  Speech-acts can have literal meaning as well as pragmatic meaning, but these
both involve consequences typically intended by a speaker. Speech-acts can also
have unintentional meaning, in which what is conveyed goes above and beyond
what was intended. Here, we present a Bayesian analysis of how, to a listener,
the meaning of an utterance can significantly differ from a speaker's intended
meaning. Our model emphasizes how comprehending the intentional and
unintentional meaning of speech-acts requires listeners to engage in
sophisticated model-based perspective-taking and reasoning about the history of
the state of the world, each other's actions, and each other's observations. To
test our model, we have human participants make judgments about vignettes where
speakers make utterances that could be interpreted as intentional insults or
unintentional faux pas. In elucidating the mechanics of speech-acts with
unintentional meanings, our account provides insight into how communication
both functions and malfunctions.
