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In a number of tests, D. B. reported an impression of ‘waves’ generated by some visual stimuli, especially in a ‘lively’ part of his field defect (a region between the fovea and about 30° in the lower quadrant). The waves could have some ‘sort of form’, or could be ‘quick’, ‘slow’, ‘sharp’, or ‘curved’. When the waves were experienced they were difficult for him to ignore, but they could seriously mislead him when they were used as a basis for differential discriminations. Accordingly, special pains were taken to see whether good discrimination was still possible when conditions were arranged to eliminate the waves. This was done by increasing ambient illumination with bright overhead lamps or by using low contrast stimuli. The results showed that his discrimination was still excellent in a variety of situations, even though he reported ‘nothing there’, ‘absolutely nothing’, or ‘just guessing’. D. B. often seemed to settle into a sort of experience-less ‘blindsight mode’ when he performed well but automatically and without fatigue, in contrast to his good field when long series of discrimination tests produced tiredness.

‘D. B.’ is the subject of the book who underwent intensive tests of his blindsight. His visual cortex in one hemisphere was removed surgically to excise an invasive tumour when he was 33 years old. The findings of Pöppel et al. (1973) were confirmed, in which brain damaged subjects could move their eyes to the location of an ‘unseen’ stimulus in their blind fields. The use of animal testing methods were then applied by asking D. B. to guess the location of stimuli by reaching for them. He was also asked to guess between two alternatives: whether a line was horizontal or not, and whether a stimulus was a particular shape or an alternative shape. Asking him to guess whether a sine-wave grating or a homogenous luminous-matched patch was present or not made it possible to measure his visual acuity and compare it with that of the intact visual hemifield. Following a battery of tests, his verbal commentaries were recorded in which he characteristically said he was just guessing and thought he was ‘at chance’ because he could not see anything, although in some tests he had a ‘feeling’ that something was there.

This chapter discusses a selected set of neuropsychological disorders and enquires whether analysis of eye movements can help explain the nature of the disorder. It argues that the study of such patients can in turn inform theories of vision and visual cognition. The chapter starts with a discussion of blindsight, visuo-spatial neglect, Balint's syndrome, and disorders that result from damage to the frontal lobe. The second half of the chapter concentrates on a single case, AI, who is not able to generate eye movements and so instead generates saccade-like movements of her head. The case is discussed as an example of peripheral neuropsychology, and the implications for the active vision framework are emphasized.

This chapter argues that sensory consciousness gives us our most vivid moment-to-moment experiences. Mental images seem to be “faint copies” of sensory events, generated from within the brain itself. As far as the brain is concerned, sensations and images belong together. Abstract ideas, on the other hand, allow us to transcend the limitations of the perceptual world in time and space, to enter the many realms of abstraction. The parts of the human cortex that support abstract thinking seem relatively recent on an evolutionary scale, and may ride on the older functioning of sensory cortex. In language, in interpreting other people, in music and art, we often combine the sensory and the abstract into a single, seamless flow of experience.

This chapter takes as its target ‘ambitious physicalism’: an approach that aims to provide an explanatory reduction of consciousness to a physical and functional base. The chapter uses a range of cases involving the phenomenon of ‘blindsight’ to argue for the reality of phenomenal appearances of such a kind that cannot be accounted for by the standard physicalist theories, whether eliminativist, functionalist, or representationalist. It argues that the physicalist faces a dilemma: either denying the reality of phenomenal appearances by trying to identify those appearances with something manifest and describable in non-phenomenal terms, or facing an unavoidable arbitrariness in deciding which hidden features should be assigned metaphysically necessary and constitutive status with respect to conscious phenomena. The chapter argues that the cost of abandoning ambitious, reductive physicalism is not high, since we can still study the systematic relations between phenomenal appearances and physical conditions. The persistent failure to find an ultimate explanation of the real ‘nature’ of consciousness does not threaten the explanatory completeness of science.

Any system with the basic package is a decider; any decider with directly active perceptual information has the ‘basic package-plus’ and is a ‘decider-plus’. This chapter argues that being a decider-plus is logically sufficient for perceptual consciousness. First, on the provisional assumption that the basic package-plus includes all the purely functional conditions necessary for perceptual-phenomenal consciousness, the sole-pictures argument of Chapter 4 is extended to cover any decider-plus, not just zombies; then that assumption is defended. No merely natural or nomological or brute necessity has to be invoked. Among numerous likely objections discussed are those relating to blindsight; automatism; the usual objections to functionalist accounts of consciousness; the ‘explanatory gap’; and Carruthers’s critique of rival accounts to his own.

Sensory systems are automatic sorting machines which assign external sensed objects (distal stimuli) to classes on the basis of useful commonalities found in them. The results of a system=s sorting activities are made available to the perceiver in the form of a sensation, which can be held in memory or later recalled. Appearance thus follows classification as the record thereof. It follows (a) that sensory qualities are prior to experience and hence cannot be defined in terms of it, and (b) that all variations in the appearance of the stimulus are representationally significant (but not that all phenomenal variation is representationally significant).

