EPENTHESIS IN CHILDREN'S CONSONANT CLUSTER PRODUCTIONS: A PERCEPTUAL AND ACOUSTICAL STUDY \ by MARTA KELCEY EVESON B.Sc, The University of Victoria, 1991 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (School of Audiology and Speech Sciences) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA April 1996 © Marta Kelcey Eveson, 1996 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Aud^nq^ qp A ^Sy^fj^V) Soe^ceS The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT The purpose of the present study was to examine epenthesis in children's consonant cluster productions from phonological and phonetic perspectives. The following questions were investigated: (1) Do consonant clusters produced with an epenthetic vowel differ in duration from those without? (2) Is the epenthetic vowel in the consonant cluster consistent in length and quality, or do co-articulatory effects occur? (3) Is the epenthetic vowel dependent in terms of duration on the phrasal context or the duration of the syllable nucleus? The subjects, S_i (Charles) and S2 (Blair), were two of six subjects in a doctoral research study investigating the application of a nonlinear phonological framework to the assessment and remediation of phonological disorders. Consonant cluster data were transcribed from the original data. Acoustic measurements included the duration of consonant clusters with and without epenthesis and the duration of the epenthetic vowel. Results of the investigation show that consonant clusters with an epenthetic vowel are significantly longer in duration than those without. No coarticulatory effects were seen between the epenthetic vowel and the syllable nucleus suggesting that the epenthetic vowel is part of the consonant cluster unit which is governed by its own timing system. Prosodically, ^syllabification of the word occurs as a result of epenthesis in the consonant cluster. The implication of these results appears to be that the consonant cluster containing the epenthetic vowel needs to be considered as a separate timing unit and representationally attributed unitary status. ii TABLE OF CONTENTS ABSTRACT II TABLE OF CONTENTS HI LIST OF TABLES VI LIST OF FIGURES VH ACKNOWLEDGEMENT VIII CHAPTER ONE INTRODUCTION 1 OVERVIEW 1 PHONOLOGY VERSUS PHONETICS 2 Phonology 3 Implications of phonological environment 4 Phonemes 4 Allophones 5 Phonetics 5 GENERAL IMPLICATIONS OF PHONOLOGICAL THEORY 6 NONLINEAR PHONOLOGY 7 Representation Versus Rules 7 Underlying Representation of Syllable Structure 8 Ffierarchical Representation of the Prosodic Tier 8 Theories of the Structure of the Prosodic Hierarchy 10 Tier Association 11 The Segmental Tier 11 Markedness 11 Developmental Implications of a Feature Hierarchy 12 CONSONANT CLUSTER DEVELOPMENT 13 Delay Versus Deviation 15 Pattern of Acquisition 16 IMPACT OF DIFFERENT METHODOLOGIES: UR VERSUS REALIZATIONS iii UNDERLYING REPRESENTATION OF CONSONANT CLUSTERS 18 TEMPORAL CO-ORDINATION IN CONSONANT CLUSTER PRODUCTION 21 COARTICULATION 22 METHODOLOGICAL IMPLICATIONS 23 TIMING CONSTRAINTS 24 Duration and Temporal Variability 25 IMPLICATIONS OF THEORETICAL MODELS 26 MODELS OF LANGUAGE PROCESSING 27 Serial Model 27 Parallel Interactive Model 28 Theoretical Assumptions 28 SUMMARY 29 CHAPTER TWO METHOD 32 SUBJECTS 32 51 Summary 33 52 Summary 34 APPARATUS AND PROCEDURES 34 MEASUREMENTS 36 Measurement Reliability 38 CHAPTER THREE RESULTS AND DISCUSSION 40 SUMMARY OF RESULTS 41 Occurrence of Epenthesis 41 Consonant Cluster Duration 42 Epenthesis as a Strategy for Overcoming Timing Demands 44 Effect of Phonological Context on the Epenthetic Vowel 44 Coarticulatory Effects 45 Epenthetic Vowel Duration 46 IMPACT OF EPENTHESIS ON PROSODIC STRUCTURE 48 Representation of Consonant Clusters 48 iv APPLICATION OF NONLINEAR PHONOLOGICAL FRAMEWORK 50 Epenthesis in a Serial Model of Language Processing 51 Epenthesis in a Parallel Interactive Model 52 STUDY LIMITATIONS 54 FUTURE RESEARCH 55 CONCLUSION 56 REFERENCES 58 APPENDIX ONE SI DATA 62 APPENDIX TWO S2 DATA 67 v LIST OF TABLES TABLE 1: Summary of Mam-Whitney test for difference in duration between consonant clusters without and with epenthesis 42 vi LIST OF FIGURES FIGURE 1: Hierarchical representation of prosodic structure 9 FIGURE 2: Alternative representation of CV syllables in onset-rime and moraic theories 10 FIGURE 3: Specified feature geometry for English 12 FIGURE 4: Representation of epenthesis and deletion processes 15 FIGURE 5: Duration of consonant