Blindsight is qualitatively degraded conscious vision

Abstract

Blindsight is a neuropsychological condition defined by residual visual function following destruction of primary visual cortex. This residual visual function is almost universally held to include capacities for voluntary discrimination in the total absence of awareness. So conceived, blindsight has had an enormous impact on the scientific study of consciousness. It is held to reveal a dramatic disconnect between performance and awareness and used to motivate diverse claims concerning the neural and cognitive basis of consciousness. Here I argue that this orthodox understanding of blindsight is fundamentally mistaken. Drawing on models from signal detection theory in conjunction with a wide range of behavioral and first-person evidence, I content that blindsight is severely and qualitatively degraded but nonetheless conscious vision, unacknowledged due to conservative response biases. Psychophysical and functional arguments to the contrary are answered. A powerful positive case for the qualitatively degraded conscious vision hypothesis is then presented, detailing a set of distinctive predictions borne out by the data. Such data are further used to address the question of what it is like to have blindsight, as well as to explain the conservative and selectively unstable response criteria exhibited by blindsight subjects. On the view defended, blindsight does not reveal any dissociation between performance and awareness, nor does it speak to the neural or cognitive requirements for consciousness. A foundation stone of consciousness science requires radical reconsideration.