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. 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. Perhaps most of all, readers wanted to share articles that inspired awe, an emotion that the researchers investigated after noticing how many science articles made the list. Science kept doing better than we expected," said Dr. Berger, a social psychologist and a professor of marketing at Penn's Wharton School. "We anticipated that people would share articles with practical information about health or gadgets, and they did, but they also sent articles about paleontology and cosmology."

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