Robust Communication Between Parties with Nearly Independent Preferences

Abstract

We study finite-state communication games in which the sender's preference is perturbed by random private idiosyncrasies. Persuasion is generically impossible within the class of statistically independent sender/receiver preferences -- contrary to prior research establishing persuasive equilibria when the sender's preference is precisely transparent. Nevertheless, robust persuasion may occur when the sender's preference is only slightly state-dependent/idiosyncratic. This requires approximating an `acyclic' equilibrium of the transparent preference game, generically implying that this equilibrium is also `connected' -- a generalization of partial-pooling equilibria. It is then necessary and sufficient that the sender's preference satisfy a monotonicity condition relative to the approximated equilibrium. If the sender's preference further satisfies a `semi-local' version of increasing differences, then this analysis extends to sender preferences that rank pure actions (but not mixed actions) according to a state-independent order. We apply these techniques to study (1) how ethical considerations, such as empathy for the receiver, may improve or impede comm