Proceedings of the Annual Meeting of the Cognitive Science Society

Common ground is widely understood to facilitate coordination, but what happens when the shared expectation is competitive rather than cooperative? In a repeated coordination game, pairs received advice that was either cooperative or selfish with common ground manipulated by whether pairs knew they received identical advice. We found that advice type shaped the pattern of coordination: pairs with selfish advice converged toward asymmetric equilibria, while pairs with cooperative advice maintained symmetry. Common ground amplified this pattern: pairs who knew they shared selfish advice showed the steepest increase in round-level payoff asymmetry as rounds progressed. We interpret this as recursive reasoning shaping equilibrium selection: common ground on selfish advice, increases expectations of selfishness, making acceptance of asymmetry rational—anticipation reinforcing the pattern. Linguistic analysis complements this, where participants' use of "we" tracked fairness outcomes. These findings demonstrate that common ground shapes not just whether coordination succeeds, but the kind of coordination.