A lecture by Harvard Professor Nicholas Christakis on face-to-face social networks, what they mean to our lives, and how they effect us. Our social networks have the power to spread obesity — or happiness — like contagion.
If you're friends are obese you have about a 45% higher likelihood of being obese yourself. If your friends' friends are obese you've got about a 25 % higher likelihood. If your friends' friends' friends are obese you have about a 10% higher likelihood. And it's only when we get to your friends' friends' friends' friends at 4 degrees of separation that there is no longer a relationship between that persons body size and yours. … this observation holds for lots of other traits, not just obesity.
Want to learn more? Read Christakis' book Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives — How Your Friends' Friends' Friends Affect Everything You Feel, Think, and Do