Influences on Parsing Ambiguity
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NORTHWESTERN UNIVERSITY Influences on Parsing Ambiguity A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS for the degree DOCTOR OF PHILOSOPHY Field of Linguistics By Lauren Marie Ackerman EVANSTON, ILLINOIS December 2015 2 c Copyright by Lauren Marie Ackerman 2015 All Rights Reserved 3 ABSTRACT Influences on Parsing Ambiguity Lauren Marie Ackerman The primary goal of this dissertation is to characterize the relative strength of two of the influences on the parser's behavior during ambiguity resolution: coreference dependency formation and verb frame preference. I find that coreference dependency formation exerts a stronger influence on the parser than does verb frame preference, even when verb frame preference is maximized in transitively biased frames. Previous studies have shown local attachment bias initially directs the parser to an embedded object analysis in sentences like (1), in which the DP Annie's melody is locally ambiguous between the embedded object (EO)/matrix subject (MS) analyses (Ferreira and Henderson, 1990). (1) Whenever she was trying to casually hum Annie's melody was beautiful. Additionally, (1) contains a cataphoric pronoun she which triggers an active search for an antecedent, whereby the parser seeks the antecedent only in grammatically sanctioned positions, such as where the antecedent is not c-commanded by the pronoun (Kazanina 4 et al., 2007; van Gompel and Liversedge, 2003). In (1), the closest potential antecedent is Annie. However, it can be the antecedent only if the DP that contains it is analyzed as the MS, thus outside the whenever-clause and not c-commanded by she. A bias toward an early cataphoric dependency formation could lead the parser to analyze the ambiguous DP as the MS. In (1), there is a bias toward a MS analysis from the antecedent search in addition to a bias toward the local attachment EO analysis. I find that, regardless of the transitivity bias of the verb in the position of hums, the parser forms a dependency between the pronoun she and Annie. This indicates that dependency formation can supersede verb frame preferences and any default preference the parser may have toward local attachment (Phillips and Gibson, 1997). Moreover, I also observe effects attributable to both the MS and EO parses. This suggests that the parser builds both alternatives and maintains them in parallel. From this, I conclude that the parser prioritizes information from an ongoing dependency search over lexical properties during ambiguity resolution. 5 Acknowledgements The profound gratitude I feel toward everyone who has helped me along the way, in any capacity, cannot be fully expressed in writing. For all of the power of language which we study as linguists, words simply cannot do my emotion justice. It's a pretty amazing feeling to be at this point where writing an acknowledgements section is appropriate, and not pre-emptive. It has been a very bumpy road for me, and I owe my (scholarly) survival to countless people. I will do my best to name those who played a significant role in my graduate career, but this list is by no means exclusive. First and foremost, none of this would have been possible without the support of my advisor, Masaya Yoshida. His patience with my confusion and his critical comments about my writing and thinking have shaped me as a scholar. He has taught me more about the scientific method and clear, explicit writing than I thought was possible for me to learn. My gratitude goes to Nina Kazanina, whose own dissertation inspired mine, and who has been invaluable in planning and interpreting the experiments herein. Many thanks to Matt Goldrick for his careful, insightful feedback and discussion of my analyses and statistical methods. Beyond my dissertation committee, many others contributed to my progress and the quality of the final product presented here. Brian Dillon suggested the method for checking the correlation between the two critical regions, which lead me to the surprising conclusion that, in fact, the parser represents both alternatives in real time. Megan Risdal talked 6 me through some particularly sticky statistical analysis and terminology, and offered to read some of the longest and driest sections for clarity. Laura Bailey was an excellent accountability buddy, in which she would tweet at me to start working in the morning, and I would tweet to go to bed at night. Maryam Bakht and Barbara Clark were wonderful professional role models, who both talked me down when I needed nonjudgmental adult supervision, and offered to proofread early drafts. Shiloh Drake has been an amazing friend and supportive writing buddy, who has always had time for me and who