Strategic information transmission with verifiable messages

IF THE SENDER'S PREFERENCES are monotonic in the Receiver's action, then it is known that the Sender reveals its type in every sequential equilibrium of a Sender-Receiver game with verifiable messages (see, e.g., Milgrom (1981)). Monotonicity is a natural condition in social situations such as buyer-seller relationships; but there are obviously other situations in which the ideal action for a Sender varies with its type. Accordingly, we generalize Milgrom's result by replacing monotonicity with more general conditions on the Sender's preferences, which are sufficient for existence and uniqueness of a fully revealing equilibrium in verifiable message games. These conditions include all games in which preferences satisfy the conditions which Crawford-Sobel (1982) imposed on cheap talk games.