Detection of Longitudinal Development of Dementia in Literary Writing A thesis presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Master of Arts Torri E. Raines May 2018 © 2018 Torri E. Raines. All Rights Reserved. 2 This thesis titled Detection of Longitudinal Development of Dementia in Literary Writing by TORRI E. RAINES has been approved for the Department of Linguistics and the College of Arts and Sciences by David Bell Associate Professor of the Department of Linguistics Robert Frank Dean, College of Arts and Sciences 3 ABSTRACT RAINES, TORRI E., M.A., May 2018, Linguistics Detection of Longitudinal Development of Dementia in Literary Writing Director of Thesis: David Bell Past studies have suggested that the progression of dementia, especially Alzheimer’s disease, can be detected in the writing of literary authors through analysis of their lexical diversity patterns. However, those studies have used oversimplified measures and vague definitions of lexical diversity. This study uses a multi-faceted, computationally operationalized model of lexical diversity innovated by Scott Jarvis to analyze a total of 129 novels by five authors (three with dementia and two without), with the purpose of identifying the lexical characteristics of dementia in literary writing. A total of 22 novels by two authors with suicidal depression were also analyzed in order to determine whether this condition also leads to changes in authors’ lexical diversity patterns. Analyses were conducted with six individual lexical diversity measures and two supplementary lexicosyntactic measures. Results suggest that dementia as well as the effects of healthy aging manifest in different aspects of lexical diversity for different authors, and that this model of lexical diversity is a robust tool for detecting lexical decay indicative of dementia. The model achieves 100% classification accuracy in discriminating between dementia-affected and non-dementia-affected novels. Classification accuracy drops slightly with leave-one-out cross-validation but remains higher than 88% for all dementia group authors. 4 DEDICATION To my fiancé and life partner, Zachary Thompson, and our ridiculous cats, Harley and Pickle. 5 ACKNOWLEDGMENTS I am grateful to Dr. Scott Jarvis for his invaluable guidance, feedback, and encouragement throughout this project and for getting me interested in lexical diversity and computational linguistics in the first place. I would like to thank my other committee members, Dr. David Bell and Dr. Michelle O’Malley, for their enthusiasm and input. I also extend my gratitude to Dr. Romy Ghanem for help with using SPSS and interpreting statistics. As always, my fiancé Zachary Thompson has my endless gratitude for emotional and intellectual support that made the completion of this project possible. I also want to thank him for his help with various coding problems throughout the process. 6 TABLE OF CONTENTS Page Abstract .................................................................................................................................................. 3 Dedication ............................................................................................................................................. 4 Acknowledgments ................................................................................................................................ 5 Table of Contents ................................................................................................................................. 6 List of Tables ........................................................................................................................................ 8 List of Figures ....................................................................................................................................... 9 Chapter 1: Introduction ..................................................................................................................... 10 Chapter 2: Literature review ............................................................................................................. 12 Alzheimer’s and Dementia Detection ...................................................................................... 12 Measuring Lexical Diversity ....................................................................................................... 16 Depression Detection ................................................................................................................. 21 The Present Study ....................................................................................................................... 24 Chapter 3: Method ............................................................................................................................. 26 Data ............................................................................................................................................... 26 Authors ......................................................................................................................................... 28 Analysis ......................................................................................................................................... 38 Lexical Diversity ................................................................................................................... 38 Other measures ..................................................................................................................... 42 Chapter 4: Results and Discussion .................................................................................................. 46 Individual variables and linear regression ................................................................................ 46 Control Group ...................................................................................................................... 47 Dementia Group ................................................................................................................... 52 Depression Group ................................................................................................................ 64 Exploratory – Hierarchical Cluster Analysis ........................................................................... 68 Confirmatory – Linear Discriminant Analysis ........................................................................ 73 Dementia Group ................................................................................................................... 73 Depression Group ................................................................................................................ 81 Returning to Research Questions ............................................................................................. 82 RQ1 - Will complex measures of lexical diversity support the findings of Le et al.’s 2011 study? ............................................................................................................................ 82 7 RQ2 - Will these measures provide more nuanced detection of the development of dementia? ............................................................................................................................... 83 RQ3 - Can these measures be applied to depression, and particularly depression escalating into suicide? ......................................................................................................... 85 Limitations to the Study and Future Directions ..................................................................... 85 Chapter 5: Conclusion ....................................................................................................................... 88 References ........................................................................................................................................... 90 Appendix A: Sample Data ................................................................................................................ 96 Appendix B: Significant Linear Regression Graphs ...................................................................... 97 Appendix C: Dendogram from Hierarchical Cluster Analysis ................................................. 105 8 LIST OF TABLES Page Table 1. Iris Murdoch novels used ................................................................................................. 29 Table 2. Agatha Christie novels used ............................................................................................. 31 Table 3. Terry Pratchett novels used .............................................................................................. 33 Table 4. P.D. James novels used ..................................................................................................... 34 Table 5. Mary Higgins Clark novels used ...................................................................................... 35 Table 6. Virginia Woolf novels used .............................................................................................. 37 Table 7. Kurt Vonnegut novels used ............................................................................................. 38 Table 8. Raw LD and it-v-adj-to-that values for P.D. James ...................................................... 48 Table 9. Linear regression results for P.D. James ........................................................................ 48