 It has often been argued that rational self-interested players can obtain the cooperative outcome by making their moves conditional on the moves of the other player. Peter Danielson, for example, favors a strategy of reciprocal cooperation: if the other player would cooperate if you cooperate and would defect if you don't, then cooperate, but otherwise defect. Conditional strategies like this are ruled out in the versions of the game described above, but they may be possible in versions that more accurately model real world situations. In this section and the next, we consider two such versions. In this section we eliminate the requirement that the two players move simultaneously. Consider the situation of a firm whose sole competitor has just lowered prices. Or suppose the buyer of a car has just paid the agreed purchase price and the seller has not yet handed over the title. We can think of these as situations in which one player has to choose to cooperate or defect after the other player has already made a similar choice. The corresponding game is an asynchronous or extended PD.