PHONOLOGICAL COMPLEXITY AND SPEECH DISFLUENCY IN YOUNG CHILDREN by Kevin Anthony Eldridge B.A. Biology, Wittenberg University, 1985 M.S. Communication Sciences and Disorders, Emerson College, 1989 Submitted to the Graduate Faculty of Arts and Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2006 UNIVERSITY OF PITTSBURGH DEPARTMENT OF COMMUNICATION SCIENCE AND DISORDERS This dissertation was presented by Kevin Anthony Eldridge It was defended on April 10, 2006 and approved by Thomas Campbell, Ph.D. Christine Dollaghan, Ph.D. Kathy J. Jakielski, Ph.D. J. Scott Yaruss, Ph.D. Dissertation Director ii Copyright by Kevin Anthony Eldridge 2006 iii PHONOLOGICAL COMPLEXITY AND SPEECH DISFLUENCY IN YOUNG CHILDREN Kevin A. Eldridge, Ph.D. University of Pittsburgh, 2006 Recent theories suggest that speech disfluencies result from a disruption in the time- dependent processes of phonological and phonetic encoding (Howell & Au-Yeung, 2002; Karniol, 1995; Perkins, Kent, & Curlee, 1991; Postma & Kolk, 1993; Wingate, 1988). The purpose of this study was to examine the relationship between phonological complexity and disfluencies in the speech of preschool-age children. It was predicted that speech disfluencies would be more likely to occur in utterances with a higher degree of phonological complexity than in utterances with a lower degree of phonological complexity. Participants in this study were 12 monolingual English-speaking preschool-age children who stutter. Other than the diagnosis of stuttering, all 12 children exhibited normal speech, language, and hearing function. Each child was videotaped with a parent or guardian while engaged in a 30 minute free-play conversational interaction. Each of the participant’s utterances was examined to identify the presence of speech disfluencies. The presence of word-initial late- emerging consonants and consonant strings (LECi/CSi; Howell, Au-Yeung, & Sackin, 2000; Shriberg, 1993; Throneburg, Yairi, & Paden, 1994) and the Index of Phonetic Complexity (IPC; Jakielski, 2000) were utilized as metrics to identify a relationship between speech disfluencies and phonological complexity. Logistic regression was employed to determine the relationship between phonological complexity and disfluency for each child individually and to determine if a similar relationship existed for the group as a whole. While the results of initial analyses suggested that an utterance iv with a higher phonological complexity score was more likely to be disfluent than an utterance with a lower phonological complexity score, post-hoc analyses did not support this initial conclusion. The results of post-hoc analyses suggested that the initial results were confounded by the effect of utterance length. The best fit to the logistic regression model was achieved by utterance length (in number of words). The addition of phonological complexity did not add significantly to the regression model. The results of this study do not offer support to the contention that speech disfluency in young children is influenced by the phonological complexity of the utterance being produced (Howell et al., 2000; Weiss & Jakielski, 2001). v TABLE OF CONTENTS 1. Overview................................................................................................................................. 1 2. Literature Review.................................................................................................................. 10 2.1. Early Studies of Linguistic Complexity........................................................................ 10 2.1.1. A Note on Terminology........................................................................................ 11 2.1.2. Loci of Disfluency in Adults and Older Children................................................. 11 2.1.3. Summary of Early Studies with Adults and Older Children................................. 16 2.1.4. Loci of Disfluency in Younger Children .............................................................. 16 2.1.5. Summary of Early Studies of Linguistic Complexity and Stuttering ................... 18 2.2. Recent Studies of Phonological Complexity and Stuttering in Children...................... 19 2.2.1. A Current Model of Speech Planning and Production – WEAVER++................ 20 2.2.2. Phonological Complexity...................................................................................... 22 2.2.3. Summary of Recent Findings of Phonological Complexity in Preschool-age Speakers ................................................................................................................ 32 2.3. Statement of the Problem.............................................................................................. 34 2.3.1. Research Question ................................................................................................ 38 2.3.2. Hypothesis............................................................................................................. 38 3. Method .................................................................................................................................. 38 3.1. Participant Information ................................................................................................. 38 3.2. Data Collection ............................................................................................................. 41 3.3. Instrumentation ............................................................................................................. 42 3.4. Data Analysis Procedures ............................................................................................. 42 3.4.1. Transcription of Children’s Spontaneous Speech................................................. 42 3.4.2. Speech Fluency ..................................................................................................... 43 3.4.3. Index of Phonetic Complexity (IPC) .................................................................... 45 3.4.4. Word-initial Late-emerging Consonants (LECi) and Consonant Strings (CSi) .... 47 3.4.5. Intrajudge and Interjudge Measurement Reliability ............................................. 49 3.4.5.1. Speech Disfluencies...................................................................................... 49 3.4.5.2. Measures of Phonological Complexity......................................................... 50 3.5. Data Analysis................................................................................................................ 51 4. Results................................................................................................................................... 53 4.1. Word-initial Late-emerging Consonants and Consonant Strings Analysis .................. 53 4.1.1. Underlying Common Structure of the Participants as a Group ............................ 53 4.1.2. Relationship of Individual Participants to One Another....................................... 55 4.1.3. Summary of U-LECi/CSi Logistic Regression Analysis ...................................... 56 4.2. Index of Phonetic Complexity Analysis ....................................................................... 58 4.2.1. Underlying Common Structure of the Participants as a Group ............................ 58 4.2.2. Relationship of Individual Participants to One Another....................................... 59 4.2.3. Summary of U-IPC Logistic Regression Analysis ............................................... 60 4.3. Post-hoc Analysis to Test the Assumption of Independence for Logistic Regression . 62 4.4. Post-hoc Analysis of Adult Target Versus Actual Production ..................................... 63 4.4.1. Intrajudge Measurement Reliability for Phonological Complexity Scores of the Children’s Actual Production. .............................................................................. 63 vi 4.4.2. Correlation Between Phonological Complexity Score for Transcriptions Utilizing the Adult Target and the Children’s Actual Production Data............................... 64 4.5. Post-hoc Analysis of the Effect of Length.................................................................... 66 4.5.1. Correlations Between Utterance Length and Phonological Complexity .............. 66 4.5.2. Analyses Controlling for Utterance Length.......................................................... 67 4.5.2.1. Logistic Regression Analyses for Length-adjusted Phonological Complexity ....................................................................................................................... 67 4.5.2.2. Logistic Regression Analysis for Utterance Length in Words ..................... 68 4.5.2.3. Logistic Regression Analyses for Utterance Length with Phonological Complexity as an Additional Covariate........................................................ 72 4.5.2.4. Fluent and Disfluent Utterances Matched for Length in Number of Words 74 4.5.3. Phonological Complexity of Fluent Versus Disfluent Words .............................. 76 5. Chapter 5: Discussion ........................................................................................................... 78 5.1. Summary of Findings.................................................................................................... 80 5.2. Transcription of Child Target Versus Actual Production............................................. 81 5.3. Position of Phonologically Difficult Sounds ...............................................................