In game theory, any game in which the players' preferences among the outcomes are partly coincident and partly opposed, motivating the players both to cooperate and to compete, as in the Prisoner's Dilemma game. A player in a mixed-motive game has to contend with an intrapersonal, psychological conflict arising from this clash of motives in addition to the interpersonal conflict of the game. At an abstract level, a mixed-motive game can be distinguished from a zero-sum game by the fact that the sum of the payoffs differs from one outcome to another, so that it is not the case that what one player gains the other(s) must necessarily lose. Mixed-motive games are therefore sometimes called variable-sum or non-zero-sum games. Compare zero-sum game.