Abstract: Visual percepts frequently appear chromatically rich, yet their paucity in reportable information has led to widely accepted minimalist models of vision. The discrepancy may be resolved by positing that the richness of natural scenes is reflected in phenomenal consciousness but not in detail in the phenomenal judgments upon which reports about qualia are based. Conceptual awareness (including phenomenal judgments) arises from neural mechanisms that categorize objects, and also from mechanisms that conceptually characterize textural properties of pre-categorically segmented regions in the visual field. Experimental evidence suggests that complex images instigate the generation of so-called ensemble phenomenal judgments. These involve concepts that categorize global attributes of segmented areas but carry no information pertaining to details. It is then argued that there are cogent reasons for believing that phenomenal percepts (i.e. qualia) arising from chromatically complex stimuli cohere in this ensemble sense with both the stimulus and with the resulting ensemble phenomenal judgments. Thus, spatially detailed retinal images are deemed to yield correspondingly detailed phenomenal experiences that are in turn conceptually apprehended via a relatively small number of ensemble phenomenal judgments. Lastly, it is suggested that the bridge locus for chromatically rich phenomenal experiences is most plausibly located early in the cortical visual pathway

Abstract: This new edition uses the technique of visual masking to explore temporal aspects of conscious and unconscious processes down to a resolution in the...

Abstract: Durgin's (2002) commentary on our article provides us with an opportunity to look more closely at the relationship between information processing and consciousness. In our article we contrasted the information processing approach to interpreting our data, with our own 'scientific' approach to consciousness. However, we should point out that, on our view, information processing as a methodology is not by itself in conflict with the scientific study of consciousness - indeed, we have adopted this very methodology in our experiments, which we purport to use to investigate consciousness. Furthermore, Durgin's own review of the history of research on metacontrast (Lachter & Durgin, 1999) shows that some researchers investigating metacontrast also thought that they were in the business of evaluating the role of consciousness in accounting for their effects. Yet, there is no doubt that metacontrast research is a paradigm case of research generated from an information processing perspective. So, prima facie, investigating consciousness and using information processing methodology are compatible

Abstract: One of the biggest challenges in understanding perception is to understand how the nervous system manages to integrate the multiple codes it uses to represent features in multiple sensory modalities. From different cortical areas, which might separately register the sight of something red and the touch of something smooth, one effortlessly generates the perception of one thing that is both red and smooth. This process has been variously called "feature integration", "binding", or "synthesis". Citing some current models and some historical precursors, this paper makes some simple observations about the logic of feature integration. I suggest that "feature conjunction" is not strictly speaking conjunction at all, but rather joint predication; and that the critical task in "binding" is not simply grouping scattered representations together, or providing them a common label, but rather identifying those that have a common subject matter-those that are

Abstract: One of the things you learn if you read books and articles in (or about) cognitive science is that the brain does a lot of "filling in"--not filling in, but "filling in"--in scare quotes. My claim today will be that this way of talking is not a safe bit of shorthand, or an innocent bit of temporizing, but a source of deep confusion and error. The phenomena described in terms of "filling in" are real, surprising, and theoretically important, but it is a mistake to conceive of them as instances of something being filled in, for that vivid phrase always suggests too much--sometimes a little too much, but often a lot too much. Here are some examples (my boldface throughout)

Abstract: Advances in neuroanatomy and neurophysiology have called attention to reentrant signalling as the predominant form of communication between brain areas. We propose that explicit use be made of reentrant processing in theories of perception. To show that this can be done effectively in one domain, we report on a series of psychophysical experiments involving a new form of masking, which defies explanation by current feed-forward theories. This masking occurs when a brief display of target plus mask is continued with the mask alone. We report evidence of two masking processes: an early process affected by physical factors such as adapting luminance and contour proximity, and a later process affected by attentional factors such as set size, target pop-out, and spatial pre-cuing. We call this later process masking by

