City Research Online City, University of London Institutional Repository Citation: Fassnidge, C. (2018). The Visually-Evoked Auditory Response. (Unpublished Doctoral thesis, City, Universtiy of London) This is the accepted version of the paper. This version of the publication may differ from the final published version. Permanent repository link: https://openaccess.city.ac.uk/id/eprint/19689/ Link to published version: Copyright: City Research Online aims to make research outputs of City, University of London available to a wider audience. Copyright and Moral Rights remain with the author(s) and/or copyright holders. URLs from City Research Online may be freely distributed and linked to. Reuse: Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. 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City Research Online: http://openaccess.city.ac.uk/ [email protected] The Visually-Evoked Auditory Response Christopher James Fassnidge A THESIS SUBMITTED TO THE DEPARTMENT OF PSYCHOLOGY CITY, UNIVERSITY OF LONDON FOR THE DEGREE OF DOCTOR OF PHILOSOPHY March 2018 Table of Contents TABLE OF CONTENTS ............................................................................................................. 2 LIST OF FIGURES .................................................................................................................... 6 LIST OF TABLES ..................................................................................................................... 11 ACKNOWLEDGEMENTS ......................................................................................................... 12 DECLARATION ...................................................................................................................... 13 ABSTRACT ............................................................................................................................ 14 ABBREVIATIONS ................................................................................................................... 15 INTRODUCTION .................................................................................................................... 16 CHAPTER 1: .......................................................................................................................... 16 1.1 INTRODUCTION AND THESIS RATIONALE ................................................................................... 16 1.2 WHAT IS SYNAESTHESIA? ....................................................................................................... 18 1.3 TYPES OF SYNAESTHESIA ........................................................................................................ 20 1.3.1 Audiovisual Synaesthesias ................................................................................... 21 1.3.2 Hearing-Motion Synaesthesia ............................................................................. 23 1.4 DEBATES SURROUNDING SYNAESTHESIA ................................................................................... 25 1.4.1 Rethinking Synaesthesia ...................................................................................... 25 1.4.2 Is Synaesthesia Dichotomous or Continuous? ..................................................... 34 1.4.3 Relationship with Normal Multisensory Integration ........................................... 37 1.4.4 Are Synaesthetic Pairings Environmentally Influenced?...................................... 45 1.5 SUMMARY AND THESIS OUTLINE .............................................................................................. 48 EXPERIMENT 1: THE PREVALENCE, ADVANTAGES, AND PERCEPTUAL REALITY OF VISUALLY- EVOKED SOUNDS. ................................................................................................................ 52 CHAPTER 2: .......................................................................................................................... 52 2 2.1 INTRODUCTION ..................................................................................................................... 52 2.1.1 Prevalence of vEAR .............................................................................................. 54 2.1.2 Objective Measures of Visually-Evoked Sounds .................................................. 57 2.1.3 Controlling for bias/sensory dominance .............................................................. 58 2.2 HYPOTHESES ........................................................................................................................ 60 2.3 METHODS ........................................................................................................................... 62 2.3.1 Participants .......................................................................................................... 62 2.3.2 Apparatus and stimuli ......................................................................................... 62 2.3.3 Design .................................................................................................................. 64 2.3.4 Procedure............................................................................................................. 65 2.4 RESULTS .............................................................................................................................. 72 2.4.1 Questionnaire results ........................................................................................... 72 2.4.2 Psychophysical Data ............................................................................................ 75 2.5 DISCUSSION ......................................................................................................................... 85 2.6 SUMMARY ........................................................................................................................... 92 EXPERIMENT 2: USING TRANSCRANIAL ALTERNATING CURRENT STIMULATION TO EXPLORE THE NEUROPHYSIOLOGICAL BASIS OF VEAR ................................................................................. 94 CHAPTER 3: .......................................................................................................................... 94 3.1 INTRODUCTION ..................................................................................................................... 94 3.1.1 Cross-activation versus Disinhibition as a Mechanistic Underpinning of vEAR ... 96 3.1.2 Transcranial Electric Stimulation ....................................................................... 101 3.2 METHODS ......................................................................................................................... 108 3.2.1 Participants ........................................................................................................ 108 3.2.2 Apparatus and stimuli ....................................................................................... 109 3.2.3 Design ................................................................................................................ 112 3.2.4 Procedure........................................................................................................... 113 3.3 RESULTS ............................................................................................................................ 115 3.4 DISCUSSION ....................................................................................................................... 121 3 3.5 SUMMARY ......................................................................................................................... 129 EXPERIMENT 3. WHO HEARS VISUAL MOTION, AND WHAT LOOKS LOUDEST? A LARGE-SCALE ONLINE SURVEY ................................................................................................................. 132 CHAPTER 4: ........................................................................................................................ 132 4.1 INTRODUCTION ................................................................................................................... 133 4.2 HYPOTHESES ...................................................................................................................... 136 4.3 METHODS ......................................................................................................................... 138 4.3.1 Materials and Stimuli ........................................................................................ 138 4.3.2 Participants ........................................................................................................ 140 4.3.3 Procedure........................................................................................................... 145 4.4 RESULTS ............................................................................................................................ 152 4.4.1 Demographics .................................................................................................... 152 4.4.2 Crosstabulations ................................................................................................ 155 4.4.3 Visual Stimulus Ratings ..................................................................................... 158 4.4.4 Supplementary Questions .................................................................................