Formal cooperation in macaque monkeys obtained via single-payoff change from formal coordination games

Coordination and cooperation are hallmarks of the behavior of social animals. Coordination requires common choices to obtain maximum benefit, whereas cooperation requires to forgo immediate selfish outcome for later common maximum benefit. A well validated economic game for investigating cooperation is Prisoner Dilemma (PD). Recent studies show that monkeys cooperate to a limited extent when playing an iterated PD. In our experiment, macaque monkeys made choices on a touchscreen to obtain juice reward whose amount depended on the choices of both animals. We designed four coordination games and two cooperation games (iterated PD) that differed only in a single payoff (the so-called temptation) while all other payoffs remained constant. The increasing temptation payoff resulted in performance that varied somewhat in the coordination game (probability of common choice between p = 0.55 and p = 0.70) but dropped in both cooperation games while nevertheless remaining significant (p = 0.28 to p = 0.68). The response time of the second player increased significantly when the first player chose the cooperative option across all games, suggesting reciprocation; further, the animals seemed to benefit from seeing the action of the other player, indicating that the choices incorporated a social component. Taken together, our results demonstrate good cooperation in the iterated PD by macaque monkeys after being primed with coordination games.