Does ‘blindsight’ show that seeing is only inessentially an experience? The data is examined, and difficulties raised. Why always low‐key examples? How do we know it is not a borderline example of seeing (since they are theoretically guaranteed)? The argument pro the view that seeing occurs and experience does not is examined. The likelihood of these twin possibilities is counterbalanced against alternative interpretations of the data, and on the whole found wanting. But assuming that they are both realized, what theoretical account of seeing is open to one? That it is a cerebral phenomenon endowed with suitable input and output causal properties? But is this a statement of real essence? If so, it is not a viable theory. Presumably, it is a functionalist statement of nominal essence. However, while seeing has necessary origin properties, the cognitive effects of seeing are inessential. Then why believe that ‘seeing’ names any phenomenon at all? And why neglect its actual experiential function? The conclusion is that the experiential status of seeing is part of its essence, and that the standard interpretation of ‘blindsight’ is tantamount to jettisoning the very concept.

In this chapter, recent fMRI studies of activity in the ventral and dorsal streams of Dee Fletcher and other individuals with visual deficits are discussed. The results of neuroimaging studies of visual form agnosia, optic ataxia, and other disorders converge nicely with the earlier behavioural work discussed earlier chapters. We learn about ‘blindsight’, spared visual abilities in patients with large lesions of primary visual cortex.

Contra sense datum theories, most philosophers hold that perceptions have immediate ‘objective import'. How should the possession by a perception of such import be explained? The paper suggests that two important dimensions along which accounts of perceptual objectivity divide turn on answers to the following questions. (1) The Division of Labour Question: should the full content of our commonsense realism about the world we perceive be thought of as part of the actual content of perception itself or something the theorist of perception assumes? (2) The Consciousness Question: is it possible to derive explanations of the objectivity of conscious perceptions from an account of the objectivity possessed by non-conscious perceptions? The paper argues that a relational theory of perceptual consciousness delivers a negative answer (with Burge and contra Strawson) to the first, and a negative answer(with Strawson and contra Burge) to the second, exploiting the key insights in each of these philosophers approaches.

This chapter shows that blindsight illustrates that at least a limited analysis of visual signals continues in some patients even in those parts of their visual field for which they are subjectively blind. It begins by presenting categories of residual visual capacities. There are two general approaches to indirect methods of testing for residual visual function that allow an inference without requiring the subject to guess ‘without seeing’: (1) reflexes to visual stimuli in the blind hemifield; (2) interactions between the intact and impaired hemifields. There can be no doubt that parallel extrastriate visual pathways can mediate visual discriminations, in humans as well as in other primates, but it is the dissociations that emerge, suggesting a segregation of functions, that we are only beginning to characterize.

Typically, those types of damages which cause serious loss of mental and physical capacities are what most people associate with brain damage. Surprisingly, in virtually all of the major cognitive categories that are disturbed by brain damage, there can be remarkably preserved functioning – without the patients themselves being aware of this. Examples of this ‘performance without awareness’ is the severe themory disorder known as amnesic syndrome and the phenomenon of blindsight, in which patients can make visual discriminations even though they are ‘blind’ as a result of damage to the visual cortex of the brain. This chapter attempts to give an indication of the type of evidence that exists for residual, so-called implicit, processing. The chapter concentrates on amnesia and blindsight. The chapter focuses on neural pathways and visual attributes on the former and the nature of the psychological disorder and patients’ commentaries on the latter.

Disentangling deficits by dissociations, and the constructing of hypotheses about independence and hierarchical structure, is the very meat of day-to-day neuropsychological analysis and theorizing. This chapter examines its importance in revealing aspects of mental structure that may not be easily seen in normal function. Further, the chapter explores how the various examples: blindsight, agnosia, aphasia, and neglect, are not only doubly dissociable but multiply dissociable and how each can occur as separate, isolated deficits that may demand theoretical speculation within its own domain.

This chapter is concerned with the most advanced state of cognition, consciousness. It reviews some of the classic studies of performance without awareness. For instance, it is now a well-known phenomenon in amnesic patients that they can often perform certain tasks very well, but they have no recollection of ever having done the task. By presenting part of the training stimuli, the performance of amnesic patients in recognition tasks can be improved markedly, a phenomenon which is now known as ‘priming’. The chapter describes a phenomenon was discovered which this chapter terms ‘blindsight’, where patients with extensive damage to their visual cortex nevertheless are able to respond to stimuli in their blind fields. Interestingly, a similar phenomenon has been found in monkeys with lesions to the striate cortex. This chapter discusses the implications of these and related phenomena for the understanding of consciousness.

Damage to the primary visual cortex can cause a profound loss of awareness of the visible world. However, surviving pathways appear to provide sufficient visual information to allow the brain to mediate a range of visual tasks in the absence of such awareness. In this chapter, the authors discuss how ‘blindsight’ should not be characterized as ‘unconscious perception’. Instead, it should be more correctly seen as a collection of residual visuomotor responses that may depend on a variety of relatively independent circuits in the superion colliculus and dorsal stream. Further, this chapter contends that ‘blindsight’ only becomes paradoxical if one regards vision as a unitary process. If it is accepted that the mechanisms capable of providing perceptual experience are separate from those underlying the visual control of action, the paradox disappears.

This chapter discusses some examples of neuropsychological defects in which awareness is disconnected from a capacity to discriminate or to remember or to attend or to read or to speak. Some of these are prosopagnosia, acquired dyslexia, aphasia, split-brain, and blindsight.