Four years ago, researchers reported in the New England Journal of Medicine that obesity could be contagious, like a virus or a Lady Gaga video. I took the finding to heart, and immediately unfriended everyone on Facebook with a body-mass index over 25, just in case it was contagious through social media, too. (Gaga made the cut.)
Now I find that, perhaps, I was too quick to turn on my Facebook friends, who are probably friends no longer. In an interesting piece on Slate, David Johns writes that the idea of social contagion–which also includes a claim that divorce can spread through personal networks–is not as solidly established as we might have thought.
Johns says some researchers now question how social contagion got past peer review in the New England Journal. And some have gone further, examining the evidence and finding holes.
The research in question was done by James H. Fowler of the University of California, San Diego, and Nicholas Christakis of Harvard, and their colleagues. In the New England Journal article, they examined data from the famous Framingham Heart Study, which tracked residents of a small town not far from Boston for decades. The data included the body-mass index (a measure of obesity) for the study’s participants. Fowler and Christakis looked at whether “weight gain in one person was associated with weight gain in his or her friends, siblings, spouse, and neighbors.” They concluded that “obesity appears to spread through social ties.”
In a nice turn of phrase, Johns writes, “It’s a surprising, quirky, and seemingly plausible finding, which explains why so many news outlets caught the bug.” He’s right about that: A finding that is both surprising and plausible is sure to attract attention. Anybody could see that this was almost surely right.
But, of course, science doesn’t always work that way. Often that which seems to be highly implausible is what turns out to be right (light is both a particle and a wave).
Last year, Fowler and Christakis followed up with another paper, entitled Breaking Up is Hard To Do, Unless Everyone Else is Doing it Too, in which they concluded “that divorce can spread between friends, siblings, and coworkers.”
Johns notes an earlier piece of his in Slate in which he reported on a study that challenged the statistics used by Fowler and Christakis, charging that they were in error. Johns takes a shot at Fowler and Christakis for promoting their work in popular venues, including on the Stephen Colbert show and in TED videos, which is a little unfair; the argument turns on the strength of the data here, not the publicity.
But Johns makes an important related point. The divorce paper has not been subject to peer review; it was posted as a preprint, and is still awaiting publication. Johns is right to argue that publicity before peer review is a risky business. Johns walks a line, being careful not to discard social contagion–but to suggest only that it’s less well established than it seems.
That’s a fair point. I went into this story a little dubious that Johns could come to a reasonable position on all of this, without coming down for or against Fowler and Christakis. They might be right; what seemed plausible before the criticism still seems plausible. But Johns tied up his story very neatly–it’s a nice job. The point is that we need to know a lot more before we start unfriending our friends.
– Paul Raeburn