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This thesis has been submitted in fulfilment of the requirements for a postgraduate degree (e.g. PhD, MPhil, DClinPsychol) at the University of Edinburgh. Please note the following terms and conditions of use: This work is protected by copyright and other intellectual property rights, which are retained by the thesis author, unless otherwise stated. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the author. The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the author. When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given. Context, Cognition and Communication in Language James Winters Doctor of Philosophy School of Philosophy, Psychology, and Language Sciences University of Edinburgh 2016 Declaration I declare that this thesis was composed by myself and that the work contained therein is my own, except where explicitly stated otherwise in the text. (James Winters) 3 4 Abstract Questions pertaining to the unique structure and organisation of language have a long history in the field of linguistics. In recent years, researchers have explored cultural evolutionary explanations, showing how language structure emerges from weak biases amplified over repeated patterns of learning and use. One outstand- ing issue in these frameworks is accounting for the role of context. In particular, many linguistic phenomena are said to to be context-dependent; interpretation does not take place in a void, and requires enrichment from the current state of the conversation, the physical situation, and common knowledge about the world. Modelling the relationship between language structure and context is therefore crucial for developing a cultural evolutionary approach to language. One approach is to use statistical analyses to investigate large-scale, cross-cultural datasets. However, due to the inherent limitations of statistical analyses, espe- cially with regards to the inadequacy of these methods to test hypotheses about causal relationships, I argue that experiments are better suited to address ques- tions pertaining to language structure and context. From here, I present a se- ries of artificial language experiments, with the central aim being to test how manipulations to context influence the structure and organisation of language. Experiment 1 builds upon previous work in iterated learning and communication games through demonstrating that the emergence of optimal communication sys- tems is contingent on the contexts in which languages are learned and used. The results show that language systems gradually evolve to only encode information that is informative for conveying the intended meaning of the speaker { resulting in markedly different systems of communication. Whereas Experiment 1 focused on how context influences the emergence of structure, Experiments 2 and 3 inves- tigate under what circumstances do manipulations to context result in the loss of structure. While the results are inconclusive across these two experiments, there is tentative evidence that manipulations to context can disrupt structure, but only when interacting with other factors. Lastly, Experiment 4 investigates whether the degree of signal autonomy (the capacity for a signal to be inter- 5 preted without recourse to contextual information) is shaped by manipulations to contextual predictability: the extent to which a speaker can estimate and ex- ploit contextual information a hearer uses in interpreting an utterance. When the context is predictable, speakers organise languages to be less autonomous (more context-dependent) through combining linguistic signals with contextual information to reduce effort in production and minimise uncertainty in compre- hension. By decreasing contextual predictability, speakers increasingly rely on strategies that promote more autonomous signals, as these signals depend less on contextual information to discriminate between possible meanings. Overall, these experiments provide proof-of-concept for investigating the relationship between language structure and context, showing that the organisational principles under- pinning language are the result of competing pressures from context, cognition, and communication. 