The power of words: A model of honesty and fairness

► We develop a game-theoretical model of honesty and fairness. ► Players suffer a utility cost if they unilaterally break norms of honesty/fairness. ► We study how communication affects cooperation in social dilemmas. ► The model predicts an increase in cooperation if pre-play talk is available. ► The increase depends on details of the communication protocol or the action stage.