Phonetic Modification of Function Words

The goal of this project is to compare the contextual modifications that have been observed to affect content words (e.g. nouns, verbs, adjectives and some adverbs) vs. function words (classes of words like e.g. conjunctions, pronouns, prepositions etc., which often signal the function of a sentence’s content words). It is commonly observed that these two types of words undergo different types of phonetic modification in running speech; monosyllabic function words in particular are subject to severe reduction processes which do not seem to occur in monosyllabic content words, such as apparent loss of a final single consonant (cuppa tea), an consonant (give’em a break) or an onset consonant plus nuclear vowel (he’s done it). Extreme modifications can affect both words at a boundary between two monosyllabic function words (gonna, wanna); these examples also illustrate the reduction of the nuclear vowel to a schwa, and the fact that such pronunciation variants have been enshrined in the orthography in a way that is not common for content word variation. We use careful acoustic analysis of the type and degree of modification, combined with syntactic and prosodic labels, to distinguish among three possible accounts of these differences: 1) the Grammatical Categories hypothesis, which posits that a different set of modification mechanisms operate on function words vs. content words, 2) the Prosody hypothesis, which posits that the same set of modification mechanisms applies to both sets of words, but affects function words more severely because they often occur in prosodically weak contexts, and 3) the Frequency hypothesis, which posits that both sets of words are modified by the same mechanisms, but function words are more strongly modified because they occur with such high frequency. We have begun by assembling a quasi-complete list of the function words of American English, and are currently quantifying, for a spontaneously-spoken speech corpus that has been prosodically labelled, the pattern of loss or change in the acoustic landmarks which cue distinctive feature contrasts among words. Comparing the patterns of acoustic landmark modification in function words vs. content words in different prosodic structures will allow us to quantify and characterize the nature of the differences, and to ask whether monosyllabic content words undergo some of the same extreme phonetic variations observed in function words when they occur in similarly weak prosodic locations, and/or when they occur with very high frequency.