Promises and endogenous reneging costs

We present a novel mechanism that explains how nonenforceable communication about future actions has the capacity to improve efficiency. We explore a two-player partnership game where each player, before choosing a level of effort to exert on a joint project, makes a cheap talk promise to his partner about his own future effort. We allow agents to incur a psychological cost of reneging on their promises. We demonstrate a strong tendency for evolutionary processes to select agents who incur intermediate costs of reneging, and show that these costs induce second-best optimal outcomes.