Strategic signaling or emotional sanctioning? An experimental study of ex post communication in a repeated public goods game

Several experimental studies show that ex post communication promotes generosity in situations where individual incentives contradict with common interest, like the provision of public goods. The root underlying the effect of this institution, especially in a repeated interaction, is nonetheless still obscure. This study provides a novel empirical testbed for two mechanisms by which ex post communication may affect behavior in repeated interactions : one is related to strategic signaling, the other involves emotions induces by others' opinions. The main findings are as follows. First, the presence of ex post communication (conducted through the attribution of costless disapproval points) fosters pro-social behavior and reduces free-riding. Second, I find systematic evidence that subjects tend to use ex post communication as a signaling device, whilst no evidence in favor of the emotion-based hypothesis. A possible interpretation of this phenomenon is that ex post messages are used to announce future sanctions for free-riding.