Words refer to objects in the world, but this correspondence is not one-to-one: Each word has a range of referents that share features on some dimensions but differ on others. This property of language is called underspecification. Parts of the lexicon have characteristic patterns of underspecification; for example, artifact nouns tend to specify shape, but not color, whereas substance nouns specify material but not shape. These regularities in the lexicon enable learners to generalize new words appropriately. How does the lexicon (...) come to have these helpful regularities? We test the hypothesis that systematic backgrounding of some dimensions during learning and use causes language to gradually change, over repeated episodes of transmission, to produce a lexicon with strong patterns of underspecification across these less salient dimensions. This offers a cultural evolutionary mechanism linking individual word learning and generalization to the origin of regularities in the lexicon that help learners generalize words appropriately. (shrink)

Utterances can convey more information than they explicitly encode, and speakers exploit communicative conventions in order to say more with less. However, the burden this places on perceivers is not well understood. This chapter examines the effect of speaker-specific information on pragmatic inferences using data from an experiment which investigated the time course of the use of pragmatic information in language comprehension. Previous evidence suggests that comprehenders who encounter a referential form, including a modifier that commonly indicates contrastiveness, assume that (...) the referential form is being used contrastively. Thus, they consequently look to the relevant object in the scene very early when processing the referential expression. In this case, people appear to be implicitly following H. P. Grice’s maxim of quantity. This chapter demonstrates that comprehenders stop using contrastive information early in resolving reference when speakers consistently do not use contrastive elements appropriately, consistent with a pragmatic explanation of referential contrast effects. (shrink)

We examine the problem of generating definite noun phrases that are appropriate referring expressions; that is, noun phrases that (a) successfully identify the intended referent to the hearer whilst (b) not conveying to him or her any false conversational implicatures (Grice, 1975). We review several possible computational interpretations of the conversational implicature maxims, with different computational costs, and argue that the simplest may be the best, because it seems to be closest to what human speakers do. We describe our recommended (...) algorithm in detail, along with a specification of the resources a host system must provide in order to make use of the algorithm, and an implementation used in the natural language generation component of the IDAS system. (shrink)