Happiness spreads through social networks like an emotional contagion, according to a study that looked at nearly 5,000 individuals over a period of 20 years. “We’ve found that your emotional state may depend on the emotional experiences of people you don’t even know, who are two to three degrees removed from you,” says Harvard Medical School professor Nicholas Christakis, who, along with James Fowler from the University of California, San Diego co-authored this study. “And the effect isn’t just fleeting.”
When an individual becomes happy, the network effect can be measured up to three degrees. One person’s happiness triggers a chain reaction that benefits not only his friends, but his friends’ friends, and his friends’ friends’ friends. The effect lasts for up to one year. Conversely, sadness does not spread through social networks as robustly as happiness.
But the real surprise comes with indirect relationships. Again, while an individual becoming happy increases his friend’s chances, a friend of that friend experiences a nearly 10 percent chance of increased happiness, and a friend of *that* friend has a 5.6 percent increased chance—a three-degree cascade. “We’ve found that while all people are roughly six degrees separated from each other, our ability to influence others appears to stretch to only three degrees,” says Christakis. “It’s the difference between the structure and function of social networks.”
“Imagine an aerial view of a backyard party,” Fowler explains. “You’ll see people in clusters at the center, and others on the outskirts. The happiest people tend to be the ones in the center. But someone on the fringe who suddenly becomes happy, say through a particular exchange, doesn’t suddenly move into the center of the group. He simply stays where he is—only now he has a far more satisfying sense of well-being. Happiness works not by changing where you’re located in the network; it simply spreads through the network.”
These effects are limited by both time and space. The closer a friend lives to you, the stronger the emotional contagion. But as distance increases, the effect dissipates. This explains why next door neighbors have an effect, but not neighbors who live around the block. In addition, the happiness effect appears to wear off after roughly one year. “So the spread of happiness is constrained by time and geography,” observes Christakis.
Reference: Nicholas Christakis, Professor of Medical Sociology, Harvard Medical School; Professor of Sociology, Harvard Faculty of Arts and Sciences, James Fowler, Associate Professor of Political Science, University of California, San Diego; Harvard Medical School December 4, 2008