Questioning “Social Contagion”

110630_SCI_christakis_fowlerTN Dave Johns in Slate:

Have you heard that divorce is contagious? A lot of people have. Last summer a study claiming to show that break-ups can propagate from friend to friend to friend like a marriage-eating bacillus spread across the news agar from CNN to CBS to ABC with predictable speed. “Think of this 'idea' of getting divorced, this 'option' of getting divorced like a virus, because it spreads more or less the same way,” explained University of California-San Diego professor James Fowler to the folks at Good Morning America.

It's a surprising, quirky, and seemingly plausible finding, which explains why so many news outlets caught the bug. But one weird thing about the media outbreak was that the study on which it was based had never been published in a scientific journal. The paper had been posted to the Social Science Research Network web site, a sort of academic way station for working papers whose tagline is “Tomorrow's Research Today.” But tomorrow had not yet come for the contagious divorce study: It had never actually passed peer review, and still hasn't. “It is under review,” Fowler explained last week in an email. He co-authored the paper with his long-time collaborator, Harvard's Nicholas Christakis, and lead author Rose McDermott.

A few months before the contagious divorce story broke, Slate ran an article I'd written based on a related, but also unpublished, scientific paper. The mathematician Russell Lyons had posted a dense treatise on his website suggesting that the methods employed by Christakis and Fowler in their social network studies were riddled with statistical errors at many levels. The authors were claiming—in the New England Journal of Medicine, in a popular book, in TED talks, in snappy PR videos—that everything from obesity to loneliness to poor sleep could spread from person to person to person like a case of the galloping crud. But according to Lyons and several other experts, their arguments were shaky at best. “It's not clear that the social contagionists have enough evidence to be telling people that they owe it to their social network to lose weight,” I wrote last April. As for the theory that obesity and divorce and happiness contagions radiate from human beings through three degrees of friendship, I concluded “perhaps it's best to flock away for now.”