Abstract:

Using covariance structure anaysis, two linear models of vowel duration were tested. The first model, the Direct Effects Only model, tested the direct effects on vowel duration of intrinsic duration, following consonant voicing, stress, position in utterance, change in fundamental frequency, and final lengthening. The second model, the Direct and Indirect Effects model, tested all of the above direct effects on duration, plus the indirect effects of stress and phrase final position on vowel duration via their effects on fundamental frequency change. Model goodness of fit was estimated by three fit indices: the Normed Fit Index (NFI), the Nonnormed Fit Index (NNFI), and the Comparative Fit Index (CFI). The Direct Effects Only model yielded the following fit indices: NFI=0.810, NNFI=0.788, and CFI=0.821. The Direct and Indirect Effects model yielded slightly higher fit indices: NFI=0.822, NNFI=0.802, and CFI=0.833. Position in syllable, position in phrase, intrinsic duration, phrase final position, stress, and change in frequency were significant predictors of duration in both models. In the Direct and Indirect Effects model, phrase final position had an indirect effect on vowel duration via a significant effect on change in frequency; stress did not.