Abstract: In this project, we investigate how a listener’s awareness of a speaker’s message set affects their interpretation of the speaker’s chosen message. Participants play a prisoner’s dilemma with one-sided pre-play communication from a sender to a receiver. We assess how the receiver’s awareness of the sender’s set of possible alternative statements (including strong, weak, and empty statements) influences the receiver’s beliefs about the sender’s likelihood to cooperate and the receiver’s own likelihood to cooperate.