
A Philosophical Examination of Working Memory by Max Hanson Beninger Department of Philosophy Duke University Date:_______________________ Approved: ___________________________ Karen Neander, Co-Supervisor ___________________________ Felipe De Brigard, Co-Supervisor ___________________________ Owen Flanagan ___________________________ Marty Woldorff ___________________________ Carlotta Pavese Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Philosophy in the Graduate School of Duke University 2019 ABSTRACT A Philosophical Examination of Working Memory by Max Hanson Beninger Department of Philosophy Duke University Date:_______________________ Approved: ___________________________ Karen Neander, Co-Supervisor ___________________________ Felipe De Brigard, Co-Supervisor ___________________________ Owen Flanagan ___________________________ Marty Woldorff ___________________________ Carlotta Pavese An abstract of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Philosophy in the Graduate School of Duke University 2019 Copyright by Max Hanson Beninger 2019 Abstract Working memory—the mental capacity to “hold on to” information after it ceases to be perceptually available—is one of the most discussed topics in psychology and neuroscience. Despite the importance of working memory in the sciences, however, there is only a small amount of philosophical research on the topic. The aim of my dissertation is to provide a philosophically-informed account of working memory, and to assess its relationship to other mental phenomena, including attention and consciousness. In chapter one, I provide a broad historical overview of working memory. I begin by outlining William James’ original distinction between “primary” and “secondary” memory, and work my way up to present-day neuroscientific investigations of working memory. One of the main conclusions of this chapter is that there is no working memory “module” in the brain. Instead, working memory is best conceptualized as a functionally-defined process that is potentially realized by multiple neural mechanisms. In chapter two, I explore the link between working memory and attention. Recent evidence from psychology and neuroscience indicates that attention is (to some extent) involved in the process of working memory maintenance. However, it remains unclear whether the contents of working memory are always attended, or if working memory representations can be dynamically shifted in and out of the focus of attention. Drawing on empirical and phenomenological data, I argue that the second view is iv correct. Although attention plays an important role in working memory maintenance, working memory representations can persist—at least temporarily—outside the focus of attention. Chapter three addresses a related question: namely, how working memory relates to consciousness. I distinguish three possible positions on this score: (i) working memory representations are always conscious; (ii) working memory representations can be either conscious or unconscious, but they are all accessible to consciousness; and (iii) working memory representations can be either conscious or unconscious, and some are inaccessible to consciousness. Based on the available empirical data, I argue in favor of position (ii). Evidence suggests that working memory representations can be unconscious, but such unconscious representations still appear to be consciously accessible, in the sense that they can be brought to consciousness at will. Finally, in chapter four, I provide a critique of Peter Carruthers’ recent sensory- based account of working memory. According to Carruthers, attention only targets “mid-level” sensory areas, and thus the representations held in working memory will necessarily be sensory based in nature. I disagree. I point out that there is some evidence for attentional modulation outside of modality-specific sensory areas. I also highlight several empirical studies which provide preliminary support for the existence of non- sensory (i.e., amodal) working memory representations. v Dedication To Sam—I couldn’t have done it without you. vi Contents Abstract ................................................................................................................................... iv List of Figures ........................................................................................................................... x Acknowledgements ................................................................................................................xi 1. Introduction .......................................................................................................................... 1 1.1 Historical preliminaries ............................................................................................... 3 1.1.1 Atkinson & Shiffrin’s model ................................................................................... 4 1.1.2 Fractionating the short-term store: Baddeley & Hitch’s multi-component model ................................................................................................................................ 9 1.2 The neuroscience of working memory ..................................................................... 12 1.3 The metaphysics of working memory ...................................................................... 19 1.3.1 Reductionism vs. anti-reductionism .................................................................... 19 1.3.2 A functional account of working memory .......................................................... 23 1.3.3 Eliminating working memory? ............................................................................ 29 1.4 Three questions .......................................................................................................... 31 1.4.1 How is working memory related to attention? ................................................... 32 1.4.2 How is working memory related to consciousness? .......................................... 34 1.4.3 Is working memory “sensory based”? ................................................................. 35 2. Attention to working memory representations: Sustained or sporadic? ....................... 37 2.1 Background ................................................................................................................. 39 2.1.1 Working memory .................................................................................................. 39 2.1.2 Attention ................................................................................................................ 41 vii 2.2 Evidence that working memory maintenance involves attention .......................... 45 2.3 Working memory representations outside the focus of attention .......................... 50 2.3.1 Phenomenological and behavioral considerations ............................................. 51 2.3.2 Neural evidence for unattended working memory representations ................. 54 2.3.3 How are unattended working memory representations stored in the brain? .. 57 2.4 The capacity of attention ............................................................................................ 60 2.5 Conceptual issues ....................................................................................................... 66 2.6. Conclusion ................................................................................................................. 69 3. Working memory, consciousness, and conscious accessibility ....................................... 71 3.1 Different kinds of consciousness? ............................................................................. 73 3.2 Evidence that working memory and consciousness are related ............................. 80 3.3 Working memory representations are not always consciously accessed .............. 84 3.4 Subliminal working memory .................................................................................... 91 3.5 Conclusion .................................................................................................................. 98 4. Is working memory sensory-based? ............................................................................... 100 4.1 Carruthers’ sensory-based account ......................................................................... 102 4.1.1 Consciousness and attention .............................................................................. 103 4.1.2 Working memory as stimulus-absent broadcasting ......................................... 105 4.2 The targets of attention argument ........................................................................... 108 4.3 Evidence for non-sensory working memory .......................................................... 114 4.3.1 Electrophysiological studies ............................................................................... 115 4.3.2 Neuroimaging data ............................................................................................. 118 viii 4.3.3 Aphantasia ........................................................................................................... 121 4.4 The positive picture.................................................................................................. 123 4.4.1 A multi-level model of working memory storage ............................................ 123
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