Abstract: Correspondence should be addressed to David A. Leopold david.leopold@tuebingen.mpg.deDuring the viewing of certain patterns, widely known as ambiguous or puzzle figures, perception lapses into a sequence of spontaneous alternations, switching every few seconds between two or more visual interpretations of the stimulus. Although their nature and origin remain topics of debate, these stochastic switches are generally thought to be the automatic and inevitable consequence of viewing a pattern without a unique solution. We report here that in humans such perceptual alternations can be slowed, and even brought to a standstill, if the visual stimulus is periodically removed from view. We also show, with a visual illusion, that this stabilizing effect hinges on perceptual disappearance rather than on actual removal of the stimulus. These findings indicate that uninterrupted subjective perception of an ambiguous pattern is required for the initiation of the brain-state changes underlying multistable vision.Visual perception involves coordination between sensory sampling of the world and active interpretation of the sensory data. Human perception of objects and scenes is normally stable and robust, but it falters when one is presented with patterns that are inherently ambiguous or contradictory. Under such conditions, vision lapses into a chain of continually alternating percepts, whereby a viable visual interpretation dominates for a few seconds and is then replaced by a rival interpretation. This multistable vision, or 'multistability', is thought to result from destabilization of fundamental visual mechanisms, and has offered valuable insights into how sensory patterns are actively organized and interpreted in the brain1, 2. Despite a great deal of recent research and interest in multistable perception, however, its neurophysiological underpinnings remain poorly understood. Physiological studies have suggested that disambiguation of ambiguous patterns

Abstract: High figure-ground contrast usually results in more positive evaluations of visual stimuli. This may either reflect that high figure-ground contrast per se is a desirable attribute or that this attribute facilitates fluent processing. In the latter case, the influence of high figure-ground contrast should be most pronounced under short exposure times, that is, under conditions where the facilitative influence on perceptual fluency is most pronounced. Supporting this hypothesis, ratings of the prettiness of visual stimuli increased with figure-ground contrast under short exposure times (.3, 1, and 3 seconds, respectively). This positive influence of figure-ground contrast was eliminated under an exposure time of 10 seconds. We conclude that stimuli with high figure-ground contrast are more appealing because they are easier to process, not because high figure-ground contrast per se is a desirable attribute. We discuss this finding in the context of William James? notion that the fringe of consciousness includes vague contextual feelings at the periphery of the focus of attention and suggest that perceptual fluency is one of these feelings

Abstract: The issue of capacity limits in visual short-term memory (VSTM) has been an area of active research since the 19th Century (Cattell, 1886). A common metaphor suggests that VSTM is akin to a limited capacity urn, able to hold only three-to-six items (Cowan, 2001). The 11 experiments in this thesis explore implications of this metaphor. Experiments 1-4 suggest that items in VSTM are not stored as coherent objects, contrary to recent suggestions (Luck & Vogel, 1997; Vogel, Woodman, & Luck, 2001). Experiments 5-6 contrast two distinct experimental techniques used to probe the structure of information encoded in VSTM. The "single-shot" technique measures sensitivity to differences across two sequential arrays (Luck & Vogel, 1997); the "flicker" technique measures response times to the detection of change, across multiple successive presentations of two alternate displays (Rensink, O'Regan, & Clark, 1997). It is shown that observers' underlying sensitivity to change, and by implication the structure of information encoded, is the same for these two techniques. Experiments 7-9 examine the relationship between observers' performance for detection and identification of change between two successive visual arrays. It is demonstrated that this relationship fails to meet basic assumptions inherent in the urn metaphor. An alternate model is proposed, which suggests that the capacity limit in VSTM is not determined by the number of items stored, but by the amount of information able to be extracted from a visual display. In Experiments 10-11, this alternative model is used to examine the short-term storage of visual information. Overall, the findings of the thesis are inconsistent with a model in which limits in the detection and identification of change are the result of a single process, which operates on a limited number of coherent objects held in a high-level memory store.