Behavioral economics has had enormous success in the last several decades in making progress towards its goal of making economic theory more psychologically realistic. Through the use of careful experiments, clever modeling and convincing analysis of data, behavioral economists have developed a powerful, predictive portrait of how humans reason about and respond to risk, uncertainty, time delay and small scale social interactions. But behavioral economics thus far has not yet seriously turned its powerful lens towards the classical focus of economic theory: understanding how individuals respond to and reason about the mass behavior of large groups of people. Yet understanding the special psychology of mass behavior, and how it impacts markets, online cohorts, mass movements and electorates, has never been more urgent in our increasingly connected world. In this research, the investigator will use the powerful conceptual and empirical tools of contemporary behavioral economics to answer some basic questions about the psychology of mass behavior in order to guide the development of predictive models and guide decisions. Using experiments, the researcher will explore how large groups reason together, how individuals reason about large groups and how people respond to the strategic powerlessness of acting as a member of a large group. The dataset gathered by the investigator and the conceptual insights gleaned from it will allow us to better understand the function of hu