Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives

A colleague's husband's sister can make a person fat, even if they don't know her. A happy neighbor has more impact on happiness than a happy spouse. These startling revelations of how much people truly influence each other are revealed in the studies of Drs. Christakis and Fowler, which have repeatedly made front-page news nationwide. Their work shows that six degrees of separation is a notion of the past. Now, there is what Christakis and Fowler call the “Three Degrees Rule”-individuals a...