"Historically, we have often thought that having a small cluster of tight, long-term friends is crucial to being happy. But Christakis and Fowler found that the happiest people in Framingham were those who had the most connections, even if the relationships weren’t necessarily deep ones.
The reason these people were the happiest, the duo theorize, is that happiness doesn’t come only from having deep, heart-to-heart talks. It also comes from having daily exposure to many small moments of contagious happiness. When you frequently see other people smile -- at home, in the street, at your local bar -- your spirits are repeatedly affected by your mirroring of their emotional state. Of course, the danger of being highly connected to lots of people is that you’re at risk of encountering many people when they are in bad moods. But Christakis and Fowler say their findings show that the gamble of increased sociability pays off, for a surprising reason: Happiness is more contagious than unhappiness."
-Is Happiness Catching?-