Existence of subgame perfect equilibrium with public randomization: A short proof

Consider a multi-stage game where each player has a compact choice set and payoffs are continuous in all such choices. Harris, Reny and Robson (1995) prove existence of a subgame perfect equilibrium as long as a public correlation device is added to each stage. They achieve this by showing that the subgame perfect equilibium path correspondence is upper hemicontinuous. The present paper gives a short proof of existence that focuses on equilibrium payoffs rather than paths.Existence

The evolution of decision and experienced utility

Psychologists report that people make choices on the basis of "decision utilities'' that routinely overestimate the "experienced utility'' consequences of these choices. This paper argues that this dichotomy between decision and experienced utilities may be the solution to an evolutionary design problem. We examine a setting in which evolution designs agents with utility functions that must mediate intertemporal choices, and in which there is an incentive to condition current utilities on the agent's previous experience. Anticipating future utility adjustments can distort intertemporal incentives, a conflict that is attenuated by separating decision and experienced utilities.Evolution, decision utility, experienced utility, focusing illusion

Efficiency in Evolutionary Games: Darwin, Nash and the Secret Handshake

This paper considers any evolutionary game possessing several evolutionarily stable strategies, or ESSs, with differing payoffs. A mutant is introduced which will "destroy" any ESS which yields a lower payoff than another. This mutant possesses a costless signal and also conditions on the presence of this signal in each opponent. The mutant then can protect itself against a population playing an inefficient ESS by matching this against these non-signalers. At the same time, the mutants can achieve the more efficient ESS against the signaling mutant population itself. This construction is illustrated by means of the simplest possible example, a co-ordination game. The one-shot prisoner's dilemma is used to illustrate how a superior outcome which is not induced by an ESS may be temporarily but not permanently attained. In the case of the repeated prisoner's dilemma, the present argument seems to render the "evolution of co-operation" ultimately inevitable.Center for Research on Economic and Social Theory, Department of Economics, University of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/100926/1/ECON374.pd