users of the five social media platforms, it gets about 82 percent of the shares, indicating that users are either more engaged with Facebook, likelier to share content there, or both.

On the other hand, Twitter appears to be punching above its weight. Though the Pew Research Institute recently named it the smallest of the major social networks, Twitter saw four times as many shares as similarly sized LinkedIn.

4. It's tough to get huge amounts of attention.

Even among top publishers, getting a lot of attention for content can be tough slogging. Ninety-three percent of the publishers in the study averaged fewer than 5,000 shares per article. and only two, BuzzFeed and ViralNova, averaged more than 25,000 each. But those two had impressive share rankings with more than 60,000 shares on average per article.

Why? Probably because they put a lot of thought into the science of garnering shares. This analysis of Buzzfeed and Upworthy by study author Kelsey Libert provides some clues as to what they're doing right.

5. You can stop feeling guilty.

If you're like most people (including me) you're in a constant state of guilt over the many social media platforms you're ignoring. I, for instance, have a Pinterest account that I never use, even though I've written about Pinterest.

I've been feeling bad about this, but it turns out there's no need. Even for large publishers, it's tough to get significant traction on more than one platform at once. Though the study's authors set out to name the five best publishers at getting shared on multiple social media platforms at once, there weren't enough to fill up the roster. My interpretation: It's fine to limit your attention to one or two platforms.