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Conference Paper: The detection of smooth curves in jagged contours

TitleThe detection of smooth curves in jagged contours
Authors
Issue Date2002
PublisherPion Ltd.. The Journal's web site is located at http://www.perceptionweb.com
Citation
The 25th European Conference on Visual Perception, Glasgow, Scotland, 25-29 August 2002. In Perception, ECVP Abstract, 2002, v. 31 n. Suppl., p. 153-154 How to Cite?
AbstractJagged contours with sharp edges, such as those formed by the fractal edge of the Mandelbrot set, have a lower correlation in position and shape between different scales than smooth curves. The more jagged the contour, the lower the correlation. In principle, coarse changes in position of a curve, be it jagged or smooth, can be coded by using operators tuned to low-luminance spatial frequencies; but, to code the fine changes in position of a jagged contour, small operators are required. Since a sharp-luminance- transition contour is visible to both high-spatial-frequency-tuned and low-spatial-frequency-tuned operators, the question arises whether coarse changes in shape are coded via low-spatial-frequency- tuned cells, or via high-spatial-frequency-tuned cells whose outputs are pooled by a coarse-scale higher-order mechanism. We investigated this issue by conducting two experiments. In the first experiment, we show that shape-amplitude detection thresholds of a sinusoidal contour increase with the blur of the contour, and that the threshold functions are parallel over a large range of shape spatial frequencies, implying that high-(luminance)-spatial-frequency-tuned mechanisms that are more shape-and-position sensitive come into play whenever they can be supported. In the second experiment, we measured the threshold for shape-amplitude detection of a low-shape-frequency sinusoidal contour in the presence of shape harmonics of various amplitudes, for both (luminance) spatial-frequency unfiltered, and high-pass spatial-frequency filtered, contours.We found no differ- ence in thresholds for shape-amplitude detection when using filtered and unfiltered stimuli. We conclude that coarse shape information is coded with the smallest operators available. In the context of a model of vision that emphasises the role of self-similar `filters' tuned in spatial frequency, our results are consistent with the idea that contour shape is encoded via high-spatial- frequency-tuned cells, possibly of the highest spatial frequency capable of responding to the contour. [Supported by URC (Hong Kong) and NSERC (Canada).]
DescriptionOral presentations: Perceptual organisation
Persistent Identifierhttp://hdl.handle.net/10722/197959
ISSN
2015 Impact Factor: 0.917
2015 SCImago Journal Rankings: 0.518

 

DC FieldValueLanguage
dc.contributor.authorHayes, A-
dc.contributor.authorKingdom, FAA-
dc.contributor.authorPrins, N-
dc.date.accessioned2014-06-17T02:31:40Z-
dc.date.available2014-06-17T02:31:40Z-
dc.date.issued2002-
dc.identifier.citationThe 25th European Conference on Visual Perception, Glasgow, Scotland, 25-29 August 2002. In Perception, ECVP Abstract, 2002, v. 31 n. Suppl., p. 153-154-
dc.identifier.issn0301-0066-
dc.identifier.urihttp://hdl.handle.net/10722/197959-
dc.descriptionOral presentations: Perceptual organisation-
dc.description.abstractJagged contours with sharp edges, such as those formed by the fractal edge of the Mandelbrot set, have a lower correlation in position and shape between different scales than smooth curves. The more jagged the contour, the lower the correlation. In principle, coarse changes in position of a curve, be it jagged or smooth, can be coded by using operators tuned to low-luminance spatial frequencies; but, to code the fine changes in position of a jagged contour, small operators are required. Since a sharp-luminance- transition contour is visible to both high-spatial-frequency-tuned and low-spatial-frequency-tuned operators, the question arises whether coarse changes in shape are coded via low-spatial-frequency- tuned cells, or via high-spatial-frequency-tuned cells whose outputs are pooled by a coarse-scale higher-order mechanism. We investigated this issue by conducting two experiments. In the first experiment, we show that shape-amplitude detection thresholds of a sinusoidal contour increase with the blur of the contour, and that the threshold functions are parallel over a large range of shape spatial frequencies, implying that high-(luminance)-spatial-frequency-tuned mechanisms that are more shape-and-position sensitive come into play whenever they can be supported. In the second experiment, we measured the threshold for shape-amplitude detection of a low-shape-frequency sinusoidal contour in the presence of shape harmonics of various amplitudes, for both (luminance) spatial-frequency unfiltered, and high-pass spatial-frequency filtered, contours.We found no differ- ence in thresholds for shape-amplitude detection when using filtered and unfiltered stimuli. We conclude that coarse shape information is coded with the smallest operators available. In the context of a model of vision that emphasises the role of self-similar `filters' tuned in spatial frequency, our results are consistent with the idea that contour shape is encoded via high-spatial- frequency-tuned cells, possibly of the highest spatial frequency capable of responding to the contour. [Supported by URC (Hong Kong) and NSERC (Canada).]-
dc.languageeng-
dc.publisherPion Ltd.. The Journal's web site is located at http://www.perceptionweb.com-
dc.relation.ispartofPerception-
dc.titleThe detection of smooth curves in jagged contoursen_US
dc.typeConference_Paperen_US
dc.identifier.emailHayes, A: ahayes@hkucc.hku.hk-
dc.identifier.doi10.1068/v020430-
dc.identifier.hkuros108628-
dc.identifier.hkuros82930-
dc.identifier.volume31-
dc.identifier.issueSuppl.-
dc.identifier.spage153-
dc.identifier.epage154-
dc.publisher.placeUnited Kingdom-

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