UBC Theses and Dissertations
Visual feedback during speech production Stelle, Elizabeth Leigh
The visual speech signal has a well-established influence on speech perception, and there is growing consensus that visual speech also influences speech production. However, relatively little is known about the response to one's own visual speech; that is, when it is presented as speech feedback. Since visual feedback is generated by the same speaking event that generates auditory and somatosensory feedback, it is temporally compatible with these typical sources of feedback; as such, it is predicted to influence speech production in comparable ways. This dissertation uses a perturbation paradigm to test the effect visual feedback has on production. Two delayed auditory feedback experiments tested the effect of different types of visual feedback on two fluency measures: utterance duration and number of speech errors. Visual feedback was predicted to enhance fluency. When the presentation of static and dynamic visual feedback was randomized within a block, utterance duration increased with dynamic visual feedback but there was no change in speech errors. Speech errors were reduced, however, when the different types of visual feedback were presented in separate blocks. This reduction was only observed when dynamic visual feedback was paired with normal auditory feedback, and for those participants who were more verbally proficient. These results suggest that consistent exposure to visual feedback may be necessary for speech enhancement, and also that the time-varying properties of visual speech are important in eliciting changes in speech production. In the bite block experiment, participants produced monosyllabic words in conditions that differed in terms of the presence or absence of visual feedback and a bite block. Acoustic vowel contrast was enhanced and acoustic vowel dispersion was reduced with visual feedback. This effect was strongest at the beginning of the vowel and tended to be stronger during productions without the bite block. For a small subset of participants the magnitude of motion of the lower face increased in response to visual feedback, once again without the bite block. The results of this dissertation provide evidence that visual feedback can enhance speech production, and highlight the multimodal nature of speech processing.
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