Compensatory responses of articulators to unexpected perturbation of the palate shape

This paper describes compensatory articulatory behavior in response to an unexpected perturbation of the oral cavity. A mechanical device was used to change dynamically the thickness of an artificial palate; the thickness of the un-inflated artificial palate was increased or the thickness of the already inflated artificial palate was decreased. The palatal perturbations were introduced under conditions of normal and masked auditory feedback. Acoustic, perceptual, and speech movement changes were examined in response to the experimental conditions. An EMA system was used to look for evidence of compensatory articulation during the utterance of repeated CV syllables containing fricative /∫/ and affricate /t∫/. When perturbation by palatal inflation was randomly given just before the initial syllable in the repeated fricative syllable, there was frequent overshoot of the tongue in forming the constriction, causing speech errors in the first syllable with the fricative. Compensation by the tongue for the unexpected palatal inflation became evident around the second syllable and the speech error disappeared in the successive syllables. Even when auditory feedback was masked, rapid compensatory articulation of the tongue was observed around the second syllable, but speech errors randomly occurred in the successive syllables. This fact suggests that tactile feedback gathered by sensing contact between tongue and inflated artificial palate is primarily used to develop the rapid compensation, and that auditory feedback is used in finely adjusting articulation with a longer time lag.