When vague sentences inform: A model of assertability

A speaker often decides whether or not to say something based on his assess ment of the impact it would have on his hearer's beliefs. If he thinks it w ould bring them more in line with the truth, he says it; otherwise he does not. In this paper, I develop a model of these judgments, focusing specific ally on those of vague sentences. Under the simplifying assumption that an utterance only conveys a speaker's applicability judgments, I present a Bay esian model of an utterance's impact on a hearer's beliefs. From this model I derive a model of a speaker's judgment of whether or not an utterance wo uld be informative. I illustrate it with several examples of judgments of v ague and non-vague sentences. For instance, I show that it models the commo n judgment that asserting either "George is tall" or "George is not tall" w ould be misleading if George were borderline tall, but asserting "George is tall and he isn't tall" would not be.