Accounting for Diphthongs: Duration As Contrast in Vowel Dispersion Theory
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ACCOUNTING FOR DIPHTHONGS: DURATION AS CONTRAST IN VOWEL DISPERSION THEORY A Dissertation submitted to the Faculty of the Graduate School of Arts and Sciences of Georgetown University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Linguistics By Stacy Jennifer Petersen, M.S. Washington, DC June 12, 2018 Copyright ©2018 by Stacy Jennifer Petersen All Rights Reserved ii ACCOUNTING FOR DIPHTHONGS: DURATION AS CONTRAST IN VOWEL DISPERSION THEORY Stacy Jennifer Petersen, M.S. Thesis Advisor: Elizabeth Zsiga, Ph.D. ABSTRACT This dissertation investigates the production and perception properties of diphthong vowels at different speech rates in order to advance the understanding of diphthong phonetics and to incorporate diphthongs into the phonological theory of vowel dispersion. Dispersion Theory (Flemming, 2004; Liljencrants & Lindblom, 1972; Lindblom, 1986) models vowel inventories in terms of contrast between all vocalic elements, yet currently only accounts for quality contrasts. Problematically, diphthongs have been excluded from previous acoustic and theoretical work due to their complex duality of being composed of two vowel targets while acting as one phonological unit. Two experiments are presented which test diphthong production and perception by altering speech rate and duration to determine fundamental properties of diphthongs cross-linguistically. In an elicitation experiment that uses a novel methodology for speech rate modulation, it is shown that speakers maintain diphthong endpoint targets in Vietnamese, Faroese, and Cantonese. Both diphthong endpoints and monophthong targets show similar movement as a natural effect of reduction of the vowel space at faster speech rates, unifying monophthongs and diphthongs in terms of their phonetic properties. Contra the predictions of Gay (1968), it is shown that diphthong slope is variable across speech rates and slope variability is language- dependent. The second section examines the effect of duration manipulation on diphthong perception with a vowel identification experiment. Results show that the effect of duration manipulation is iii dependent on phonological vowel length, but otherwise increasing duration improves perception through an increase in percent correct, lower confusability, and lower reaction times. Increasing duration also reduces confusability between diphthongs and monophthongs. This study finds that duration is an important dimension of contrast both within diphthongs and the vowel inventory as a whole. The analysis shows that in order to adapt Dispersion Theory to account for diphthongs, the theory must include an additional contrast dimension of time. Based on the results of the experiments, three constraints are proposed to initiate the inclusion of diphthongs into Dispersion Theory: *DUR, MINDIST ONSET, and MINDIST OFFSET. Including duration in theoretical models of vowel dispersion is the first step in accounting for vocalic elements that are contrastive along multiple dimensions. iv ACKNOWLEDGMENTS I am eternally grateful for the dedication, support, and inspiration of several people who made this work possible. First, I must thank my long-time mentor and advisor Lisa Zsiga, who re-inspired my love of phonetics with her incredibly vast knowledge and passion. She has helped me since my first days at Georgetown and working with her and learning from her has been an invaluable experience. I also thank Youngah Do, who first sparked my interest in phonological acquisition and whose rigorous teaching and mentorship challenged and inspired me. She has always encouraged me to look at the bigger picture, and has been very influential for me, even across the globe in Hong Kong. I also would like to thank Jen Nycz for her technical expertise, helpful comments, and constant encouragement. Finally, I thank Hannah Sande, whose immediate help and unwavering kindness quickly made her a close mentor and a valuable member of my committee. I would also like to thank all of my other Georgetown professors, especially Ruth Kramer for her friendly support and enthusiasm. Thank you to all of the experiment participants, whose contributions are at the heart of this work. I owe thanks to all of my helpers in the Linguistics Lab at Georgetown University and the MITRE Corporation. I especially would like to everyone at the University of the Faroe Islands, who readily helped me collect data at their beautiful campus. I owe a large thanks to my many friends and peers at Georgetown who have provided years of insight, fun, and inspiration. Thanks to the PhonLab (née SoundPhiles) members, especially Kate Riestenberg, Alexandra Pfiffner, Amelia Becker, Maya Barzilai, Maddie Oakley, Jon Havenhill, and Shuo Zhang, for putting up with me talking about diphthongs for so long and for essential technical help. To my study buddies and friends Shannon Mooney, Morgan Rood v Staley, Dan Simonson, and Laura Bell: you’re awesome and I can’t thank you enough for all the fun times, long work days, and late nights. Special thanks to my good friends who have been there for me during these long years both in California and DC. To Liz Merkhofer, Christine Harvey, Justin Roy, Kiya Kashanijou, and my D&D group, thank you for keeping me sane and for your constant friendship and love. To Linly Sergel, thank you for the weirdness, moral support, and more wine than you can even account for. This work is dedicated to my loving family—Marilyn, Jerry, and Chris Petersen. Their intellect, creativity, drive, humor, and unwavering support have forever been my foundation and I am forever indebted to them. Last but not least, I dedicate this to Watson, my little ball of unconditional love. vi TABLE OF CONTENTS Chapter 1 Introduction and Literature Review ............................................................................... 1 1.1 Introduction ...................................................................................................................... 1 1.2 Vowel Systems and Dispersion Theory ........................................................................... 2 1.2.1 Introduction ............................................................................................................... 2 1.2.2 Vowel Dispersion...................................................................................................... 3 1.2.3 Diphthong Typology and Markedness .................................................................... 13 1.2.3.1 Typological Trends in Diphthongs .................................................................. 13 1.2.3.2 Diphthong Markedness, Contrast and Confusability ....................................... 22 1.2.4 Diphthongs in Dispersion Theory ........................................................................... 24 1.2.5 Summary ................................................................................................................. 27 1.3 Diphthong Parameters and Definition ............................................................................ 28 1.3.1 Introduction ............................................................................................................. 28 1.3.2 Phonetic Parameters of Diphthongs ........................................................................ 29 1.3.2.1 Targets and Steady States ................................................................................ 33 1.3.2.2 Trajectory/Slope .............................................................................................. 38 1.3.2.3 Summary of Phonetic Parameters .................................................................... 40 1.3.3 Phonological Representation ................................................................................. 41 1.3.3.1 Phonological Contrasts .................................................................................... 42 1.3.3.2 Moraic Structure .............................................................................................. 48 1.3.4 Diphthong Definition .............................................................................................. 49 1.3.4.1 Contour Tone ................................................................................................... 52 1.3.5 Summary ................................................................................................................. 55 vii 1.4 Durational Cues .............................................................................................................. 56 1.4.1 Competing Hypotheses: Slope or Frequencies? ..................................................... 57 1.4.1.1 Slope-Constant Hypothesis.............................................................................. 58 1.4.1.2 Frequency-Constant Hypothesis ...................................................................... 62 1.4.2 Transition Duration Patterns ................................................................................... 65 1.4.3 Summary ................................................................................................................. 72 1.5 Chapter Overview .......................................................................................................... 72 Chapter 2 Production Experiment ................................................................................................. 74 2.1 Introduction .................................................................................................................... 74 2.2 Language Background...................................................................................................