The Floating University

If You're So Free, Why Do You Follow Others? 

The Sociological Science Behind Social Networks and Social Influence.

NICHOLAS CHRISTAKIS, Professor of Medical Sociology, Medicine, and Sociology at Harvard University

Lesson Overview

If you think you’re in complete control of your destiny or even your own actions, you’re wrong. Every choice you make, every behavior you exhibit, and even every desire you have finds its roots in the social universe. In his lecture "If You’re So Free, Why Do You Follow Others? The Sociology and Science Behind Social Networks," Nicholas Christakis explains why individual actions are inextricably linked to sociological pressures. Whether you’re absorbing altruism performed by someone you’ll never meet or deciding to jump off the Golden Gate Bridge, collective phenomena affect every aspect of your life.

Sociology explores two big ideas: Supra-individual factors, like race, geography, and genetics; and collective phenomena, qualities displayed by groups of people that aren’t present in the individual. So how can these concepts tell us how a radically individual act like suicide relates to social functions? The constancy of the phenomena will surprise you. Just as surprising is the notion that obesity spreads like a disease across social networks; Professor Christakis shows us how when you gain weight those around you are more likely to gain weight, and those around them, etc., all the way through the vast social network of which you are a part, whether you know it or not. This is the science of understanding social capital. What flows between people, and how do changes in social connections create new collective qualities in a group? By the end of the lecture Christakis has revealed a startling new way to understand the world that ranks sociology as one of the most vitally important social sciences.


  • Book (must purchase): N.A. Christakis and J.H. Fowler, Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives, New York: Little Brown, 1999. (Chapters 1–4 & 7–9)

Discussion Questions

(1.) How do you think that new kinds of ‘massive/passive’ data will change the social sciences? What are some experiments or analyses you can think of that could break new ground in sociology or disprove long-standing assumptions? 

(2.) What is the structure/agency dichotomy? Is the distinction between the two really so stark? What does it mean for the existence of free will?  

(3.) Consider the example of the slime molds as a model for how humans can gain valuable insights from the social behavior of animals. What other lessons can be learned from animal sociology? What does the behavior of the peaceful, sexually egalitarian bonobos, or the complex hive structure of certain ant colonies, to name a few examples, tell us about how we should structure human society?  

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About Nicholas Christakis

Dr. Nicholas Christakis is known for his research on the social factors that affect health, health care, and longevity. His most recent research was published in a general audience book Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives. He is Professor of Medical Sociology in the Department of Health Care Policy at Harvard Medical School; Professor of Medicine in the Department of Medicine at Harvard Medical School; and Professor in the Department of Sociology in the Harvard Faculty of Arts and Sciences.