Poor encoding of position by contrast-defined motion
Second-order (contrast-defined) motion stimuli lead to poor performance on a number of tasks, including discriminating form from motion and visual search. To investigate this deficiency, we tested the ability of human observers to monitor multiple regions for motion, to code the relative positions o...
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| Format: | Article |
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Elsevier
2004
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| Online Access: | https://eprints.nottingham.ac.uk/32314/ |
| _version_ | 1848794382093778944 |
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| author | Allen, Harriet A. Ledgeway, Tim Hess, Robert F. |
| author_facet | Allen, Harriet A. Ledgeway, Tim Hess, Robert F. |
| author_sort | Allen, Harriet A. |
| building | Nottingham Research Data Repository |
| collection | Online Access |
| description | Second-order (contrast-defined) motion stimuli lead to poor performance on a number of tasks, including discriminating form from motion and visual search. To investigate this deficiency, we tested the ability of human observers to monitor multiple regions for motion, to code the relative positions of shapes defined by motion, and to simultaneously encode motion direction and location. Performance with shapes from contrast-defined motion was compared with that obtained from luminance-defined (first-order) stimuli. When the position of coherent motion was uncertain, direction-discrimination thresholds were elevated similarly for both luminance-defined and contrast-defined motion, compared to when the stimulus location was known. The motion of both luminance- and contrast-defined structure can be monitored in multiple visual field locations. Only under conditions that greatly advantaged contrast-defined motion, were observers able to discriminate the positional offset of shapes defined by either type of motion. When shapes from contrast-defined and luminance-defined motion were presented under comparable conditions, the positional accuracy of contrast-defined motion was found to be poorer than its luminance-defined counterpart. These results may explain some, but possibly not all, of the deficits found previously with second-order motion. |
| first_indexed | 2025-11-14T19:15:18Z |
| format | Article |
| id | nottingham-32314 |
| institution | University of Nottingham Malaysia Campus |
| institution_category | Local University |
| last_indexed | 2025-11-14T19:15:18Z |
| publishDate | 2004 |
| publisher | Elsevier |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | nottingham-323142020-05-04T20:31:18Z https://eprints.nottingham.ac.uk/32314/ Poor encoding of position by contrast-defined motion Allen, Harriet A. Ledgeway, Tim Hess, Robert F. Second-order (contrast-defined) motion stimuli lead to poor performance on a number of tasks, including discriminating form from motion and visual search. To investigate this deficiency, we tested the ability of human observers to monitor multiple regions for motion, to code the relative positions of shapes defined by motion, and to simultaneously encode motion direction and location. Performance with shapes from contrast-defined motion was compared with that obtained from luminance-defined (first-order) stimuli. When the position of coherent motion was uncertain, direction-discrimination thresholds were elevated similarly for both luminance-defined and contrast-defined motion, compared to when the stimulus location was known. The motion of both luminance- and contrast-defined structure can be monitored in multiple visual field locations. Only under conditions that greatly advantaged contrast-defined motion, were observers able to discriminate the positional offset of shapes defined by either type of motion. When shapes from contrast-defined and luminance-defined motion were presented under comparable conditions, the positional accuracy of contrast-defined motion was found to be poorer than its luminance-defined counterpart. These results may explain some, but possibly not all, of the deficits found previously with second-order motion. Elsevier 2004 Article PeerReviewed Allen, Harriet A., Ledgeway, Tim and Hess, Robert F. (2004) Poor encoding of position by contrast-defined motion. Vision Research, 44 (17). pp. 1985-1999. ISSN 1878-5646 Second-Order Motion First-Order Motion Position Direction http://www.sciencedirect.com/science/article/pii/S004269890400166X doi:10.1016/j.visres.2004.03.025 doi:10.1016/j.visres.2004.03.025 |
| spellingShingle | Second-Order Motion First-Order Motion Position Direction Allen, Harriet A. Ledgeway, Tim Hess, Robert F. Poor encoding of position by contrast-defined motion |
| title | Poor encoding of position by contrast-defined motion |
| title_full | Poor encoding of position by contrast-defined motion |
| title_fullStr | Poor encoding of position by contrast-defined motion |
| title_full_unstemmed | Poor encoding of position by contrast-defined motion |
| title_short | Poor encoding of position by contrast-defined motion |
| title_sort | poor encoding of position by contrast-defined motion |
| topic | Second-Order Motion First-Order Motion Position Direction |
| url | https://eprints.nottingham.ac.uk/32314/ https://eprints.nottingham.ac.uk/32314/ https://eprints.nottingham.ac.uk/32314/ |