Segmentation by single and combined features involves different contextual influences

Alberti, C. F., Pavan, A., Campana, G. and Casco, C. (2010) Segmentation by single and combined features involves different contextual influences. Vision Research, 50 (11). pp. 1065-1073. ISSN 00426989

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Orientation discrimination of a texture line having orientation different from that of static background lines is facilitated when the lines are aligned along their orientation axis and when their separation is small (Experiment 1a). The facilitation by alignment remains when motion is added to the target (Experiment 1b). However, when the motion rather than the orientation has to be judged, alignment reduces sensitivity (d') regardless of whether the target has orientation the same as (iso-oriented) or different from background elements (Experiment 2). The inhibitory effect of alignment is confirmed when subjects have to discriminate the motion direction of an iso-oriented target (Experiment 3). Such inhibition by alignment is stronger when elements are close and may reflect a property of lateral interactions of motion detectors, since it is only present when observers have to judge the target motion direction. Overall, our results indicate an opposite role of the lateral interactions that facilitate grouping of iso-oriented and collinear elements, in segmentation by orientation contrast and motion contrast. In other words, global grouping (i) facilitates discrimination of orientation contrast, indicating a global process, and (ii) inhibits both detection and discrimination of motion contrast, suggesting the presence of a local process. © 2010 Elsevier Ltd.

Keywords:article, controlled study, human, human experiment, image analysis, movement perception, observation, orienting response, pattern recognition, priority journal, psychometry, stimulus response, task performance, visual discrimination, visual orientation, visual stimulation, visual threshold, Contrast Sensitivity, Discrimination (Psychology), Humans, Motion Perception, Orientation, Photic Stimulation, Psychometrics, Sensory Thresholds
Subjects:C Biological Sciences > C800 Psychology
Divisions:College of Social Science > School of Psychology
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ID Code:15498
Deposited On:21 Oct 2014 14:49

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