Luminance and edge information in grouping: A study using visual search.

Abstract

Preattentive grouping is supported by 2 systems, a brightness system that is contrast polarity sensitive and an edge system that is relatively insensitive to contrast polarity. Search was spatially parallel for pairs of same contrast polarity vertically aligned circles, among horizontal pairs, and serial for pairs of circles that had the opposite contrast polarity (Experiments 1-3). By replacing the circles with squares, the authors investigated the effect of adding collinear edge information. When collinear edges were present, the polarity difference between paired items did not disrupt grouping (Experiments 4-6). These results support models of grouping in which brightness and edge information are processed separately (e.g., S. Grossberg & E. Mingolla, 1985) and models of visual search in which complex relations between stimuli can be computed in parallel across the display.

Visual search in Alzheimer’s disease: a deficiency in processing conjunctions of features

“…The results from such studies imply that there is not a strict dichotomy between automatic and attention-related visual processing, but rather a continuum. In addition, the need for attention also appears to be dependent upon the outcome and efficiency of other aspects of visual processing such as stimulus similarity, stimulus dimensions, the ability to group and segment; the ability of the visual system to use visual information extracted pre-attentively to guide shifts of attention during search, the inherent noise in visual processing and other low-level factors [15,18].…”

“…This forms a type of efficient conjunction search in which strategies based on early visual processing, such as perceptual segmentation and grouping, can be employed in order to reduce the need for the serial application of attention [11,15,18,43]. In this task, the target, a black vertical bar, was surrounded by distractors composed of black horizontal bars and white vertical bars.…”

3-D constraints on spatially parallel shape perception

“…In this last condition targets and distractors had the same local orientations as in the first condition, so the parallel search functions found with closed shapes cannot be attributed to this factor. Instead, it appears that spatially parallel binding operated using display properties such as collinearity and closure (see also Donnelly et aI., 1998, Elder & Zucker, 1993, and Gilchrist, Humphreys, Riddoch, & Neumann, 1997, for further evidence on the spatially parallel computation of closure and collinearity, respectively). Nor is it the case that grouping between form elements only gives rise to 2-D descriptions of displays.…”

Non-transient luminance changes do not capture attention

“…On half of the trials, the luminance cue changed from black to white, whilst on the other half it changed from white to black, with both occurring against a mid-grey background. This manipulation was motivated by a number of studies that have shown an interaction between luminance contrast and luminance polarity (Aks & Enns, 1992;Enns, Austen, Di Lollo, Rauschenberger, & Yantis, 2001;Gilchrist, Humphreys, Riddoch, & Neumann, 1997;Sutter, Beck, & Graham, 1989). Specifically, these studies have revealed that sensitivity to differences in luminance contrast is increased when the change is accompanied by a reversal in polarity.…”