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Parallel and serial grouping of image elements in visual perception.

Publication Type:

Journal Article

Source:

Journal of experimental psychology. Human perception and performance, Volume 36, Number 6, p.1443–59 (2010)

URL:

http://psycnet.apa.org/journals/xhp/36/6/1443/

Keywords:

Adult, Association Learning, Attention, Color Perception, Discrimination Learning, Female, Gestalt Theory, Humans, Male, Orientation, Pattern Recognition, Serial Learning, Visual, Young Adult

Abstract:

The visual system groups image elements that belong to an object and segregates them from other objects and the background. Important cues for this grouping process are the Gestalt criteria, and most theories propose that these are applied in parallel across the visual scene. Here, we find that Gestalt grouping can indeed occur in parallel in some situations, but we demonstrate that there are also situations where Gestalt grouping becomes serial. We observe substantial time delays when image elements have to be grouped indirectly through a chain of local groupings. We call this chaining process incremental grouping and demonstrate that it can occur for only a single object at a time. We suggest that incremental grouping requires the gradual spread of object-based attention so that eventually all the object's parts become grouped explicitly by an attentional labeling process. Our findings inspire a new incremental grouping theory that relates the parallel, local grouping process to feedforward processing and the serial, incremental grouping process to recurrent processing in the visual cortex.

Lateral interactions among membrane proteins. Implications for the organization of gap junctions.

Publication Type:

Journal Article

Source:

Biophysical journal, Volume 52, Number 3, p.441–54 (1987)

URL:

http://www.cell.com/biophysj/abstract/S0006-3495(87)83233-2

Keywords:

Animals, Biological, Electron, Freeze Fracturing, Intercellular Junctions, Intercellular Junctions: ultrastructure, Liver, Liver: metabolism, Liver: ultrastructure, Mathematics, Membrane Proteins, Membrane Proteins: metabolism, Mice, Microscopy, Models, Protein Conformation

Abstract:

We have studied the relationship between interprotein forces and the lateral distribution of proteins in disordered mouse liver gap junctions. Data on protein positions are obtained from freeze-fracture electron micrographs. Short-ranged correlations in observed positions are characteristic of interacting particles in a fluid state. An analysis derived from statistical mechanics allows the determination of the magnitude and functional form of interprotein forces. We find that jap junction proteins are mutually repulsive, in a manner consistent with electrostatics and excluded volume. This dictates that long-ranged protein aggregation into jap junction plaques cannot arise solely from interparticle interactions. An alternative is the balance of lateral pressures between the junction and the surrounding glycocalyx. This idea is quantified into a model. Junctional pressure arises from protein-protein interactions and is computed from a pressure equation based on the force and a radial distribution function describing order. The pressure from the glycocalyx is assumed to arise from mixing, electrostatic, and elastic interactions of sugar residues, and is described with terms from Flory-Krigbaum and McMillan-Mayer theories. The results of this modeling are in reasonable agreement with available experimental data.

Visual attention and perceptual grouping.

Publication Type:

Journal Article

Source:

Perception & psychophysics, Volume 52, Number 3, p.277–94 (1992)

URL:

http://www.springerlink.com/content/733797016m810476/

Keywords:

Attention, Discrimination Learning, Humans, Orientation, Pattern Recognition, Perceptual Masking, Psychophysics, Visual

Abstract:

Perceptual organization is thought to involve an analysis of both textural discontinuities and perceptual grouping. In earlier work, we found that textural discontinuities were detected normally even when visual attention was engaged elsewhere. Here we report how perceptual grouping is affected when visual attention is engaged by a concurrent visual task. To elicit perceptual grouping, we used the Gestalt demonstrations of grouping on the basis of proximity and of similarity. Four tasks were investigated, some requiring the observer to discriminate between horizontal and vertical grouping, and some requiring the observer to merely detect the presence or absence of grouping. Visual attention was engaged at the center of the display by a form identification task. The detection of a textural discontinuity served as a control task. Concurrent form identification conflicted with all four grouping tasks, resulting in a significant reduction of grouping performance in each case. No performance reduction was observed when either form identification or grouping discrimination was combined with the detection of a textural discontinuity. These results suggest that perceptual grouping and form identification compete for visual attention, whereas the detection of a textural discontinuity does not.

Attention and awareness.

Publication Type:

Book Chapter

Authors:

Braun, Jochen

Source:

Oxford Companion to Consciousness, Oxford University Press USA (2009)

ISBN:

0198569513

It's great but not necessarily about attention.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Psyche: An Interdisciplinary Journal of Research on Consciousness, Australia: Assn for the Scientific Study of Consciousness, Volume 7, Number 6, p.No Pagination Specified (2001)

URL:

http://theassc.org/files/assc/2500.pdf

Keywords:

Attention, comment, perception

Abstract:

Comments on an extensive research program surrounding a phenomenon called inattentional blindness reported by A. Mack and I. Rock (see record <RelatedUID>1998-07464-000</RelatedUID>) in their book of the same name. The general conclusion that is drawn from the work is that no conscious perception can occur without attention. The author of this comment points out that Mack and Rock manipulated both expectation and attention and suggests that their results ("inattentional blindness') may have been caused by lack of expectation rather than lack of attention. This alternative reading of Mack and Rock's results is supported by other findings, which suggest that "pure' manipulations of expectation produce "blindness' whereas "pure' manipulations of attention do not. The author believes that the human visual system may use natural and acquired "priors' to solve the probabilistic problem of perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)

Natural scenes upset the visual applecart.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Trends in cognitive sciences, Volume 7, Number 1, p.7–9 (2003)

URL:

http://www.sciencedirect.com/science/article/pii/S1364661302000086

Abstract:

The effortless ease of everyday vision seems to contradict numerous findings on the limited capacity of visual attention. However, natural scenes appear to escape the stringent limitations of attention that apply to seemingly far simpler stimuli. This astonishing result will oblige us to rethink the nature of visual attention and its limited capacity.

On the detection of salient contours.

Publication Type:

Journal Article

Authors:

Braun, Jochen

Source:

Spatial vision, Volume 12, Number 2, p.211–25 (1999)

URL:

http://www.ingentaconnect.com/content/vsp/spv/1999/00000012/00000002/art00006?token=0056191b23dca0ac57e41225f40386f2c4b41567d766725506e576b3427656c3c6a333f25662e5031d71b0

Keywords:

Computer Simulation, Form Perception, Form Perception: physiology, Humans, Models, Observer Variation, Theoretical, Visual Cortex, Visual Cortex: physiology

Abstract:

When visual space is densely populated by elements of random orientation, elements which happen to be aligned may form a perceptually salient 'contour' (Field et al., 1993; Kovacs and Julesz, 1993). Here we further characterize human performance for detecting this type of Gestalt grouping. We find that detectability of salient contours reaches a plateau when they comprise at least 10 elements and are presented for at least 200 ms. It has been suggested that the detection of salient contours is mediated by the intrinsic connectivity of striate cortex and several computational models have been formulated on this basis. The present data provide a benchmark against which such models can be evaluated.

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