Evolving continuous behaviors in the Iterated Prisoner's Dilemma

Evolutionary programming experiments are conducted on a variant of the Iterated Prisoner's Dilemma. Rather than assume each player having two alternative moves in the stage-game, cooperate or defect, a continuum of possible moves are available. Players' strategies are represented by feed-forward perceptrons with a single hidden layer. The population size and the number of nodes in the hidden layer are varied across a series of experiments. The results of the simulations indicate a minimum amount of complexity is required in a player's strategy in order for cooperation to evolve. Moreover, under the evolutionary dynamics of the simulation, cooperation does not appear to be a stable outcome.