Perceptuo-motor adaptation to speech: an analysis of bisyllabic utterances and a neural model

acoustic measurements revealed that tow other properties of the [rethi] utterances, the vowel duration of the stressed [i] and the closure gap of the voiceless plosive, did not covary...

Abstract

After repetitive listening to a voiceless plosive contained in a consonant + vowel syllable, the voice onset time (VOT) durations of a voiceless plosive uttered in a CV environment are systematically shortened. This effect, which provided initial evidence for a common processor mediating the perception and production of speech, has been extended in this large-scale study to the case of voiceless plosives embedded in a CVCV́ environment. For the utterances [rephí] and [rethí] shortening effects were observed similar to the effects found earlier for simple CV utterances [phi] and [thi]. Although [rephí] was used as the CVCV́ adapting stimulus, the average magnitude of the perceptuo-motor effect was considerably larger for [rethí] utterances than for [rephí] utterances (6.5 msec of VOT compared with 2.7 msec of VOT). Additional acoustic measurements revealed that tow other properties of the [rethí] utterances, the vowel duration of the stressed [í] and the closure gap of the voiceless plosive, did not covary with the changes in VOT that accompanied perceptuo-motor adaptation. These results suggest that the perceptuo-motor effect observed for VOT does not merely reflect changes in stress and/or speaking rate, but rather fatique within a neural mechanism that controls the perception and production of either VOT or more specific variables associated with this coverall acoustic property. A model of the neural mechanism is proposed to account for the effects observed in both perceptual and perceptuo-motor adaptation experiments. Subject Classification: 70.30, 70.20.