Learning Dynamics in Economic Games

When playing games human decision behaviour is often found to be diverse. For instance, in repeated prisoner dilemma games humans exhibit broad distributions of cooperativity and on average do not optimize their mean payoff. Deviations from optimal behaviour have been attributed to auxiliary causes including randomness of decisions, mis-estimations of probabilities, accessory objectives, or emotional biases. Here we show that also the dynamics resulting from of a general tendency to shift preferences towards previously rewarding choices in interaction with the strategy of the opponent can contribute substantially to observed lacks of ’rationality’. As a representative example we investigate the dynamics of choice preferences in prisoner dilemma games with opponents exhibiting different degrees of extortion and generosity. We find that already a very simple model for human learning can account for a surprisingly wide range of human decision behaviours. In particular, the theory can reproduce reduced cooperation against extortionists, large degrees of cooperation in generous games, as well as explain the broad distributions of individual choice rates in ensembles of players. We conclude that important aspects of the alleged irrationality of human behaviours could be rooted in the dynamics of elementary learning mechanisms.