The hidden influence of social networks

“People aren’t merely social animals in the usual sense, for we don’t just live in groups. We live in networks — and we have done so ever since we emerged from the African savannah. Via intricately branching paths tracing out cascading family connections, friendship ties, and work relationships, we are interconnected to hundreds or even thousands of specific people, most of whom we do not know. We affect them and they affect us.”

Nicholas Christakis’ work examines the biological, psychological, sociological, and mathematical rules that govern how we form these social networks, and the rules that govern how they shape our lives. His work shows how phenomena as diverse as obesity, smoking, emotions, ideas, germs, and altruism can spread through our social ties, and how genes can partially underlie our creation of social ties to begin with. His work also sheds light on how we might take advantage of an understanding of social networks to make the world a better place.

At Harvard, Christakis is a Professor of Medicine, Health Care Policy, and Sociology, and he directs a diverse research group investigating social networks. His popular undergraduate course (Life and Death in the US) is podcast [available on itunes]. His book, Connected, co-authored with James H. Fowler, appeared in 2009, and has been translated into nearly 20 languages. In 2009, he was named by Time magazine to its annual list of the 100 most influential people in the world, and also byForeign Policy magazine to its list of 100 top global thinkers.

“If your friends are obese, your risk of obesity is 45 percent higher. … If your friend’s friends are obese, your risk of obesity is 25 percent higher. … If your friend’s friend’s friend, someone you probably don’t even know, is obese, your risk of obesity is 10 percent higher. It’s only when you get to your friend’s friend’s friend’s friends that there’s no longer a relationship between that person’s body size and your own body size.”

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