Hill on phenomenal consciousness

I argue that it is at least open to a proponent of type materialism for phenomenal consciousness to accept Hill’s representational theory of experiential awareness of perceptual qualia.     

A global workspace model for phenomenal and access consciousness

Both the global workspace theory and Block’s distinction between phenomenal and access consciousness, are central in the current debates about consciousness and the neural correlates of consciousness. In this article, a unifying global workspace model for phenomenal and access consciousness is proposed. In the model, recurrent neural interactions take place in distinct yet interacting access and phenomenal brain loops. The effectiveness of feedback signaling onto sensory cortical maps is emphasized for the neural correlates of phenomenal consciousness. Two forms of top-down attention, attention for perception and attention for access, play differential roles for phenomenal and access consciousness. The model is implemented in a neural network form, with the simulation of single and multiple visual object processing, and of the attentional blink.     

Where experiences are: Dualist, physicalist, enactive and reflexive accounts of phenomenal consciousness

Dualists believe that experiences have neither location nor extension, while reductive and ‘non-reductive’ physicalists (biological naturalists) believe that experiences are really in the brain, producing an apparent impasse in current theories of mind. Enactive and reflexive models of perception try to resolve this impasse with a form of “externalism” that challenges the assumption that experiences must either be nowhere or in the brain. However, they are externalist in very different ways. Insofar as they locate experiences anywhere, enactive models locate conscious phenomenology in the dynamic interaction of organisms with the external world, and in some versions, they reduce conscious phenomenology to such interactions, in the hope that this will resolve the hard problem of consciousness. The reflexive model accepts that experiences of the world result from dynamic organism–environment interactions, but argues that such interactions are preconscious. While the resulting phenomenal world is a consequence of such interactions, it cannot be reduced to them. The reflexive model is externalist in its claim that this external phenomenal world, which we normally think of as the “physical world,” is literally outside the brain. Furthermore, there are no added conscious experiences of the external world inside the brain. In the present paper I present the case for the enactive and reflexive alternatives to more classical views and evaluate their consequences. I argue that, in closing the gap between the phenomenal world and what we normally think of as the physical world, the reflexive model resolves one facet of the hard problem of consciousness. Conversely, while enactive models have useful things to say about percept formation and representation, they fail to address the hard problem of consciousness.

Identifying neural correlates of consciousness: the state space approach

This article sketches an idealized strategy for the identification of neural correlates of consciousness. The proposed strategy is based on a state space approach originating from the analysis of dynamical systems. The article then focuses on one constituent of consciousness, phenomenal awareness. Several rudimentary requirements for the identification of neural correlates of phenomenal awareness are suggested. These requirements are related to empirical data on selective attention, on completely intrinsic selection and on globally unconscious states. As an example, neuroscientific findings on synchronized gamma activity are categorized according to these requirements.     

Same old, same old: the same-order representation theory of consciousness and the division of phenomenal labor

The same-order representation theory of consciousness holds that conscious mental states represent both the world and themselves. This complex representational structure is posited in part to avoid a powerful objection to the more traditional higher-order representation theory of consciousness. The objection contends that the higher-order theory fails to account for the intimate relationship that holds between conscious states and our awareness of them–the theory ‘divides the phenomenal labor’ in an illicit fashion. This ‘failure of intimacy’ is exposed by the possibility of misrepresentation by higher-order states. In this paper, I argue that despite appearances, the same-order theory fails to avoid the objection, and thus also has troubles with intimacy. A version of this paper was presented at the ‘Self-Representational Approaches to Consciousness’ conference, Center for Consciousness Studies, University of Arizona, March 18th–20th, 2005.     

Audiovisual phenomenal causality

We report three experiments in which visual or audiovisual displays depicted a surface (target) set into motion shortly after one or more events occurred. A visual motion was used as an initial event, followed directly either by the target motion or by one of three marker events: a collision sound, a blink of the target stimulus, or the blink together with the sound. The delay between the initial event and the onset of the target motion was varied systematically. The subjects had to rate the degree of perceived causality between these events. The results of the first experiment showed a systematic decline of causality judgments with an increasing time delay. Causality judgments increased when additional auditory or visual information marked the onset of the target motion. Visual blinks of the target and auditory clacks produced similar causality judgments. The second experiment tested several models of audiovisual causal processing by varying the position of the sound within the visual delay period. No systematic effect of the sound position occurred. The third experiment showed a subjective shortening of delays filled by a clack sound, as compared with unfilled delays. However, this shortening cannot fully explain the increased tolerance for delays containing the clack sound. Taken together, the results are consistent with the interpretation that the main source of the causality judgments in our experiments is the impression of a plausible unitary event and that perfect synchrony is not necessary in this case.     

Physicalism and phenomenal concepts

Frank Jackson’s famous Knowledge Argument moves from the premise that complete physical knowledge is not complete knowledge about experiences to the falsity of physicalism. In recent years, a consensus has emerged that the credibility of this and other well-known anti-physicalist arguments can be undermined by allowing that we possess a special category of concepts of experiences, phenomenal concepts, which are conceptually independent from physical/functional concepts. It is held by a large number of philosophers that since the conceptual independence of phenomenal concepts does not imply the metaphysical independence of phenomenal properties, physicalism is safe. This paper distinguishes between two versions of this novel physicalist strategy—Phenomenal Concept Strategy (PCS)—depending on how it cashes out “conceptual independence,” and argues that neither helps the physicalist cause. A dilemma for PCS arises: cashing out “conceptual independence” in a way compatible with physicalism requires abandoning some manifest phenomenological intuitions, and cashing it out in a way compatible with those intuitions requires dropping physicalism. The upshot is that contra Brian Loar and others, one cannot “have it both ways.”     

