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Vowels and Consonants: The Relative Effect of Speech Sound Errors on Intelligibility Open Access


Other title
Speech Sound Disorders
Error Patterns
Phonological Disorders
Type of item
Degree grantor
University of Alberta
Author or creator
Mackie, Kaitlin M.
Supervisor and department
Pollock, Karen (Communication Sciences and Disorders)
Examining committee member and department
Boliek, Carol A. (Communication Sciences and Disorders)
McFarlane, Lu-Anne (Communication Sciences and Disorders)
Tucker, Benjamin V. (Linguistics)
Department of Communication Sciences and Disorders
Speech-Language Pathology
Date accepted
Graduation date
Master of Science
Degree level
Although speech-language pathologists (SLPs) have access to a wealth of information to guide the selection and prioritization of targets for intervention with children who have speech sound disorders (SSDs), empirical evidence needed to support such decisions is lacking. The role of vowels is often neglected in the literature (Davis & MacNeilage, 1990; Pollock & Keiser, 1990) and yet, an understanding of vowels may help to recognize the full picture of intelligibility for children with SSDs. The present study is a partial replication of an unpublished investigation by Vaughn and Pollock (1997). The present study aims to determine if: i) there is a significant difference between the effect of vowel and consonant error patterns on intelligibility; ii) there is a significant difference between individual error patterns on intelligibility regardless of vowel or consonant status. The present study differs from the previous unpublished study in that the target items were controlled for frequency and phonological density. Furthermore, speech production of words were recorded from a child’s speech rather than using computer generated speech. Participants in the present study listened to the recordings of a child saying real English words with and without specific vowel and consonant errors. Adult listeners were asked to type out the real English word that they believed the child was trying to say. Percent accuracy for each of the error categories (i.e. correct, vowel errors, consonant errors, and combined errors) or individual error patterns (e.g., Tensing, Stopping) was used as a measure of intelligibility. Analysis showed no significant differences between vowel and consonant error categories. Only one of the individual error patterns, Prevocalic Voicing, was significantly different from the 5 other error patterns. Post-hoc analysis of the joint effect of word position and individual error pattern suggested that different error patterns may affect intelligibility uniquely as a function of distinctive word positions. These data provide the evidence-based support needed to encourage clinicians to investigate vowel errors more closely and consider selecting them as targets in the remediation of SSDs.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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