Articulatory compensation and adaptation for unexpected palate shape perturbation

This paper describes compensatory articulatory behavior in response to an unexpected perturbation of the oral cavity. An artificial palate, whose thickness can be changed during speech, was constructed to provide downward (increase of thickness) and upward (decrease of thickness) perturbation on the palate shape. The compensatory articulation during the utterance of repeated syllables, which contain fricative/R/and stopfricative/tR/, was recorded with an electromagnetic articulographic system. An EMG recording of tongue muscles was also made to examine the speech control mechanism of the immediate compensation of the tongue. The compensatory behavior was examined for both unmasked and masked audiofeedback conditions. The immediate compensation of the tongue to the unexpected perturbation occured within 100 ms after the perturbation for both audio-feedback conditions. It was, however, often incomplete and an overshoot of the tongue caused speech errors in the first occurrence of the fricative. The speech error disappeared and complete compensation was achieved in the successive occurrence of the phoneme during the same utterance. The time course in achieving the complete compensation was dependent on the audio-feedback condition. The masked audio-feedback condition needed a longer interval for the complete compensation.