Morphological effects on formant movement in spontaneous speech

Abstract

In the present study we investigate the role of morphology in the production of vowel formant movement and centralization. Our data consist of 74 monosyllabic irregular English verbs (6028 tokens) that differ between their present/past tense forms on a single vowel (e.g., sing/sang). For each vowel, we measured F1 and F2 contours and Euclidean distances from speakers’ vowel space centres (measured at the vowel midpoint). A generalized additive model of the formant trajectories and a linear mixed effects regression model of the vowel centralization distances were created comparing two morphological predictors: verb tense (past or present), and paradigmatic support for the vowel. Paradigmatic support was measured using naïve discriminative learning as a metric which determined the association strength between a vowel and tense. A strong association with the past tense is evidence for greater paradigmatic support (i.e., it is more discriminating) while a vowel strongly associated with the present tense has low support. Our results indicate that the morphological predictors have an overall effect on formant movement (both in the past tense and with low paradigmatic support) and vowel centralization. However, the morphological effects differ between individual vowels.