THE ROLE OF PROCESSING COMPLEXITY IN WORD ORDER VARIATION AND CHANGE A DISSERTATION SUBMITTED TO THE DEPARTMENT OF LINGUISTICS AND THE COMMITTEE ON GRADUATE STUDIES OF STANFORD UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Harry Tily August 2010 © 2010 by Harry Joel Tily. All Rights Reserved. Re-distributed by Stanford University under license with the author. This work is licensed under a Creative Commons Attribution- Noncommercial 3.0 United States License. http://creativecommons.org/licenses/by-nc/3.0/us/ This dissertation is online at: http://purl.stanford.edu/sr587rm2997 ii I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Thomas Wasow, Primary Adviser I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Arto Anttila I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Daniel Jurafsky I certify that I have read this dissertation and that, in my opinion, it is fully adequate in scope and quality as a dissertation for the degree of Doctor of Philosophy. Roger Levy Approved for the Stanford University Committee on Graduate Studies. Patricia J. Gumport, Vice Provost Graduate Education This signature page was generated electronically upon submission of this dissertation in electronic format. An original signed hard copy of the signature page is on file in University Archives. iii Abstract All normal humans have the same basic cognitive capacity for language. Nevertheless, the world's languages differ in the kind and number of grammatical options they give their speakers to express themselves with. Sometimes, a language's grammatical constructions may differ in how easy they are for comprehenders to process or how readily speakers will choose them. It has been observed that languages which allow more difficult constructions also tend to allow easier ones, and when a language only allows one option, it tends to allow the easiest to process (Hawkins, 1994, 2004). This correlation is intuitive: languages tend to give their speakers options that they find easy to use. However, the causal process that underlies it is not well understood. How did the world's languages come to have this convenient property? In this dissertation, I discuss a family of evolutionary models of language change in which processing- efficient variants tend to be selected more frequently, and hence over time have the potential to displace less efficient variants, pushing them out of the language. I begin by showing that a psycholinguistic theory, dependency length minimization (see e.g. Gibson, 2000, i.a.), accounts for word ordering preferences in data taken from Old and Middle English just as it does in Present Day English. I then discuss computer simulations of a model of language change which implements this bias, predicting observed word order changes in English. Finally, I present experimental studies of online comprehension in Japanese which not only display evidence for the dependency length bias, but also suggest that comprehenders encode it as part of their knowledge about language, using it to help understand the sentences they receive from their peers. iv To my parents, Sally and Rob v Acknowledgments A dissertation is a lot like a tumor. Mine was first diagnosed by my adviser, Tom, who pointed out that some of the topics we had been chatting about during our meetings were beginning to sound dangerously like a dissertation project. Of course, by that point, it had probably been taking form for months or years unnoticed, thanks to earlier exposure to ideas and influences from many others around the department and elsewhere. But it was really only in the last year or so that I recognized how much this dissertation project has grown | seemingly of its own accord | to the point that it has shaped the way I think about almost all aspects of language. Now that I have a final document in front of me, excised and ready to submit, I can much more easily recognize those influences and see how they have grown together. I have many people to thank for my tumor. First and foremost is Tom Wasow, an adviser for whom the word \adviser" isn't an adequate job title. I've received insight, aid, and encouragement from Tom, during the writing of this dissertation and before, that went far beyond anything you could call \advice". I'm honored to have been one of Tom's students. I've also benefited enormously from the input of the other members of my dissertation committee. Roger Levy was originally lured into coming on board to help with a research project that I ended up not including in the dissertation, but instead he managed to give insights and guidance right across the very broad range of topics I foolishly tried to cram into this document. Elizabeth Traugott, who unfortunately couldn't be around during the final revisions and defense, humored some of my strange ideas about language change with interest and open mindedness, while always being able to point me in the right direction when I began to veer into the untenable or simply wrong. I regret vi only beginning to talk to Arto Anttila quite late in the process, since I've found the ideas I gained by doing so eye-opening. Finally, I probably enjoyed my meetings with Dan Jurafsky more than any other academic conversations I've had: Dan is the Brita filter of academic mentors, taking murky and unpalatable half-ideas and making them transparent and appealing almost in real-time. The six years I spent at Stanford were the most intellectually stimulating I have experienced. The atmosphere in the Linguistics Department is scholarly, but fiercely collaborative and supportive, to the point that it sometime feels as though other students and faculty are competing with each other to help, teach, and inspire you the most. My academic path has been shaped enormously by that environment. I'm especially grateful to Joan Bresnan, whose inspiring classes and seminars turned into research projects that gave me the first taste of the empirical linguistics I would end up advocating. I was also lucky to have Florian Jaeger around for the first few years as a trailblazing senpai, and I think any one of our long and fruitful discussions could have worked out as an alternative dissertation project. I've been the willing recipient of his generous advice and ideas ever since. The same holds for many other fellow students here: for instance, Uriel Cohen Priva, Marie-Catherine de Marneffe, Laura Whitton, Laura Staum Casasanto and Philip Hofmeister, just to list a few with impressive-sounding last names. In fact, since so many other students have made my PhD experience so much better, I could just have cut-and-pasted a list from the department website here. But you know who you are. Thank you all! Perhaps more than any of my friends at Stanford, I will miss my former room- mates, Inbal Arnon, Lis Norcliffe, and Scott Grimm; as well as my neighbor, Neal Snider. Between cohabitation, commuting, and collaboration, I ended up sharing most of my life with you for a few wonderful years. And I'd do it all again. Some day in the near future we will get together in San Francisco, cook shakshouka, and reminisce. Finally at Stanford, I owe a huge debt to the department's administrative staff. In particular, Melanie, Gretchen and Alyssa patiently managed to fix every one of my attempts to fail out of the program by getting most bureaucratic and department requirements entirely wrong, and no doubt averted many more similar catastrophes vii behind the scenes. Thank you! Beyond Stanford, I have been lucky enough to visit and work with some of the smartest and most interesting people I can imagine. In Paris, Luc Steels and the members of his group (particularly Remy van Trijp, Wouter Van den Broeck, and Martin Loetzsch) made me welcome in a new and beautiful city, and taught me to think about my research in a very different way. I hope that influence is apparent in this dissertation, as I think it will be in all my work hereafter. At MIT, I was amazed at the brilliant ideas that were thrown around like confetti every day in Ted Gibson's lab. The collaborations which I began there with Ted, as well as Ev Fedorenko, Steve Piantadosi, and Mike Frank have become so important to me that they are now basically what I do, and for that I'm very grateful. A much earlier influence, and perhaps the fundamental reason I followed the path I have ended up on, is that of Antje Meyer, who \adopted" me during my undergrad degree. I got my first taste of a real lab, and of any real collaborative academic environment from Antje and her lab members. Thank you! Just as much as the academic influences, my friends and family are responsible for me having survived grad school. In San Francisco, I'd like to thank Neal and Natalie, Robert, and Fabian for the many good times. Also Melissa, Alexis and Tessa, and all former, current, and (why not) future residents of the infamous house on Church St, where I could and frequently did forget I was a grad student and remember I was a person. In Tokyo, my life has been much better for Vicky Muehleisen, Nobuko Suzuki, John Brooke, Kuki Koibuchi, and Greg Poitevin.