One of the main functions of prosodic prominence is to "highlight" the prominent word as more informative than others in an utterance. However, informativeness has been conceptualised in a number of ways in linguistics, psycholinguistics, and computational linguistics. We claim that informativeness acts on broadly two levels: information structure (focus/contrast and theme/rheme structure) and informativity (referent accessibility, predictability). We conceive both of these acting as constraints on the probabilistic alignment of words with metrical prosodic structure (Calhoun 2006). This mapping is also affected by other constraints, including syntactic constraints and constraints inherent in the production of prosodic structure itself.
In the first part of this talk, we present this theory, as well as evidence for its central predictions from a regression analysis of accenting in the Switchboard corpus (Calhoun 2008). A subset of the corpus was annotated for prosodic features, including nuclear and non-nuclear accents and phrase breaks, focus status, and lexical and syntactic features. Multiple regression models were trained to predict the accent status (nuclear, non-nuclear or unaccented) of each word, using different feature sets. Results showed that focus status was more strongly predictive of nuclear than non-nuclear accents, and vice versa for lexical features. This suggests that focus acts mainly as a constraint on the position of the nuclear accent, while the appearance of non-nuclear accents is largely determined by "low-level" factors.
In the second part of the talk, we discuss the implications of our theory for the role of prosodic structure in language production. We suggest that information structure, which affects truth-conditional and pragmatic interpretation, is part of the high-level planning of an utterance. The overall prosodic structure of the utterance, including the position of the nuclear accent, is then projected on the basis of the information structure, in the initial stages of utterance planning. Lexical predictability/accessibility, on the other hand, is strongly related to lexical retrieval. We therefore suggest that this affects low-level within-phrase prominence patterns at a much later stage of production, when words are mapped onto the word sequence. This approach makes prosodic structure a fundamental part of language production (cf. Keating & Shattuck-Hufnagel 2002).