Why are you telling me this? The availability and timing of relevance inferences

Part of successful communication involves recognising the purpose of, or the intentions underlying, what speakers choose to say. Often, such pragmatic inferences are studied with an emphasis on informativity. The present work however moves beyond the types of inferences typically studied in prior work and instead investigates inferences from more naturalistic utterances, specifically those whose triviality may invite addressees to reason about why a speaker would have made such a discourse contribution. We present four studies (total N=777) using offline and online methods to investigate how and when listeners derive relevance inferences from trivial utterances. We manipulate speaker knowledge, speaker style, and linguistic properties of the utterances to show that, even in the absence of explicit emphasis cues, trivial utterances such as “the library walls are blue” are likely to be understood as conveying more than what is stated explicitly (e.g. that the walls used to be a different colour), and that these inferences are more likely to arise when produced by a speaker who is knowledgeable about the situation and who does not typically talk a lot. Our results suggest that comprehenders have pervasive expectations of cooperativity which, when seemingly violated by a speaker’s trivial utterance, prompt reasoning about a speaker’s motivation for speaking to determine how the communicated content is relevant. We then turn to the processing costs of computing triviality-driven inferences and find evidence that there may be a cost to deriving relevance inferences. These findings extend previous work on inferencing, which typically targets specific classes of words that give rise to inferences and demonstrates that broader, systematic inferencing that can arise when addressees reason about speaker goals even in the absence of cues to pragmatic enrichment.