Random Strategies in a Two Levels Iterated Prisoner ’ s Dilemma : How to Avoid Conflicts ?

The Iterated Prisoner's Dilemma is a model for studying cooperation and conflicts. Some variants of it seems to lead to new interesting conclusions. The Iterated Lift Dilemma is such a variant that we will study in this paper. The following points are to be noted: (i) two levels of cooperation are now possible, the best one needs a difficult coordination between considered strategies; (ii) only proba-bilistic strategies can make a hight score when they play against themselves ; (iii) more complex dynamics can appear (the " edge of chaos " ?) as soon as three strategies are confronted. Our idea, already defended about the classical I.P.D., is that, in spite of the model simplicity you can obtain many complex phenomena: it is not true that to be good, a strategy must be simple. Building good strategies for the Iterated Lift Dilemma is then much more difficult than for the classical game.