Joint commitment in human cooperative hunting through an 'imagined we'.

Cooperation involves the challenge of jointly selecting one from multiple goals while maintaining the team's joint commitment to it. We test joint commitment in a multi-player hunting game, combining psychophysics and computational modelling. Joint commitment is modelled through an 'imagined we' (IW) approach, where each agent infers the intention of 'we', an imagined supraindividual agent controlling all agents as its body parts. This is compared against a reward sharing model, which frames cooperation through the positive reinforcement of sharing in the rewards of a successful hunt. Both humans and IW, but not reward sharing, maintained high performance by jointly committing to a single prey, regardless of prey quantity or speed. Human observers rated all hunters in both human and IW teams as making high contributions to the catch, regardless of their proximity to the prey, suggesting that high-quality hunting stemmed from sophisticated cooperation rather than individual strategies. Unlike reward sharing hunters, IW hunters are capable of cooperating not only with one another but also with human participants actively engaged in the same hunting game. In conclusion, these results strongly suggest that humans achieve cooperation through joint commitment that enforces a single goal, rather than simply motivating members through reward sharing.