6 Acknowledgements A thesis is very rarely the product of a single individual. Like language, it grad- ually emerges from repeated interactions { and this thesis is no exception. Special thanks go to my two supervisors, Simon Kirby and Kenny Smith, for giving me the opportunity to do a PhD in the first place and for their support and advice throughout my time at Edinburgh. You guys are a continual source of intellectual inspiration. (Additional thanks to Kenny for continuing the tradition of explaining the difference between a shovel and a spade to this na¨ıve learner.) For being a long-term collaborator, Replicated Typo co-founder, groomsman, and, most importantly, a good friend, I thank Se´an Roberts. Without the financial support of the AHRC this PhD could not have happened. I hope I was a good investment. There are many others who have contributed in various ways to this thesis over the last five years. I would like to thank, wholeheartedly: The inhabitants of office 1.15 (both past and present): Mark Atkinson, Kevin Stadler, Matt Spike, Catriona Silvey, Yasamin Motamedi, Carmen Salda~na,Marieke Woensdregt, Thijs Lubbers, Vanessa Ferdinand, Bill Thompson, Jasmeen Kan- wal, Alan Nielsen, George Starling, Steph DeMarco, James Thomas, Justin Sulik, Soundness Azzabou-Kacem, Rea Colleran, Jon Carr, Daniel Lawrence, Andrea Ravignani, Ashley Micklos, Christoph Hesse, Elyse Jamieson, Cathleen O'Grady, and John-Sebastian Schutter. The various individuals involved with the LEC (now CLE) in some capacity or another, especially: Thom Scott-Phillips, Monica Tamariz, Graeme Trousdale, Christine Cuskley, Chris Cummins, Rob Truswell, Richard Blythe, Jennifer Cul- bertson, Jim Hurford, Olga Feh´er,Marieke Schouwstra, Tessa Verhoef, Gareth Roberts, and Hannah Cornish. My new academic home at the Mint: Olivier Morin, Piers Kelly, Thomas M¨uller, Lidiia Romanova, and Barbara Pavlek. The readers of Replicated Typo and the contributors who make it possible (I promise that I'll spend more time writing posts now that this thesis is finished): Michael Pleyer, Stefan Hartmann, Hannah Little, Anne Pritchard, Bill Benzon, Christian Kliesch, Jess Hrebinka, Keelin Murray, Richard Littauer, and Rachael Bailes. For unbounded support (both emotional and financial) throughout the years I would like to thank my family, especially my Mum, Dad, and my brother Chris. Finally, for keeping me sane over the last few years, being continually patient, and making the insane commitment to marry a penniless and stressed PhD student, I would like to thank my wife, Maria Brackin. You make it all worthwhile. 8 Contents Abstract 6 1 Introduction 11 1.1 Introduction . 11 1.2 What is context? . 13 1.3 Filling the expressive gaps . 17 1.4 The interaction of minds and data . 18 1.4.1 Discrimination Pressure: Context and Expressivity . 22 1.4.2 Generalisation Pressure: Cognition and Simplicity . 24 1.4.3 Coordination Pressure: Communication and Convention . 26 1.5 Methodological Commitments . 30 1.6 Thesis road map . 31 2 Languages adapt to their contextual niche 33 2.1 Introduction . 33 2.2 Author contributions . 34 2.3 Winters, Kirby & Smith (2015): Languages adapt to their contex- tual niche . 34 2.4 Conclusion . 71 3 From cup board to cupboard: The loss of compositionality in linguistic systems 73 3.1 Introduction . 73 3.1.1 Loss of compositionality: reuse, chunking, and context . 75 3.1.2 Modelling the loss of compositionality . 78 3.2 Experiment 2 . 82 3.2.1 Method . 82 3.2.2 Dependent Variables and Hypotheses . 84 3.2.3 Results . 86 3.2.4 Experiment 2 Discussion . 90 9 3.3 Experiment 3 . 95 3.3.1 Shape Bias or Unbalanced Dimensions? . 95 3.3.2 Method . 95 3.3.3 Results . 97 3.3.4 Experiment 3 Discussion . 102 3.4 Design Issues and Future Directions . 106 3.4.1 Changes to the meaning space . 106 3.4.2 Changes to the context . 107 3.4.3 Changes to the task . 107 3.5 Conclusion . 108 4 Signal autonomy is shaped by contextual predictability 111 4.1 Introduction . 111 4.2 Author contributions . 112 4.3 Winters, Kirby & Smith (submitted): Signal autonomy is shaped by contextual predictability . 112 4.4 Conclusion . 170 5 Linguistic diversity and traffic accidents 171 5.1 Introduction . 171 5.2 Author contributions . 173 5.3 Roberts & Winters (2013): Linguistic diversity and traffic accidents 173 5.4 Conclusion . 187 6 Conclusion 189 Appendices 241 Appendix A: Languages Experiment 1 . 241 Appendix B: Languages Experiment 2 . 243 Appendix C: Languages Experiment 3 . 244 Appendix D: Languages Experiment 4 . 245 10 Chapter 1 Introduction 1.1 Introduction \Why did you write that?" asked the supervisor. \Because I thought it would be a good example," replied the student. What at first might seem like an unremark- able and commonplace interaction is in fact a demonstration of an ability found only in humans (Pinker, 1994). By using a set of sounds, strung together in a particular sequence, the student and supervisor are able to convey their thoughts to one another. This capacity to express almost any thought, and have someone else understand your expression and reply