Perceptual constancy of vowels in rapid speech

In three experiments, we investigated the role of extrasyllabic speech context in the identification of /t/-vowel-/t/ syllables spoken at normal and rapid rates of articulation. Syllables spoken at the normal rate were identified with at least 95% accuracy regardless of the context in which they were presented. However, in experiment I, intrinsically long vowels in rapidly articulated syllables were identified with greater accuracy when the syllables were presented in rapid-rate sentence context than when they were presented in isolation or in normal-rate sentence context. Experiment II revealed that part of the performance deficit for excised isolated rapid syllables was attributable to sequential order effects among test items, and to listeners' assumptions about whether the test syllables were or were not produced in isolation. In experiment III, test syllables were presented in the context of extracted portions of the rapid carrier sentences to determine the locus of the extrasyllabic information for vowel identity. The presence of the stressed syllable which immediately followed the test syllables in the carrier sentence was especially important for accurate identification of intrinsically long vowels in rapidly articulated syllables. Results are discussed in terms of intrinsic timing theories of speech production.