I bet you’ve had at least one friend or coworker who never stays at home when they’re sick. The kind who will sit next to you and cough, sneeze, and hack their way through meetings, while you and everyone around them edge slowly away or glance around furtively in search of Purel. It’s not that you don’t like that person, but you understand that being in contact with germs will turn you into the next coughing sneezer who people will avoid like…..well, the plague.
But what if I told you that colds aren’t the only thing you can catch from your neighbor? We often think of happiness as something we experience within ourselves, but it turns out that happiness is as contagious as the common cold. And over time, we spread it to those around us.
When we look at social networks, we see clusters of happy people grouped together. At first, there might seem to be a simple explanation for this – after all, people are more likely to hang out with people who are like them, and it would make sense that happy people would want to spend time together. But as we track social networks over time, we see that the tendency to be happy will spread from person to person, rather than happy people simply tending to cluster together.
When we take the same methods that epidemiologists use to track illnesses, and use them to look at long-term emotions among groups of people, it becomes clear that happiness moves infectiously around a social network very much like a disease. Happiness spreads the fastest to those whom we live in close proximity to. Having a happy friend who lives within a mile of you increases the probability that you will be happy by a sizeable 25%, and a happy next-door neighbor increases the likelihood that you’ll be happy by 34%. Although the effects of happiness will decay with time and distance between people, we’re still significantly affected by the happiness of people even three degrees of separation away from us (that is, the happiness of friends of friends of friends).
This effect is not limited to short-term moods. While a friend’s cheerful greeting may put a smile on our face for a few seconds, spending time around happy people increases our tendency to be happy over time.
I could end this note with a dour, cautionary note about choosing your friends wisely, but in the spirit of spreading happiness, why not instead look at the way we affect those around us? If our happiness can increase the happiness of even friends of friends who we haven’t actually met, then it’s worth considering what kind of emotion we are spreading around the world every day. Unlike a bad cold, don’t cover your mouth when you smile.
Fowler, J., & Christakis, N. (2008). Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years in the Framingham Heart Study BMJ, 337 (dec04 2) DOI: 10.1136/bmj.a2338
Hill, A., Rand, D., Nowak, M., & Christakis, N. (2010). Emotions as infectious diseases in a large social network: the SISa model Proceedings of the Royal Society B: Biological Sciences, 277 (1701), 3827-3835 DOI: 10.1098/rspb.2010.1217