If I had titled this post “Cuddly Panda Tries To Recover From Penis Injury,” it would have had a much better chance of going viral. For a couple thousand years–and never more than now during the Internet Age–philosophers and scientists have wondered why certain content is spread from person to person. Why is some information more likely to connect us, even if it’s not the most vital to our safety and survival? The answer does not flatter us. From Maria Konnikova at the New Yorker blog:

“In 350 B.C., Aristotle was already wondering what could make content—in his case, a speech—persuasive and memorable, so that its ideas would pass from person to person. The answer, he argued, was three principles: ethos, pathos, and logos. Content should have an ethical appeal, an emotional appeal, or a logical appeal. A rhetorician strong on all three was likely to leave behind a persuaded audience. Replace rhetorician with online content creator, and Aristotle’s insights seem entirely modern. Ethics, emotion, logic—it’s credible and worthy, it appeals to me, it makes sense. If you look at the last few links you shared on your Facebook page or Twitter stream, or the last article you e-mailed or recommended to a friend, chances are good that they’ll fit into those categories.

Aristotle’s diagnosis was broad, and tweets, of course, differ from Greek oratory. So Berger, who is now a professor of marketing at the University of Pennsylvania’s Wharton School, worked with another Penn professor, Katherine Milkman, to put his interest in content-sharing to an empirical test. Together, they analyzed just under seven thousand articles that had appeared in the Times in 2008, between August 30th and November 30th, to try to determine what distinguished pieces that made the most-emailed list. After controlling for online and print placement, timing, author popularity, author gender, length, and complexity, Berger and Milkman found that two features predictably determined an article’s success: how positive its message was and how much it excited its reader. Articles that evoked some emotion did better than those that evoked none—an article with the headline ‘BABY POLAR BEAR’S FEEDER DIES’ did better than ‘TEAMS PREPARE FOR THE COURTSHIP OF LEBRON JAMES.’ But happy emotions (‘WIDE-EYED NEW ARRIVALS FALLING IN LOVE WITH THE CITY’) outperformed sad ones (‘WEB RUMORS TIED TO KOREAN ACTRESS’S SUICIDE’).

Just how arousing each emotion was also made a difference.”