clusters without and with epenthesis for Subjects 1 and 2 43 FIGURE 6: Relationship between syllable nucleus duration and epenthetic vowel duration for Subjects 1 and 2 47 FIGURE 7: Representation of epenthesis in moraic and onset-rime theories" 49 FIGURE 8: Representation of ClVeC2 as one unit 49 vii ACKNOWLEDGEMENT I would like to express my sincere gratitude to my supervisors, Dr. John H. V. Gilbert and Dr. Barbara Bernhardt, for their guidance and patience as I have made my way through this process and for the large amount of time that they have spent reading and revising numerous copies of my drafts. Thank you for the encouragement when it was needed the most. I would also like to thank my Mom and Dad for their endless support and encouragement throughout this endeavor. I could not have gotten to where I am without you. Special thanks need to go to my sister, Paige, for her statistical knowledge and help and for putting up with me during the final stages. Lastly, I would like to acknowledge the support and encouragement of all my friends and colleagues. Thanks to Eva Major for her time, resources and crisis management skills (coffee and a sense of humour) as I neared the end. Special thanks to NJG, MM, NT, ST, and CM as they were there along the way. viii CHAPTER ONE INTRODUCTION OVERVIEW When examining children's productions of initial consonant clusters it is frequently observed that correct production of clusters occurs at a late stage in phonological development. Factors such as timing and lack of neuromotor maturation contribute to a child's difficulties in combining consonants into clusters. To overcome these difficulties children use a variety of transformation processes. It has been reported (Ingram, 1976; Stoel-Gammon and Dunn, 1985) that one of these processes, epenthesis, does not occur as frequently as others (e.g. deletion of one consonant). Therefore, little attention has been paid to the effect of epenthesis on the consonant cluster unit. However, because epenthesis affects timing of the word and the cluster unit itself, it raises questions with respect to representation and syllable structure. This paper will focus on epenthesis in consonant cluster development from phonological and phonetic perspectives. To do this, it is necessary to discuss current theories of consonant cluster representation in the underlying phonology and to examine acoustic aspects of them. This paper will examine how consonant clusters are represented using a nonlinear phonological framework. A review of literature on consonant cluster development will provide the necessary background information to discuss the relevant timing issues. In addition, two current models of language processing (Serial Model, Garrett, 1994; Parallel Interactive Model, Stemberger, 1985a and b) will be reviewed to examine how they might deal with the issue 1 of epenthesis and the relationship between the underlying representation and phonetic level of these consonant clusters. Children's consonant cluster productions have been examined at the surface or realization level. Detailed explanations exist of the varying processes (e.g. deletion of one consonant, substitutions) that seem to occur before a child's consonant cluster productions match an adult model. However, very few studies have looked at consonant cluster acquisition while considering the underlying representation level of a child's phonology. In recent years, emphasis has shifted to investigating child phonological development with respect to a specific phonological theory, allowing for the consideration of the relationship between the underlying phonology and the output (i.e. the surface level). In one of the few studies which considered an underlying representation of a child's phonological system, Chin and Dinnsen (1992), using a two-level generative phonology framework, found that a systematic relationship could be described between adult representations and children's underlying representations as well as between children's underlying and phonetic representations of consonant clusters. Since then, more advanced versions of nonlinear frameworks have evolved which have been shown to account better for many phonological occurrences (Bernhardt, 1992). One major purpose of this paper is to examine the consonant cluster productions of two children using a current nonlinear phonology framework. PHONOLOGY VERSUS PHONETICS In the field of speech/language pathology, it is the practice