On September 22, 2006, PED Seminar Series Presents

Irrationality in animal communication

by Stefano Ghirlanda, PhD

In studies of both animal and human behavior, game theory is used as a tool for understanding strategies that appear in interactions between individuals. Game theory focuses on adaptive behavior, which can be attained only at evolutionary equilibrium. I will argue that behavior appearing during interactions is often outside the scope of such analysis. In many types of interaction, conflicts of interest exist between players, fuelling the evolution of manipulative strategies. Such strategies evolve out of equilibrium, commonly appearing as spectacular morphology or behavior with obscure meaning, to which other players may react in non-adaptive, irrational ways. I present a simple model to show some limitations of the game-theory approach, and outline the conditions in which evolutionary equilibria cannot be maintained. Evidence from studies of biological interactions seems to support the view that behavior is often not at equilibrium. This also appears to be the case for many human cultural traits, which can spread rapidly while having a negative influence on reproduction. The theoretical analysis of these issues is still in its infancy.

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