The nature of blindsight: implications for current theories of consciousness

Blindsight refers to preserved visual abilities in people with damage to the primary visual cortex who report no visual awareness. This phenomenon has been crucial for studying consciousness. Two main models have been proposed: blindsight as perception without consciousness, or as degraded conscious vision. This article re-examines the debate using recent findings. It defines blindsight subtypes—type I, type II, and blindsense—and stresses the need for sensitive methods to reveal dissociations between perception and awareness. The authors argue that the patterns of dissociation are richer than either model suggests, and they discuss implications for current theories of consciousness.

Study at a glance

Abstract

Abstract Blindsight regroups the different manifestations of preserved discriminatory visual capacities following the damage to the primary visual cortex. Blindsight types differentially impact objective and subjective perception, patients can report having no visual awareness whilst their behaviour suggests visual processing still occurs at some cortical level. This phenomenon hence presents a unique opportunity to study consciousness and perceptual consciousness, and for this reason, it has had an historical importance for the development of this field of research. From these studies, two main opposing models of the underlying mechanisms have been established: (a) blindsight is perception without consciousness or (b) blindsight is in fact degraded vision, two views that mirror more general theoretical options about whether unconscious cognition truly exists or whether it is only a degraded form of conscious processing. In this article, we want to re-examine this debate in the light of recent advances in the characterization of blindsight and associated phenomena. We first provide an in-depth definition of blindsight and its subtypes, mainly blindsight type I, blindsight type II and the more recently described blindsense. We emphasize the necessity of sensitive and robust methodology to uncover the dissociations between perception and awareness that can be observed in brain-damaged patients with visual field defects at different cognitive levels. We discuss these different profiles of dissociation in the light of both contending models. We propose that the different types of dissociations reveal a pattern of relationship between perception, awareness and metacognition that is actually richer than what is proposed by either of the existing models. Finally, we consider this in the framework of current theories of consciousness and touch on the implications the findings of blindsight have on these.