Date of Award

Fall 2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Communication Sciences and Disorders

Advisor(s)

Vicki A. Reed

Abstract

The speech sound disorder, childhood apraxia of speech (CAS), has perplexed clinicians and researchers for many years. The perplexity has stemmed, in part, from questions about identifying characteristics that distinguish it from other childhood speech disorders. Given the reported vowel duration deficits cited in the speech production of children with sCAS, the research for this population is deficient in assessing the ability of these children to discriminate vowel duration differences. The present study represents an initial attempt to address duration discrimination in a systematized experimental design for a group of school-age TD children (n = 21) and a smaller group of school-age children diagnosed with sCAS (n = 11). All children were asked to judge whether pairs of non-word single syllable tokens (digital recordings of single syllable /ba/ varying in vowel duration only) were the same or different. Using an AX paradigm, children in the current study compared a stimulus (X), which varied across trials, with a constant standard (A). The standard A interval was the stimulus with the shortest vowel duration (208 ms) and the X interval was the comparison stimuli (i.e., vowel duration = 208 ms, 248 ms, 288 ms, 328 ms, 368 ms, 408 ms, 448 ms, or 488 ms). Fundamental frequency and amplitude measures were controlled to remain uniform. Assessing the ability of the TD population to detect duration differences in a specific experimental paradigm was prerequisite to addressing the ability of children with sCAS to detect duration differences in the same experimental task. The results of this preliminary investigation of discrimination of vowel duration in children with sCAS suggest that further research on duration discrimination skills is warranted in this population. As a group, children with sCAS displayed poorer performance on the vowel duration discrimination experimental task, compared to a similarly-aged TD group.

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