Phonetic effects of grammatical category: How category-specific prosodic phrasing and lexical frequency impact the duration of nouns and verbs

Abstract

This paper is concerned with phonetic correlates of grammatical category, specifically the finding that nouns are pronounced with greater duration than verbs in discourse. Most previous research has attributed this difference to the sentence positions that the two grammatical categories occupy and concomitant prosodic effects. Based on previous findings, we test two further effects, namely a category-specific effect on prosodic phrasing, which leads to stronger prosodic boundaries after nouns than verbs even in maximally similar syntactic contexts, and a reductive effect of lexical frequency leading to shorter durations of the more frequent word. These effects are tested in a production study investigating durational differences of twelve noun–verb homophone pairs in English in two clause-medial contexts. We find evidence for both effects: prosodic boundaries are stronger after nouns than verbs across all conditions, resulting in greater durations of nouns due to pre-boundary lengthening. Furthermore, differences in frequency result in a reduced duration of the homophone of the pair which has the greater frequency. We propose an explanation in which phonetic effects of grammatical category are caused by the interplay of sentence prosody, category-specific prosodic phrasing and lexical frequency.