This rule selects its choice to maximize its own longterm expected payoff on the assumption that the other rule cooperates with a fixed probability which depends only on whether the other player cooperated or defected on the previous move. These two probabilities estimates are continuously updated as the game progresses. Initially, they are both assumed to be 0.5, which amounts to the pessimistic assumption that the other player is not responsive. This rule is based on an outcome maximization interpretation of human performances proposed by Downing.