Implicit communication in the ultimatum game

We use modified ultimatum games to examine the effect of implicit communication on behavior in bargaining. To manipulate implicit communication, we introduce random noise so that proposers cannot infer responders' decisions unless we disclose these. We find that responders reject low offers not only because they disapprove them but also because they want to demonstrate their disapproval. Proposers anticipate this effect and make higher offers to evade rejection. In a second study, proposers forward random offers rather than make their own offers. We thus exclude disapproval of the proposer's choice as a motive of rejection. Our results show that responders refrain from rejecting random offers as rejection might make them appear envious. Our study contributes to the growing literature on communication in bargaining, which has focused on explicit rather than implicit communication.