Conscious visual perception can fail in many circumstances. However, little is known about the causes and processes leading to failures of visual awareness. In this study, we introduce a new signal detection measure termed subjective discriminability of invisibility that allows one to distinguish between subjective blindness due to reduction of sensory signals or to lack of attentional access to sensory signals. The SDI is computed based upon subjective confidence in reporting the absence of a target . Using this new measure, (...) we found that target misses were subjectively indistinguishable from physical absence when contrast reduction, backward masking and flash suppression were used, whereas confidence was appropriately modulated when dual task, attentional blink and spatial uncertainty methods were employed. These results show that failure of visual perception can be identified as either a result of perceptual or attentional blindness depending on the circumstances under which visual awareness was impaired. (shrink)

Most contemporary theorists regard the traditional thesis that perception is essentially conscious as just another armchair edict to be abandoned in the wake of empirical discovery. Here I reconsider this dramatic departure from tradition. My aim is not to recapture our prelapsarian confidence that perception is inevitably conscious (though much I say might be recruited to that cause). Instead, I want to problematize the now ubiquitous belief in unconscious perception. The paper divides into two parts. Part One is more purely (...) philosophical. It explains how standard arguments for unconscious perception rely on contentious background assumptions concerning the relation between ordinary perception and the explanatory constructs of scientific psychology. Part Two, in contrast, offers detailed engagement with relevant empirical work. It exposes how, even setting aside the concerns identified in Part One, a dilemma confronts the believer in unconscious perception. This dilemma arises because ordinary perception is an individual-level state or occurrence, yet criteria sufficiently stringent to guarantee that a putatively perceptual state is unconscious vitiate the grounds for its attribution to the individual. The dilemma foments a hypothesis, namely that the conditions for genuine, individual-level perception are sufficient conditions for perceptual consciousness. The viability of this hypothesis should unnerve anyone who thinks unconscious perception is simply an empirical given. (shrink)

Block () highlights two experimental studies of neglect patients which, he contends, provide ‘dramatic evidence’ for unconscious seeing. In Block's hands this is the highly non-trivial thesis that seeing of the same fundamental kind as ordinary conscious seeing can occur outside of phenomenal consciousness. Block's case for it provides an excellent opportunity to consider a large body of research on clinical syndromes widely held to evidence unconscious perception. I begin by considering in detail the two studies of neglect to which (...) Block appeals. I show why their interpretation as evidence of unconscious seeing faces a series of local difficulties. I then explain how, even bracketing these issues, a long-standing but overlooked problem concerning our criterion for consciousness problematizes the appeal to both studies. I explain why this problem is especially pressing for Block given his view that phenomenal consciousness overflows access consciousness. I further show that it is epidemic—not only affecting all report-based studies of unconscious seeing in neglect, but also analogous studies of the condition most often alleged to show unconscious seeing, namely blindsight. (shrink)

People’s awareness of tactile stimuli has been investigated in far less detail than their awareness of stimuli in other sensory modalities. In an attempt to fill this gap, we provide an overview of studies that are pertinent to the topic of tactile consciousness. We discuss the results of research that has investigated phenomena such as “change blindness”, phantom limb sensations, and numerosity judgments in tactile perception, together with the results obtained from the study of patients affected by deficits that can (...) adversely affect tactile perception such as neglect, extinction, and numbsense. The similarities as well as some of the important differences that have emerged when visual and tactile conscious information processing have been compared using similar experimental procedures are highlighted. We suggest that conscious information processing in the tactile modality cannot be separated completely from the more general processing of spatial information in the brain. Finally, the importance of considering tactile consciousness within the larger framework of multisensory information processing is also discussed. (shrink)

The question of whether blindsight is a form of unconscious perception continues to spark fierce debate in philosophy and psychology. One side of the debate holds that while the visual information categorized in blindsight is not access-conscious, it is nonetheless a form of perception, albeit a form of unconscious perception. The opposition, by contrast, holds that blindsight is just a form of degraded conscious perception that makes the categorized information harder to access because it is degraded. In this chapter, we (...) address the opposition’s arguments for thinking that blindsight is a form of degraded conscious vision and then argue that the residual awareness found in blindsight is a form of non-perceptual awareness. To back this claim, we examine the residual visual abilities to detect and discriminate colour found in some blindsight patients and show that residual consciousness in blindsight is indirect and lacks the phenomenal character characteristic of conscious vision. (shrink)

Phillips argues that blindsight is due to response criterion artefacts under degraded conscious vision. His view provides alternative explanations for some studies, but may not work well when one considers several key findings in conjunction. Empirically, not all criterion effects are decidedly non-perceptual. Awareness is not completely abolished for some stimuli, in some patients. But in other cases, it was clearly impaired relative to the corresponding visual sensitivity. This relative dissociation is what makes blindsight so important and interesting.

This thesis has, as its primary target, the neo-cartesianism, or property dualism of certain philosophers of mind: David Chalmers, Tim Bayne, and others. All begin with a pre-theoretic commitment to the view that all perceptual states are conscious. They define consciousness by saying that it is synonymous with having ‘qualia’ – a term directed at phenomenal properties which defy reduction to physical states. The thesis argues that this position is challenged by certain neurological conditions, - blindsight, visual form agnosia etc- (...) which we can generalise as ‘dissociations’: conditions in which functions are separated from awareness. The thesis holds that these are examples of unconscious perception, which present the case for a different pre-theoretic position, and a redefinition of concepts used in the vicinity. Insofar as the neo-cartesians recognise the empirical, their inclination to reject the dissociations is challenged with new cases and paradigms which have emerged in recent years. It is contended that the dissociations disrupt Chalmers’ coherence between the phenomenal and the psychological, Bayne’s commitment to the Unity of Consciousness, and Phillips’ campaign against unconscious perception. In addition, synaesthesia is advanced as a problem case for Bayne’s unity contention. I argue that the dissociations are not easily dismissed, and present a real challenge for neo-cartesianism. In exploring this challenge, the thesis contributes to the case for a different philosophy of mind – a Higher Order Thought approach. The notion of unconscious perception – it is contended - much more easily finds an accommodation in HOT theories, so this thesis contributes to existing arguments for that position. HOT theories also have an advantage in being receptive to reduction, in giving a developmental account of consciousness, and in being more open to the accommodation of empirical discoveries. In each respect, there is an advantage over the respective positions taken by Chalmers and Bayne. (shrink)