The Psychology of Common Knowledge: Coordination, Indirect Speech, and Self-conscious Emotions

The way humans cooperate is unparalleled in the animal kingdom, and coordination plays an important role in human cooperation. Common knowledge---an infinite recursion of shared mental states, such that A knows X, A knows that B knows X, A knows that B knows that A knows X, ad infinitum---is strategically important in facilitating coordination. Common knowledge has also played an important theoretical role in many fields, and has been invoked to explain a staggering diversity of social phenomena. However, no previous empirical work has directly explored the psychology of common knowledge.;Paper 1 demonstrates that people represent common knowledge, distinguish it from lower levels of shared knowledge (e.g., A knows that B knows X, but nothing more), and that common knowledge facilitates coordination for mutual benefits. The paper reports results from four experiments in which groups of participants interacted in coordination games, with varying levels of knowledge and payoffs. Results showed that common knowledge facilitates coordination, and thus provides an important proof of concept.;Paper 2 provides support from a large dyadic psychophysiology study for a recently proposed theory of strategic indirect speech, in which common knowledge plays a central role. Participants' affective reactions to different types of illicit propositions were consistent with predictions from the theory, as were their responses to survey questions that asked what they would tell their friends about the propositions. By supporting the strategic theory of indirect speech, these results provide indirect evidence that common knowledge plays an important role in explaining certain kinds of indirect speech.;Paper 3 provides evidence from two experiments that the self-conscious emotions of embarrassment, shame, and guilt are sensitive to the distinction between common knowledge and lower levels of shared knowledge. In the first experiment, participants read fictional scenarios that might induce these emotions, and reported that they would feel them more strongly if a transgression was common knowledge than if it was merely shared knowledge. In the second experiment, participants performed a karaoke song for a panel of judges, and reported higher levels of embarrassment when their performance was common knowledge than shared knowledge.