Abstract
Research in competitive games has exclusively focused on how opponent models are developed through previous outcomes, and how peoples' decisions relate to normative predictions. Little is known about how rapid impressions of opponents operate and influence behavior in competitive economic situations, although such rapid impressions have been shown to influence cooperative decision-making. This study investigates whether an opponent's face influences players' wagering decisions in a zero-sum game with hidden information. Participants made risky choices in a simplified poker task while being presented opponents whose faces differentially correlated with subjective impressions of trust. If people use information about an opponent's face, it predicts they should systematically adjust their wagering decisions, despite the fact that they receive no feedback about outcomes, and the value associated with the gambles is identical between conditions. Conversely, if people only use outcome-based information in competitive games, or use face information inconsistently, then there should be no reliable differences in wagering decisions between the groups. Surprisingly, we find that threatening face information has little influence on wagering behavior, but faces relaying positive emotional characteristics impacts peoples' decisions. Thus, playing against opponents whose faces rank high on subjective impressions of trustworthiness leads to increased loss aversion and suboptimal wagering behavior. According to these results, the best ‘poker face’ for bluffing may not be a neutral face, but rather, a face that contains emotional correlates of trustworthiness. Moreover, it suggests that rapid impressions of an opponent play an important role in competitive games, especially when people have little or no experience with an opponent.