Regional sensitivity for shape discrimination

Regional sensitivity for shape discrimination Spatial Vision , Vol. 13, No. 4, pp. 377– 391 (2000) Ó VSP 2000. Regional sensitivity for shape discrimination REBECCA L. ACHTMAN ¤ , ROBERT F. HESS and YI-ZHONG WANG † McGill Vision Research, Room H4-14, 687 Pine Ave. W., Montreal, Quebec, H3A 1A1, Canada Received 22 October 1999; revision accepted 1 May 2000 Abstract —In a task where subjects had to detect smooth deviations from circularity, we assessed whether performance varied with eccentricity. Our stimuli were circular 4th derivatives of Gaussian contours (CD4s) whose radii were sinusoidally modulated. We used D4s of different peak spatial frequencies and overall diameters. Although performance declined with eccentricity for all radial frequencies tested, once scaling was taken into account, sensitivity was similar at all eccentricities. This was the basis of the scale-invariancealso exhibited by this task. Thus, shape discrimination does not appear to be a specialized function limited to central vision. Keywords : Circularity; local; global; Ž ltering; orientation. 1. INTRODUCTION A number of recent studies have argued that the detection of radial perturbations in circular targets represents a global shape task (Wilkinson et al ., 1998; Hess et al ., 1999). There is psychophysical evidence that such a discrimination is http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Spatial Vision (continued as Seeing & Perceiving from 2010) Brill

Regional sensitivity for shape discrimination

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Publisher
Brill
Copyright
© 2000 Koninklijke Brill NV, Leiden, The Netherlands
ISSN
0169-1015
eISSN
1568-5683
D.O.I.
10.1163/156856800741261
Publisher site
See Article on Publisher Site

Abstract

Spatial Vision , Vol. 13, No. 4, pp. 377– 391 (2000) Ó VSP 2000. Regional sensitivity for shape discrimination REBECCA L. ACHTMAN ¤ , ROBERT F. HESS and YI-ZHONG WANG † McGill Vision Research, Room H4-14, 687 Pine Ave. W., Montreal, Quebec, H3A 1A1, Canada Received 22 October 1999; revision accepted 1 May 2000 Abstract —In a task where subjects had to detect smooth deviations from circularity, we assessed whether performance varied with eccentricity. Our stimuli were circular 4th derivatives of Gaussian contours (CD4s) whose radii were sinusoidally modulated. We used D4s of different peak spatial frequencies and overall diameters. Although performance declined with eccentricity for all radial frequencies tested, once scaling was taken into account, sensitivity was similar at all eccentricities. This was the basis of the scale-invariancealso exhibited by this task. Thus, shape discrimination does not appear to be a specialized function limited to central vision. Keywords : Circularity; local; global; Ž ltering; orientation. 1. INTRODUCTION A number of recent studies have argued that the detection of radial perturbations in circular targets represents a global shape task (Wilkinson et al ., 1998; Hess et al ., 1999). There is psychophysical evidence that such a discrimination is

Journal

Spatial Vision (continued as Seeing & Perceiving from 2010)Brill

Published: Jan 1, 2000

Keywords: CIRCULARITY; FILTERING; LOCAL; ORIENTATION; GLOBAL

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