Human and macaque pairs coordinate differently in a dyadic decision game with face-to-face action visibility

Abstract

Interactions of group-living primates with conspecifics range from cooperation to competition. Game theory allows testing the strategies that underlie such interactions, but in classical theory, agents act simultaneously or sequentially. Many real-world decisions, however, are made while directly observing partner’s actions. To investigate social decision-making under conditions of face-to-face action visibility, we developed a setup where two agents observe each other and reach to targets on a shared transparent display, enabling naturalistic interactions we call “transparent games”. Here we compared human and macaque pairs in the transparent version of the coordination game “Bach or Stravinsky”, which rewards coordination but entails the conflict about which of the two individually-preferred coordinated options to choose. Most human pairs developed coordinated behavior, and 53% adopted dynamic coordination via turn-taking to equalize the payoffs. All macaque pairs also converged on coordination, but in a simpler, static way: persistently selecting one of the two coordinated options or one of the two display sides. Two animals that underwent training with a turn-taking human confederate learned to coordinate dynamically. When tested as a pair, they mostly converged on the faster monkey’s preferred option, and a dynamic coordination emerged as animals spontaneously took turns in leading to their respective preferred option and following to the other’s. The observed choices were captured by modeling a probability to see the other’s action before own movement. Importantly, such competitive turn-taking was unlike the benevolent turn-taking in humans, who equally often initiated switches to and from their preferred option. Our findings demonstrate that dynamic coordination is not restricted to humans – although it serves a selfish motivation in macaques – and emphasize the importance of action visibility in the emergence and maintenance of coordination.