Cortical color blindness, or cerebral achromatopsia, has been likened by some authors to ''blindsight'' for color or an instance of ''covert'' processing of color. Recently, it has been shown that, although such patients are unable to identify or discriminate hue differences, they nevertheless show a striking ability to process wavelength differences, which can result in preserved sensitivity to chromatic contrast and motion in equiluminant displays. Moreover, visually evoked cortical potentials can still be elicited in response to chromatic stimuli. We suggest (...) that these demonstrations reveal intact residual processes rather than the operation of covert processes, where proficient performance is accompanied by a denial of phenomenal awareness. We sought evidence for such covert processes by conducting appropriate tests on achromatopsic subject M.S. An ''indirect'' test entailing measurement of reaction times for letter identification failed to reveal covert color processes. In contrast, in a forced choice oddity task for color, M.S. was unable to verbally indicate the position of the different color, but was surprisingly adept at making an appropriate eye movement to its location. This ''direct'' test thus revealed the possible covert use of chromatic differences. (shrink)

It is tempting to assume that metacognitive processes necessarily evoke awareness. We review a number of experiments in which cognitive schema have been shown to develop without awareness. Implicit learning of a novel schema may not involve metacognitive regulation per se. Substitution of one automatic process by another as a result of the inadequacy of the former as circumstances change does, however, clearly involve metacognitive and executive processes of error correction and schema selection. We describe a recently published study in (...) which we serendipitously discovered that a blindsight subject could change the schema with which he processed cue information in orienting spatial attention task without reporting any awareness of this change, or of the cues and targets which respectively directed and were the object his attention. (shrink)

In this introductory paper, we assess the current status of blindsight -- the phenomenon in which patients with damage to their primary visual cortex retain the ability to detect, discriminate and localize visual stimuli presented in areas of their visual field in which they report that they are subjectively blind. Blindsight has garnered a great deal of interest and critical research, in part because of its important implications for the philosophy of mind. We briefly consider why this is so, and (...) then go on to examine three empirical questions which have fuelled challenges to the validity of blindsight as a distinct neuropsychological phenomenon. First, is blindsight simply degraded normal vision? Second, does blindsight depend on undamaged areas of primary visual cortex? Third, does evidence that blindsight patients are aware of moving stimuli undermine the apparent dissociation between access to visual information and visual experience in blindsight? In the course of the review we introduce the four other papers on blindsight in this issue. We conclude that, although patients with primary visual cortex damage may indeed perceive moving stimuli, there is still good evidence for a dissociation between access to information and phenomenal experience which cannot be accounted for in terms of degraded normal vision or undamaged primary visual cortex. (shrink)

Can we learn without consciousness? When the eminent neuropsychologist, Lawrence Weiskrantz first coined the term 'blindsight' to describe a condition whereby a patient could demonstrate that they were aware of some object, yet insist that they were completely unaware of its existence, the response from some in the scientific community was one of extreme skepticism. Even now, there are those who question the existence of unconscious learning, and the topic remains one of the most actively researched and debated in psychology. (...) In recent years evidence for unconscious processing across a range of sensory modalities have come from studies of vision, audition, memory, emotion, and action. Never before have these studies of unconscious processing in the different senses been brought together into a single volume. In a book dedicated to Lawrence Weiskrantz, some of the leading psychologists and cognitive neuroscientists of the day explain what we know about unconscious processing in the different senses. Including contributions from, amongst others, David Milner, Jon Driver, Alan Cowey, and Ray Dolan, the book presents a state of the art account of what we now know about 'the unconscious'. The book will provide a fascinating account for students and researchers in psychology, cognitive neuroscience, and philosophy. (shrink)