Human language is unique among the communication systems of the natural world. The vocabulary of human language is unique in being both culturally-transmitted and symbolic. In this paper I present an investigation into the factors involved in the evolution of such vocabulary systems. I investigate both the cultural evolution of vocabulary systems and the biological evolution of learning rules for vocabulary acquisition.

This paper examines a class of evolutionary models in which large shocks cause frequent movement between short-term "stable" equilibria. Mutations are rare in our model, but their eects are magnied by a "spread process" which causes a finite proportion of the population to initially adopt the entering strategy before the short-term selection dynamics takes effect. We examine the long run invariant distribution for a variety of games, under several different spread processes: most interestingly, we find that cooperative strategies prevail in the long run in the Finitely Repeated Prisoner's Dilemma game, contrary to the backward induction solution. We also study equilibrium selection in 2x2 and NxN coordination games, establishing conditions under which the risk-dominant equilibrium is selected, and demonstrate rapid convergence to the long run invariant distribution.