| Continuity-based and discontinuity-based segmentation in transparent and spatially segregated global motion. | |
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MedLine Citation:
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PMID: 10738070 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The mechanisms underlying the parsing of a spatial distribution of velocity vectors into two adjacent (spatially segregated) or overlapping (transparent) motion surfaces were examined using random dot kinematograms. Parsing might occur using either of two principles. Surfaces might be defined on the basis of similarity of motion vectors and then sharp perceptual boundaries drawn between different surfaces (continuity-based segmentation). Alternatively, detection of a high gradient of direction or speed separating the motion surfaces might drive the process (discontinuity-based segmentation). To establish which method is used, we examined the effect of blurring the motion direction gradient. In the case of a sharp direction gradient, each dot had one of two directions differing by 135 degrees. With a shallow gradient, most dots had one of two directions but the directions of the remainder spanned the range between one motion-defined surface and the other. In the spatial segregation case the gradient defined a central boundary separating two regions. In the transparent version the dots were randomly positioned. In both cases all dots moved with the same speed and existed for only two frames before being randomly replaced. The ability of observers to parse the motion distribution was measured in terms of their ability to discriminate the direction of one of the two surfaces. Performance was hardly affected by spreading the gradient over at least 25% of the dots (corresponding to a 1 degrees strip in the segregation case). We conclude that detection of sharp velocity gradients is not necessary for distinguishing different motion surfaces. |
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Authors:
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A T Smith; W Curran |
Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Vision research Volume: 40 ISSN: 0042-6989 ISO Abbreviation: Vision Res. Publication Date: 2000 |
Date Detail:
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Created Date: 2000-08-04 Completed Date: 2000-08-04 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 0417402 Medline TA: Vision Res Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 1115-23 Citation Subset: IM; S |
Affiliation:
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Department of Psychology, Royal Holloway College, University of London, Egham, Surrey, UK. a.t.smith@rhbnc.ac.uk |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Discrimination (Psychology)
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physiology Humans Motion Perception / physiology* Photic Stimulation / methods Psychometrics Psychophysics |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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