Articulatory and prosodic sensorimotor adaptation in speaker-listener interactions

Project Summary Altered auditory feedback is a powerful tool for studying articulatory and prosodic control and understanding how atypical speech motor control may contribute to speech and voice impairment. This tool is often used to study sensorimotor adaptation, an important speech motor learning process and a central component of theories of speech motor control. Yet a traditional altered auditory feedback paradigm involves a speaker in isolation. This method does not capture speech motor control in typical interactions in which the speaker’s goal is to convey a message to a listener. A listener can exert considerable influence over a speaker in terms of word choice and sentence structure, but the effect of the listener on motor control of articulation and prosody has not been investigated. Articulation and prosody are crucial for effective communication, yet commonly impaired in communication disorders. They also differ in important ways. For example, altering a single articulatory feature like the first vowel formant (F1) elicits a response in only that feature, but altering a single prosodic feature like fundamental frequency (fo) can elicit a response in other prosodic cues. Prosodic cues like fo, sound pressure level, and rate can be traded to reach the prosodic target, but such flexibility is less available for producing articulatory features. Given these differences in control mechanisms and target specificity for articulation and prosody, the listener may exert unequal influences on these systems. The central hypothesis of this study is that sensorimotor adaptation in both articulation and prosody will be affected by a listener, but that the listener effect will differ between these two speech subsystems. This hypothesis will be tested through two specific aims: 1) to determine the effect of the listener on sensorimotor adaptation in articulation and prosody; and 2) to compare listener effects on strength and specificity of articulatory and prosodic adaptation. Forty adults will complete sensorimotor adaptation tasks with and without a listener. Altered auditory feedback will be applied during the first word of sentences spoken during these tasks. Articulatory manipulations of F1 will shift /ɛ/ toward /ɪ/; prosodic manipulations of fo will shift emphatic stress toward neutral. A listener, when present, will respond to the speaker in a way that either confirms or contradicts the self-corrections of speech errors elicited by the altered auditory feedback. The proposed work has theoretical significance, as it will extend theories of speech motor control to ecologically valid interactions. The project has clinical significance through its potential to identify intervention targets for those with impaired self- monitoring of speech or atypical sensorimotor adaptation. It will inform interventions using external feedback to bolster an impaired self-monitoring system that may underlie articulatory and prosodic deficits.