MEMORY BOOSTS COOPERATION

Abstract

The standard spatial formulation of the iterated Prisoner's Dilemma is ahistoric (memoryless): i.e., only the results generated in the last round are taken into account in deciding the next choice. Historic memory can be implemented by featuring players by a summary of their previous winnigs and choices. Here we study the effect of limited trailing memory: only the last three iterations are recorded. The effects of full and discounted memory are assessed. It is concluded that this short-type memory stimulates cooperation.