Effects of ensemble action selection on the evolution of iterated prisoner's dilemma game strategies

Iterated prisoner's dilemma (IPD) games have been frequently used for examining the evolution of cooperative game strategies. It has been pointed out in some studies that the choice of a representation scheme (i.e., coding mechanism) has a large effect on the evolution. A choice of a different representation scheme often leads to totally different results. In those studies on IPD games, a single representation scheme is assigned to all players. That is, all players have the same representation scheme. In our former studies, we reported experimental results in an inhomogeneous setting where a different representation scheme was assigned to each player. The evolution of cooperation among different types of game strategies was examined. In this paper, we report experimental results in another interesting setting where each player is assumed to have multiple strategies with different representation schemes. The next action of each player is determined by a majority vote by its strategies. That is, each player is assumed to have an ensemble decision making system. Experimental results in such an ensemble IPD model are compared with those in the standard IPD model where each player has a single strategy.