Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


College of Humanities and Social Sciences


Communication Sciences and Disorders

Thesis Sponsor/Dissertation Chair/Project Chair

Elaine Hitchcock

Committee Member

Kathryn Herr

Committee Member

Michael Boyle

Committee Member

Tara McAllister


Childhood apraxia of speech (CAS) is a complex neurological speech sound disorder (SSD), involving impaired speech motor planning and programming. Speech characteristics of CAS include difficulty in sequencing motor speech movements in the absence of muscle weakness resulting in segmental (e.g., vowel/consonant distortions) and suprasegmental (e.g., inappropriate lexical stress) speech deficits. Acoustic analysis offers a robust objective diagnostic measurement of CAS for lexical stress and consonant accuracy/consistency. However, other reported CAS features, such as vowel errors and distortions, have yet to be extensively validated using acoustic analyses. This study will acoustically analyze vowel inconsistencies for corner vowels (/i, u, æ, ɑ) in older children with CAS (aged 8;0 to 15;11) compared to peers with residual speech sound disorder (RSSD) and typical development (TD). Vowel space measures (e.g., vowel space area and formant centralization ratio) and consistency (e.g., vowel cluster distribution) from 24 children (CAS=4, SSD=10, TD=10) will be assessed across variable phonetic contexts (e.g., syllable sequencing between anterior to posterior voiced/voiceless stops of increasing syllable length). children with CAS will demonstrate (1) greater vowel inconsistencies as context complexity increases and (2) a neutralized vowel space based on the corner vowels relative to children with SSD and TD.

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