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Abstract

In game-theoretic models studying the evolution of cooperation, a common assumption is that groups are of constant size. Many natural systems, however, feature variable group sizes that are in uenced by the level of cooperation in the population. Hence, the waiting-for-volunteers dilemma, a variant of the volunteer's dilemma, proposes that individuals sequentially join a group up to the point where the critical number of cooperators required for provision of the collective good is reached. The objective of this master's thesis is to study the eect of a such group formation scheme on the evolutionary dynamics of social dilemmas in nite populations. Of focal interest are conditions for natural selection favoring cooperation and for a cooperator having a higher xation probability than a defector. A striking result is that larger population sizes impede cooperation by toughening these very conditions, whereas in the standard volunteer's dilemma with constant group size, larger population sizes promote cooperation.