Effect of adaptation on the perception and production of vowel duration preceding stop consonants

Abstract

The effects of adaptation were tested: (1) on listeners’ categorization of post-vocalic stop consonants as voiced or voiceless on the basis of preceding vowel duration using short (125 ms) and long (375 ms) vowel adaptors and (2) on speakers’ production of vowel duration preceding voiced and voiceless stop consonants using short (125 ms) and long (375 ms) vowel adaptors and pseudo-adaptors including a speech noise and an /m/ sound. It was found that: (1) Listeners are able to categorize post-vocalic stops as voiceless /t/ or voiced /d/ based on the variation in the duration of the preceding vowel; (2) After listening to a repetitive stimulus of fixed long or short vowel duration, subjects shift the locus of the perceptual phonetic boundary between voiced and voiceless stops toward the value of the adapting stimulus; (3) The mean shift in phonetic boundary locus is significant in the case of the short adapting stimulus and non-significant in the case of the long adapting stimulus; (4) The measured durations of subjects’ vowels in AT utterances show a significant shift toward the adapting stimulus when it is short; and (5) The measured durations of subjects’ vowels in AD utterances do not appear to be affected by the long adapting stimulus.