I’ve got a new essay on social networks and the research of Nicholas Christakis and James Fowler in the latest issue of Wired:
There’s something strange about watching life unfold as a social network. It’s easy to forget that every link is a human relationship and every circle a waistline. The messy melodrama of life–all the failed diets and fading friendships–becomes a sterile cartoon.
But that’s exactly the point. All that drama obscures a profound truth about human society. By studying Framingham as an interconnected network rather than a mass of individuals, Christakis and Fowler made a remarkable discovery: Obesity spread like a virus. Weight gain had a stunning infection rate. If one person became obese, the likelihood that his friend would follow suit increased by 171 percent. (This means that the network is far more predictive of obesity than the presence of genes associated with the condition.) By the time the animation is finished, the screen is full of swollen yellow beads, like blobs of fat on the surface of chicken soup.
The data exposed not only the contagious nature of obesity but the power of social networks to influence individual behavior. This effect extends over great distances–a fact revealed by tracking original subjects who moved away from Framingham. “Your friends who live far away have just as big an impact on your behavior as friends who live next door,” Fowler says. “Think about it this way: Even if you see a friend only once a year, that friend will still change your sense of what’s appropriate. And that new norm will influence what you do.” An obese sibling hundreds of miles away can cause us to eat more. The individual is a romantic myth; indeed, no man is an island.
Wired also has a series of beautiful images of the actual network data. And if you’d like to learn more about the research, I highly recommend the new book by Christakis and Fowler, Connected. And here’s a much longer article on the social network research by Clive Thompson, which does an excellent job of explaining the different ways in which the scientists try to separate causation from correlation. (Is obesity really contagious? Or did a McDonald’s just open up in the neighborhood?) It turns out that the old warning of David Hume – causation is a slippery concept and a tricky thing to prove – is even more relevant in the age of excess data, when supercomputers can sift through terabytes of social information and uncover all sorts of fallacious correlations. Christakis and Fowler get around this problem through some clever analytics: they show, for instance, that obesity is much more contagious between close friends than it is between acquaintances, which suggests that social networks are the driving mechanism (and that the new neighborhood McDonald’s isn’t). Regardless, it will be interesting to watch this new field evolve in the next few years, as the Humean skeptics do battle with the enthusiastic believers…