Emotional expressivity and trustworthiness: The role of nonverbal behavior in the evolution of cooperation

Previous research has found that high emotional expressivity contributes to interpersonal attraction independently of and on par with the contributions of physical attractiveness. Using an evolutionary perspective, we argue that emotional expressivity can act as a marker for cooperative behavior or trustworthiness. Theoretical and empirical work from social dilemma research pointing to the advantages of having a signal for cooperation is considered, as well as research from the limited number of studies that have looked at expressive behavior within a social exchange context. We also argue that we need to inject nonverbal emotional behavior into the social dilemma paradigm, which has downplayed or ignored its role in the communication processes associated with cooperation. Finally, we offer an outline for testing our theory and expanding the role of nonverbal emotional processes within research on cooperation and social exchange.