Sociologists have developed elaborate theories of who spreads gossip and news  who tells whom, who matters most in social networks  but they’ve had less success measuring what kind of information travels fastest. Do people prefer to spread good news or bad news? Would we rather scandalize or enlighten? Which stories do social creatures want to share, and why?

Now some answers are emerging thanks to a rich new source of data: you, Dear Reader.

Researchers at the University of Pennsylvania have intensively studied the New York Times list of most-e-mailed articles, checking it every 15 minutes for more than six months, analyzing the content of thousands of articles and controlling for factors like the placement in the paper or on the Web home page.

The results are surprising  well, to me, anyway. I would have hypothesized that there are two basic strategies for making the most-e-mailed list. One, which I’ve happily employed, is to write anything about sex. The other, which I’m still working on, is to write an article headlined: “How Your Pet’s Diet Threatens Your Marriage, and Why It’s Bush’s Fault.”

But it turns out that readers have more exalted tastes, according to the Penn researchers, Jonah Berger and Katherine A. Milkman. People preferred e-mailing articles with positive rather than negative themes, and they liked to send long articles on intellectually challenging topics.