Yawn. Just seeing that word made you more likely to open your mouth in a big inhalation, contort your face and stretch out your arms. In other words, yawning is a contagious experience.
Now it turns out that happiness is like a yawn: it easily spreads between people in social networks. Nicholas Christakis, a doctor/sociologist at Harvard, is doing some of the most interesting work on social networks – he’s shown, for instance, that when a loved one gets ill people suffer serious medical consequences, and that the ability to quit smoking depends in large part on the number of smokers in your social circle – and his new paper looks at how happiness ripples through even remote human interactions.
While there are many determinants of happiness, whether an individual is happy also depends on whether others in the individual’s social network are happy. Happy people tend to be located in the centre of their local social networks and in large clusters of other happy people.
The happiness of an individual is associated with the happiness of people up to three degrees removed in the social network. Happiness, in other words, is not merely a function of individual experience or individual choice but is also a property of groups of people.
Indeed, changes in individual happiness can ripple through social networks and generate large scale structure in the network, giving rise to clusters of happy and unhappy individuals. These results are even more remarkable considering that happiness requires close physical proximity to spread and that the effect decays over time.
Our results are consistent with previous work on the evolutionary basis of human emotions and with work focusing on the fleeting direct spread of emotions. In addition to their internal and psychological relevance, emotions have a specifically social role: when humans experience emotions, they tend to show them. Like laughter and smiling, the emotion of happiness might serve the evolutionarily adaptive purpose of enhancing social bonds.