The Spread of Goodness

In recent years, it's become clear that much of our individual behavior depends on the dynamics of our social network. It doesn't matter if we're talking about obesity or happiness: they all flow through other people, like a virus or a meme. Last year, I profiled James Fowler and Nicholas Christakis in Wired, who have conducted several fascinating studies that demonstrate the power of social networks:

There's something strange about watching life unfold as a social network. It's easy to...