The Persistent Power of Promises∗

A large literature has documented the positive effect of pre-play communication on cooperation, trust, and trustworthiness. However, previous contributions focus on unrealistic settings in which senders are forced to choose their actions immediately after communicating with recipients. Using a hybrid lab and online experiment this paper provides the first evidence for the persistent power of communication. Even when 3 weeks pass between communication and actual choices, communication raises cooperation, trust, and trustworthiness by about 50%. Our results show that the previous body of short-duration laboratory experiments on trust and promises likely translates to longer-term interactions. Thus, in real-world situations, lags between the beginning of the interaction and the time to respond may not substantially alter the trustworthiness of the responder.