The phenomenon of social influence—that information, ideas, and even behaviors can spread through networks of people the way that infectious diseases do—is both intuitively appealing and potentially powerful. Yet as recent debates in the academic community have highlighted, influence is surprisingly hard to identify empirically. And even when social influence is indisputably present, it doesn’t necessarily spread in anything like the way that infectious diseases do. In this talk, I summarize the results of several projects, including an experimental study of a virtual cultural market, two observational studies of online diffusion, and two networked experiments on cooperation, that in different ways explore the relationship between individual influence and collective behavior.
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