<Tr> <Td> </Td> <Td> This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2012) (Learn how and when to remove this template message) </Td> </Tr> <P> If two players play prisoner's dilemma more than once in succession and they remember previous actions of their opponent and change their strategy accordingly, the game is called iterated prisoner's dilemma . </P> <P> In addition to the general form above, the iterative version also requires that 2R> T + S, to prevent alternating cooperation and defection giving a greater reward than mutual cooperation . </P> <P> The iterated prisoner's dilemma game is fundamental to some theories of human cooperation and trust . On the assumption that the game can model transactions between two people requiring trust, cooperative behaviour in populations may be modeled by a multi-player, iterated, version of the game . It has, consequently, fascinated many scholars over the years . In 1975, Grofman and Pool estimated the count of scholarly articles devoted to it at over 2,000 . The iterated prisoner's dilemma has also been referred to as the "Peace - War game". </P>

The prisoner's' dilemma is an important game to study because