Online research in philosophy

This paper defends a novel account of how we introspect phenomenal states, the Demonstrative Attention account (DA). First, I present a set of necessary and sufficient conditions for phenomenal state introspection which are not psychological, but purely metaphysical and semantic. Next, to explain how these conditions can be satisfied, I describe how demonstrative reference to a phenomenal content can be achieved through attention alone. This sort of introspective demonstration differs from perceptual demonstration in being non-causal. DA nicely explains key intuitions about phenomenal self-knowledge, makes possible an appealing diagnosis of blindsight cases, and yields a highly plausible view as to the extent of our first-person epistemic privilege. Because these virtues stem from construing phenomenal properties as non-relational features of states, my defense of DA constitutes a challenge to relational construals of phenomenal properties, including functionalism and representationalism. And I provide reason to doubt that they can meet this challenge.

The phenomenal properties of conscious mental states happen to be exclusively accessible from the first-person perspective. Consequently, some philosophers consider their existence to be incompatible with materialist metaphysics. In this paper I criticise one particular argument that is based on the idea that for something to be real it must (at least in principle) be accessible from an intersubjective perspective. I argue that the exclusively subjective access to phenomenal contents can be explained by the very particular nature of the epistemological relation holding between a subject and his own mental states. Accordingly, this subjectivity does not compel us to deny the possibility that phenomenal contents are ontologically objective properties. First, I present the general form of the argument that I will discuss. Second, I show that this argument makes use of a criterion of reality that is not applicable to the case of subjective experience. Third, I discuss a plausible objection and give an argument for rejecting observation models of self-knowledge of phenomenal contents. These models fall prey to the homunculus illusion.

As far as an adequate understanding of phenomenal consciousness is concerned, representationalist theories of mind which are modelled on the information processing paradigm, are, as much as corresponding neurobiological or functionalist theories, confronted with a series of arguments based on inverted or absent qualia considerations. These considerations display the following pattern: assuming we had complete knowledge about the neural and functional states which subserve the occurrence of phenomenal consciousness, would it not still be conceivable that these neural states (or states with the same causal r.

By themselves, mesencephalic subcortical mechanisms provide a preattentive kind of consciousness, related to stimulus-related, short-latency dopamine release triggered by collicular input. Elaborate forms of consciousness, containing identifiable objects (visual, auditory, tactile, or chemical), imply longer-lasting phenomena that depend on the activation of prosencephalic networks. Nevertheless, the maintenance of these higher-level networks strongly depends on long-lasting mesencephalic dopamine release. (Published Online May 1 2007).

It has generally been assumed that rapid visual search is based on simple features and that spatial relations between features are irrelevant for this task. Seven experiments involving search for line drawings contradict this assumption; a major determinant of search is the presence of line junctions. Arrow- and Y-junctions were detected rapidly in isolation and when they were embedded in drawings of rectangular polyhedra. Search for T-junctions was considerably slower. Drawings containing T-junctions often gave rise to very slow search even when distinguishing arrow- or Y-junctions were present. This sensitivity to line relations suggests that preattentive processes can extract 3-dimensional orientation from line drawings. A computational model is outlined for how this may be accomplished in early human vision.

A standard view in philosophy of mind is that qualia and phenomenal character require consciousness. This paper argues that various experimental and clinical phenomena can be better explained if we reject this assumption. States found in early visual processing can possess qualitative character even though they are not in any sense conscious mental states. This non-standard interpretation bears the burden of explaining what must be added to states that have qualitative character in order to yield states of sensory awareness or sensory experience. I argue that the study of selective attention reveals resources that can be useful in that project. Two traditional objects are briefly considered.

The perception of the lightness of surfaces has been shown to be affected by information about the spatial configuration of those surfaces and their illuminants. For example, two surfaces of equal luminance can appear to be of very different lightness if one of the two appears to lie in a shadow. How are we to understand the character of the processes that integrate such spatial configuration information so as to yield the eventual appearance of lightness? This paper makes some simple observations about the vocabulary of appearance used in these contexts, and proposes that the end results can be called "phenomenal" in a traditional sense of that word. Processes whose products are phenomenal are next distinguished from processes characterized in other terms: (a) processes of perceptual grouping; (b) processes of perceptual organization; and (c) attentional (as opposed to preattentive) processes. These four categories are conceptually and empirically distinct. In particular, the paper reviews some evidence that appearances as of contours, occlusion, and amodally completed shapes can occur preattentively. Some implications for understanding gestalt grouping processes are briefly discussed.

Theories of human vision have generally assumed that the features underlying visual search and texture segmentation correspond to simple measurements made at the first stages of visual processing. In this paper, we describe a series of visual search experiments that refute this assumption. Using several variants of the Mueller-Lyer figure, we show that an illusion of length exists in preattentive vision -- search is easy when items contain line segments of equal length, but becomes difficult when these segments are adjusted to have the same apparent length. This illusion cannot be reduced by selective inhibition of features, such as that used to facilitate the rapid detection of feature conjunctions. For example, subjects are unable to ignore the wings when making judgements of the test line, even when it is advantageous to do so. This rules out explanations based on interactions among the features themselves. We also show that spatial filtering cannot account for this illusion, since these effects are indifferent to the sign of contrast of the line segments and can occur for textured lines having the same first-order statistics. The illusion, however, can be explained by a model in which line length is determined via grouping operations acting at a level prior to the formation of preattentive features.

Recent studies have shown that several scene-based properties can be determined rapidly and in parallel at preattentive levels, including surface convexity and concavity (Ramachandran, 1988), direction of illumination (Enns & Rensink, 1990), and three-dimensional orientation (Enns & Rensink, 1991). We show that in addition to these properties, preattentive vision is also sensitive to scene structure defined by shadows.

Recent work in experimental psychology and neuroscience has revealed a rather surprising architecture for early (or preattentive) perceptual processes. This paper will describe some of the surprising features of that architecture, and how they bear on recent philosophical debates about the notion of phenomenal consciousness. I will argue that the common sense idea that states of phenomenal consciousness are states of a unitary kind cannot survive confrontation with the details of how our early perceptual processing works. In particular, that architecture forces us to contemplate the prospect of phenomenal consciousness being sundered in two, with states that have phenomenal character making an appearance far before the arrival of anything one could call consciousness or awareness.