 In figure 5, the payoffs are assumed to satisfy the ordering \(T \gt R \gt P \gt S\) and \(\frac{T + S}2 \lt R\). The latter requirement, although often omitted in discussions of the Prisoner’s Dilemma, ensures that in the context of an indefinitely repeated game there is no net overall advantage in the players alternating between Cooperate-Defect and Defect-Cooperate.