Shall I Show My Emotions? The Effects of Facial Expressions in the Ultimatum Game

Over the past fifteen years, research has demonstrated the central role of interpersonal emotions in communicating intentions, goals and desires. These emotions can be conveyed through facial expressions during specific social interactions, such as in the context of coordination between economic agents, where information inferred from them can influence certain decision-making processes. We investigated whether four facial expressions (happiness, neutral, angry and disgusted) can affect decision-making in the Ultimatum Game (UG). In this economic game, one player (proposer) plays the first move and proposes how to allocate a given amount of money in an anonymous one-shot interaction. If the other player (responder) accepts the proposal, each player receives the allocated amount of money; if he/she rejects the offer, both players receive nothing. During the task, participants acted as the responder (Experiment 1) or the proposer (Experiment 2) while seeing the opponent's facial expression. For the responders, the results show that the decision was mainly driven by the fairness of the offer, with a small main effect of emotion. No interaction effect was found between emotion and offer. For the proposers, the results show that participants modulated their offers on the basis of the responders' expressed emotions. The most generous/fair offers were proposed to happy responders. Less generous/fair offers were proposed to neutral responders. Finally, the least generous/fair offers were proposed to angry and disgusted responders.