Proceedings of the Annual Meeting of the Cognitive Science Society

Possibility and probability expressions, like possibly or prob-ably, are frequently assumed to communicate that the proba-bility of a proposition is above a certain threshold. Most pre-vious empirical research on these expressions has focused oncases of known objective chance: if the true objective proba-bility is given, would a speaker use possibly, probably or oneof their kin? Here, we investigate the use of probability expres-sions when speakers have subjective uncertainty about objec-tive chance, i.e., higher-order uncertainty. Experimental datasuggest that speakers’ choices of a probability expression is acomplex function of their state of higher-order uncertainty. Weformulate a computational probabilistic model of pragmaticspeaker behavior that explains the experimental data.