Unmasking consciousness: A case study demonstrating the impact of empirical data on theories of consciousness

Date of Completion

January 2009






This dissertation focuses on philosophically motivated theories of consciousness which attempt to account for the time-course development of consciousness in the brain, from stimulus onset to conscious report, specifically for visual stimuli. As a case study, I select three researchers in consciousness studies with very different approaches to the topic: philosophers Daniel Dennett and Fred Dretske, and cognitive neuropsychologist Victor Lamme. I argue that data acquired from metacontrast backward visual masking—a phenomenon wherein a non-spatially overlapping visual stimulus presented later in time is associated with the reduced discernibility of a prior visual stimulus—demonstrate that each theoretician runs into serious difficulties accounting for metacontrast within the constraints of their theories; indeed, these difficulties undermine critical components of their theories. ^ I then articulate a view of how we should proceed in the scientific study of consciousness by first gleaning important insights salvageable from the above mentioned projects. For example, although I argue against Dennett's characterization of problems confronting researchers interested in distinguishing between conscious and unconscious processes, I largely support Dennett's description of how scientists do and should proceed in the scientific study of consciousness—this is what Dennett calls 'heterophenomenology'. I also argue against Dretske's test for awareness, which is based on his information theoretic account of perception, while supporting Dretske's project to carefully articulate specific tests both for awareness and for perception without awareness. And, finally, I agree that findings in neurology should play a greater role in determining when we attribute consciousness (or a lack thereof) to subjects, while arguing, against Lamme, that such a role will always ultimately rest on subjective reports. ^