verage of the temptation payoff and the suckers payoff (see, e.g. Rapoport and Chammah. 1965; Axelrod, 1984), in which case we have 02 > b c )2- bc +(b c ) 2 (- (- > bc. (28) 2 In what follows, it will be important to know which is the second- largest non-unit eigenvalue, especially in the c