Lying about what you know or about what you do?

We compare communication about private information to communication about actions in a one-shot 2-person public good game with private information. The informed player, who knows the exact return from contributing and whose contribution is unobserved, can send a message about the return or her contribution. Theoretically, messages can elicit the uninformed player’s contribution, and allow the informed player to free-ride. The exact language used is not expected to matter. Experimentally, however, we find that free-ride depends on the language: the informed player free-rides less—and thereby lies less frequently—when she talks about her contribution than when she talks about the return. Further experimental evidence indicates that it is the promise component in messages about the contribution that leads to less free-ride and less lying.