Jaw movements under delayed auditory feedback.

Abstract

The spatial and temporal movement characteristics of the jaw while subjects spoke under delayed auditory feedback was investigated. An analog-digital-analog computer system was used to instrument the delayed speech signal and a strain-gauge transducer was used to monitor the movements of the jaw. The speech sample consisted of the high, middle, and low front vowels /i/, /ɛ/, and /æ/ embedded in the carrier phrase: “That's a CVC a month.” Measurements were made of maximal jaw opening distances during the vowel segment, jaw activity duration throughout the utterance, and jaw velocity during the opening and closing phases of the vowel gesture. The disruptive effects caused by the temporally delayed speech signal were found to be specific to the: (1) magnitude of the delay interval; (2) vowel context; and (3) space-time dependent variable being measured. Increased jaw-opening excursions were found, depending upon the vowel context, and a positional target overshoot was noted at the 0.3-sec delay interval, especially for the midvowel /ɛ/. The time period of active jaw articulation was considerably lengthened at the 0.1-sec delay interval, especially for the high vowel /i/. The jaw velocity measures showed increased movement rates for both opening and closing vowel gestures as a function of vowel openness.