Endogenous ambiguity in cheap talk

We provide a rationale for ambiguous communication. We do so by considering a cheap talk game in which a (possibly ambiguity averse) sender (S) able to randomize according to unknown probabilities faces an ambiguity averse receiver (R). We show that under fairly general circumstances, there exist equilibria featuring Ellsbergian communication strategies that allow both S and R to obtain a higher ex ante payoff than any non-Ellsbergian equilibrium. Ambiguity allows to shift R’s response to information towards S’s favorite action. R also benefits because ambiguous equilibria involve a larger amount of information transmission.