Lines that induce phenomenal transparency

Three neighbouring opaque surfaces may appear split into two layers, one transparent and one opaque beneath, if an outline contour is drawn that encompasses two of them. The phenomenon was originally observed by Kanizsa [1955 Rivista di Psicologia 69 3-19; 1979 Organization in Vision: Essays on Gestalt Psychology (New York: Praeger)], for the case where an outline contour is drawn to encompass one of the two parts of a bicoloured figure and a portion of a background of lightest (or darkest) luminance. Preliminary observations revealed that the outline contour yields different effects: in addition to the stratification into layers described by Kanizsa, a second split, opposite in depth order, may occur when the outline contour is close in luminance to one of the three surfaces. An initial experiment was designed to investigate what conditions give rise to the two phenomenal transparencies: this led to the conclusion that an outline contour superimposed on an opaque surface causes this surface to emerge as a transparent layer when the luminances of the contour and the surface differ, in absolute value, by no more than 13.2 cd m(-2). We have named this phenomenon 'transparency of the intercepted surface', to distinguish it from the phenomenal transparency arising when the contour and surface are very different in luminance. When such a difference exists, the contour acts as a factor of surface definition and grouping: the portion of the homogeneous surface it bounds emerges as a fourth surface and groups with a nearby surface if there is one close in luminance. The transparency phenomena ('transparency of the contoured surface') perceived in this context conform to the constraints of Metelli's model, as demonstrated by a second experiment, designed to gather 'opacity' ratings of stimuli. The observer judgments conformed to the values predicted by Metelli's formula for perceived degree of transparency, alpha. The role of the outline contour in conveying figural and intensity information is discussed.     

Apparent movement in phenomenal space

The spatial and temporal variables in Korte’s third law of apparent movement were studied in pictorial arrays in which size constancy could be expected to prevail. The thresholds for apparent movement were determined under conditions in which two squares appeared on a plane either with or without perspective information for depth. The results suggest that apparent movement varies with the perceived depth separation only if the size of the stimulus pair is congruent with contextual depth representations. The obtained psychophysical function relating thresholds for third-dimensional movement to pictorial depth scale supports the view that apparent movement preserves gradient-of-texture information.     

The limits of perceptual phenomenal content

Philosophical Studies - There is an ongoing debate in philosophy of mind and epistemology about whether perceptual experience only represents those “thin” features of our environment...     

A connectionist theory of phenomenal experience

When cognitive scientists apply computational theory to the problem of phenomenal consciousness, as many have been doing recently, there are two fundamentally distinct approaches available. Consciousness is to be explained either in terms of the nature of the representational vehicles the brain deploys or in terms of the computational processes defined over these vehicles. We call versions of these two approaches vehicle and process theories of consciousness, respectively. However, although there may be space for vehicle theories of consciousness in cognitive science, they are relatively rare. This is because of the influence exerted, on the one hand, by a large body of research that purports to show that the explicit representation of information in the brain and conscious experience are dissociable, and on the other, by the classical computational theory of mind--the theory that takes human cognition to be a species of symbol manipulation. Two recent developments in cognitive science combine to suggest that a reappraisal of this situation is in order. First, a number of theorists have recently been highly critical of the experimental methodologies used in the dissociation studies--so critical, in fact, that it is no longer reasonable to assume that the dissociability of conscious experience and explicit representation has been adequately demonstrated. Second, classicism, as a theory of human cognition, is no longer as dominant in cognitive science as it once was. It now has a lively competitor in the form of connectionism; and connectionism, unlike classicism, does have the computational resources to support a robust vehicle theory of consciousness. In this target article we develop and defend this connectionist vehicle theory of consciousness. It takes the form of the following simple empirical hypothesis: phenomenal experience consists of the explicit representation of information in neurally realized parallel distributed processing (PDP) networks. This hypothesis leads us to reassess some common wisdom about consciousness, but, we argue, in fruitful and ultimately plausible ways.     

Presentism,eternalism, and phenomenal change

Normally, when we notice a change taking place, our conscious experience has a corresponding quality of phenomenal change. Here it is argued that one’s experience can have this quality at or during a time when there is no change in which phenomenal properties one instantiates. This undermines a number of otherwise forceful arguments against leading metaphysical theories of change, but also requires these theories to construe change as a secondary quality, akin to color.     

Segmentation, attention and phenomenal visual objects

Issues concerning selective attention provoke new questions about visual segmentation, and vice-versa. We illustrate this by describing our recent work on grouping under conditions of inattention, on change blindness for background events and the residual processing of undetected background changes, on modal versus amodal completion in visual search, and the differential effects of these two forms of completion on attentional processes, and on attentional modulation of lateral interactions thought to arise in early visual cortex. Many of these results indicate that segmentation processes substantially constrain attentional processes, but the reverse influence is also apparent, suggesting an interactive architecture. We discuss how the 'proto-objects' revealed by studies of segmentation and attention (i.e. the segmented perceptual units which constrain selectivity) may relate to other object-based notions in cognitive science, and we wrestle with their relation to phenomenal visual awareness.