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Exclusion, congestion, and the evolution of collective action
By Jorge Peña (IAST, Toulouse)
February 26, 2019 at 11:00AM - Salle de séminaires 5ème étage, Tour 32-33


Collective action occurs when individuals work together to provide a collective good. Examples abound in the social and natural sciences: humans collectively build houses, roads, and walls; lions work together to catch large game; bacteria secrete enzymes that benefit other bacteria. Yet cooperation of this kind poses a collective action problem: if individual effort is costly there is an incentive to reduce or withdraw one's effort, and if enough individuals follow this logic the collective good will not be provided. Collective action problems are usually studied within the framework of (evolutionary) game theory: social interactions are modeled as games between several players, with solution concepts such as the Nash equilibria (or evolutionarily stable strategies, or stable rest points of the replicator dynamics) providing behavioral or evolutionary predictions. After a brief introduction to evolutionary game theory, I will review some of my past and present work on the analysis of collective action problems from a game-theoretic perspective. Then I will present work in progress focusing on how different types of exclusion (i.e., the extent to which certain individuals can be prevented from consuming the good, once it is produced) and congestion (i.e., the degree to which an individual's benefit is affected by the total number of consumers) affect incentives to cooperate as the size of the interacting group increases or becomes arbitrarily large. An application to strategies of symbiont acquisition by hosts in the context of mutualisms will be discussed and used to illustrate the theoretical results.