Date of Degree

2-2020

Document Type

Dissertation

Degree Name

Ph.D.

Program

Speech-Language-Hearing Sciences

Advisor

Douglas H. Whalen

Committee Members

Mark K. Tiede

Pascal van Lieshout

Mira Goral

Suzanne E. Boyce

Subject Categories

Speech and Hearing Science

Keywords

speech, motor, tongue, aging, speech errors

Abstract

This dissertation investigates three main issues in speech motor control, all of which are explored through the lens of speech error production. The speech error elicitation task used is the alternating onset, identical coda (e.g. ‘top cop’) paradigm, which in this incarnation is executed in time to a rate-increasing metronome. The first experimental chapter asks why some speakers may be more prone to the production of speech errors than others, from an individual differences perspective. A number of speaker attributes are taken into account, including age (older and younger adults), performance on a subset of cognitive tasks, as well as sensory measures such as vision and hearing. Statistical analysis indicates that forward digit span, a simple working memory task involving retaining and sequencing digit information, had the strongest relationship with propensity to make speech errors of the variables tested. Age was not a significant variable in any analyses. The second experimental chapter reports a transcription-based analysis of the acoustic data produced in the error elicitation paradigm, indicating error patterns and accommodation strategies that are salient to the perceptual system. The third chapter analyses ultrasound images of the tongue extracted from a subset of the same speech error data. Methods designed to analyze differences in the shape of the tongue during errorful and non-errorful utterances were applied. Results show that the nature of the errors produced by speakers vary along a continuum, whereby some errors look statistically similar to non-errors in shape, but others are produced in a gradient manner, exhibiting a reduced version of the shape or intrusions of gestures from other parts of the utterance. Similarly to previous studies, when the articulatory data is compared to the acoustic data, it is evident that not all errors in the articulatory data are audible and that the distribution of errors among phonemes is different when viewed from an articulatory versus an acoustic perspective.

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