Is it our nature to act in self-interest – or in ways that benefit the greater good? Are these two modes of behavior mutually exclusive – or are they complementary, linked, maybe even synonymous? These questions, wondered aloud among a group of us at last week’s Communities of Health meetings in Michigan, are brought to light in yesterday’s The New York Times Magazine cover story by Clive Thompson, “Is Happiness Catching?”
Thompson profiles the work of Nicholas Christakis and James Fowler, who say “they have for the first time found some solid basis for a potentially powerful theory in epidemiology: that good behaviors – like quitting smoking or staying slender or being happy – pass from friend to friend almost as if they were contagious viruses.” Drawing on data from the landmark Framingham Heart Study, which has followed 15,000 participants since its inception in 1948, the researchers conclude that “staying healthy isn’t just a matter of your genes and your diet” but also your “proximity to other healthy people.” This influence is true, they say, not just among close friends and family members, but also across “three degrees of influence” (e.g., your indirect connection to your son’s best friend’s mother).
“People are connected, and so their health is connected,” Christakis and Fowler concluded when they summarized their findings in a July 2007 article in The New England Journal of Medicine, the first time the prestigious journal published a study of how social networks affect health, reports Thompson.
And the social effect appeared to be quite powerful. When a Framingham resident became obese, his or her friends were 57 percent more likely to become obese, too… A Framingham resident was roughly 20 percent more likely to become obese if the friend of a friend became obese… Risk of obesity went up about 10 percent even if a friend of a friend of a friend gained weight.
A friend taking up smoking increased your chance of lighting up by 36 percent, and if you had a three-degrees-removed friend who started smoking, you were 11 percent more likely to do the same. Drinking spread socially, as did happiness and even loneliness. And in each case one’s individual influence stretched out three degrees before it faded out. They termed this the “three degrees of influence” rule about human behavior: We are tied not just to those around us, but to others in a web that stretches farther than we know.
In the case of happiness, Thompson writes, what’s most important is to have a lot of friends: “The researchers say increased sociability pays off because happiness is more contagious than unhappiness. Each new happy friend boosts your good cheer by 9 percent; each new unhappy friend drags you down by only 7 percent.”
Christakis and Fowler’s critics argue that “ascertaining cause and effect in such complex constructs” is difficult. Indeed, other mechanisms are likely at work, including the shared environment and the tendency of people to gravitate toward others who are like them. Whether or not this specific research proves the point, most do agree that within the complex array of interconnected forces – the ecology of health – human behavior is widely contagious and important. (As someone said in our CoH gatherings last week, there are certain truths we can intuit without exhaustive scientific studies, like the fact that driving with a blindfold on at 100 MPH is more likely to result in a car crash.)
This suggests new ways of thinking about population health improvement, giving due to the power context over individual behavior: “If they’re right,” notes Thompson, “initiatives that merely address the affected individuals are doomed to failure.” For example, rather than dieting alone or with your immediate friends, Christakis and Fowler suggest that dieting with friends of friends – across multiple degrees of influence – could create a “counterepidemic of skinniness.” In fact, using simulation models that measure the impact of healthy behaviors across extended social networks, the researchers demonstrated that obesity trends could be reversed.
Just as interesting and relevant to our CoH work is Christakis and Fowler’s observation that social contagion could even help explain the evolutionary imperative of altruism. Writes Thompson:
Tribal groups that were tightly connected were likely more able to pass along positive behaviors than those that weren’t… If we can pass on altruism to distant points in a network, it would help explain why altruistic people aren’t simply constantly taken advantage of by other members of their community. Last year, to test this theory, they conducted a laboratory experiment in which participants played a “cooperation game.” Each participant was asked to share a sum of money with a small group and could choose to be either generous or selfish. Christakis and Fowler found that if someone was on the receiving end of a generous exchange, that person would become more generous to the next set of partners – until the entire larger group was infected, as it were, with altruistic behavior, which meant the altruist would benefit indirectly.
As Fowler pointed out, if you want to improve the world with your good behavior, math is on your side. For most of us, within three degrees we are connected to more than 1,000 people – all of whom we can theoretically help make healthier, fitter and happier just by our contagious example. “If someone tells you that you can influence 1,000 people,” Fowler said, “it changes your way of seeing the world.”
So, whether this is science or intuition (or both), it is increasingly a “truth” we are hearing again and again in CoH gatherings all over the country. And in this, we no longer see a separation between self-interest and the greater good. In this, we see that our hope and our health are inextricably linked to us all.