introduced me to the fantastic group who I now refer to as GALizona. GALizona (Shiloh Drake, Mary-Caitlyn Valentinsson, Elise Bell, and Megan Figueroa) as a group and as individuals have been wonderful, motivational grad school compatriots, despite the hundreds of miles between us. Ann Burchfield has been a dear friend and colleague with whom I've explored cities and trails, and shared many deep conversations about linguistics and life. Mike Frazier has been a fantastic collaborator and friend. We have battled code and equipment and manuscripts side by side, and it has been an honor to do so. Karen Chu has been the most generous and supportive friend throughout my time in grad school. It was written in the stars that we would cross paths and help each other achieve our goals. Even though we've gone different directions in our careers, it is Karen who I think best understands the scholarly path I've taken (not least because of her skillful editing!). In contrast, my sister in spirit Sonia Saraiya and I have taken very different career paths, yet we find ourselves in similar places. After having such different interests for over a decade, we end up both spending our time writing and finding ways to structure our time so that we don't get sucked into Netflix (albeit for different reasons!). 7 I would be remiss if I did not acknowledge the incredible community of linguists on Twitter (my so-called twitterlings). This community of sharing knowledge, ideas, insights, institutionally-restricted access to peer-reviewed articles, and mundane happenings has kept me grounded and motivated. Notably, Gretchen McCulloch has, in my mind, served as my foil, inspiration, and a window into the world of popular science communication. She helped me to see how wonderful life can be outside academia and showed me that I can continue my work as an advocate and communicator of linguistics from within academia. (And I can leave the time-consuming projects to her, since she's getting paid to do it!) My family has been a tremendous source of strength and motivation for me. My grand- mother, Sydel Ackerman, asks me to explain what I'm working on, listens with patience and wonder, and with her keen insight, asks me pointed questions that help me find ways to talk about my work without resorting to jargon. Her support, especially within the last (tumultuous) year, has been invaluable. My parents have given me unconditional love and support my whole life, the value of which has become particularly clear throughout grad school. My mother, Adrienne Tymiak, always has time to talk me through dealing with impostor syndrome, based on her own experiences and wisdom. She showed me the value in forging a unique path through life and career, no matter how difficult. Her strength and tenacity taught me how to fight for my dreams. My father, David Ackerman, instilled in me the value of honesty and integrity from a young age, and has kept me curious about the world in all of the infinite ways one can study it, scientifically and artistically. He helped me hone a process for thinking logically (which I have always struggled with) by use of flowcharts, and pushed me to think about problems from new perspectives. My brother, Paul Ackerman, who is also working to finish his dissertation at this moment, 8 has probably been the most influential teacher in my family. He is so incredibly smart and quick to pick up new concepts, it has been an honor to discuss linguistics and natural language processing with him. In turn, he has taught me about chiral liquid crystals. Our discussions have taught me to think more computationally, and have strengthened my work ethic and tenacity. He is one of the most important role models in my life. In turning my attention to my most immediate family, I will address Leeroy Jenkins and Loki with a quote from Ross(1967), \Since in my view, cats are as necessary as air or water, I thank our cats . for deigning to stay with us and seasoning our existence." But to return to a more sombre tone, it is Thomas Bergman to whom I am most deeply and sincerely grateful. Without Tom's continuous, loving presence in my life for the last ten years, none of this would have been possible. He has made me laugh when I felt hopeless, fed me when I was overwhelmed, and made sure I got out and interacted with friends occasionally. It is for these reasons, among many, many others, that I dedicate this dissertation to Tom, the most wonderful, loving, open, and honest spouse a person could dream of. 9 Table of Contents ABSTRACT3 Acknowledgements5 List of Tables 15 List of Figures 16 Chapter 1. Introduction 18 Chapter 2. Survey of Literature 25 2.1. The parser 25 2.1.1. Serial parsers 27 2.1.1.1. Kimball(1973) 27 2.1.1.2. Frazier and Fodor(1978) 27 2.1.1.3.