Homophily, Contagion, Confounding: Pick Any Three

Cosma Shalizi, Statistics Department - Carnegie Mellon University
Individuals near each other in a social network tend to behave similarly; you can predict what one of them will do from what their neighbors do. Is this because they are influenced by their neighbors ("contagion"), or because social ties tend to form between people who are already similar ("homophily"), and so act alike, or some of both? We show that observational data can hardly ever answer this question, unless accompanied by very strong assumptions, like measuring everything that leads people to form social ties. Most observational studies therefore provide no evidence at all about the existence or strength of contagion effects. We also suggest some possible constructive responses to these results.
April, 2 2013 | 12:30 - 2:00 | 329 Soc/Psych Building

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