BAD NEWS SELLS. If it bleeds, it leads. No news is good news, and good news is no news.

Those are the classic rules for the evening broadcasts and the morning papers, based partly on data (ratings and circulation) and partly on the gut instincts of producers and editors. Wars, earthquakes, plagues, floods, fires, sick children, murdered spouses — the more suffering and mayhem, the more coverage.

But now that information is being spread and monitored in different ways, researchers are discovering new rules. By scanning people’s brains and tracking their e-mails and online posts, neuroscientists and psychologists have found that good news can spread faster and farther than disasters and sob stories.

“The ‘if it bleeds’ rule works for mass media that just want you to tune in,” says Jonah Berger, a social psychologist at the University of Pennsylvania. “They want your eyeballs and don’t care how you’re feeling. But when you share a story with your friends and peers, you care a lot more how they react. You don’t want them to think of you as a Debbie Downer.”

Researchers analyzing word-of-mouth communication — e-mails, Web posts and reviews, face-to-face conversations — found that it tended to be more positive than negative, but that didn’t necessarily mean people preferred positive news. Was positive news shared more often simply because people experienced more good things than bad things?