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Detection symmetry and asymmetry

Detection symmetry and asymmetry Detection symmetry and asymmetry J. M. H. du BUF Signal Processing Laboratory, Swiss Federal Institute of Technology, EPFL-Ecublens, CH-1015 Lausanne, Switzerland Received 11 May 1990; revised 28 September 1990; accepted 1 October 1990 Abstract-Experiments were performed on the detection symmetry and asymmetry of incremental and decremental disks, as a function of both disk diameter and duration. It was found that, for a background luminance of 300cd.m-2, thresholds of dynamic (briefly presented) foveal disks are symmetrical for all diameters, and that thresholds of quasi-statically presented disks are symmetrical for large diameters only. Threshold curves of quasi-static incremental and decremental disks are mutually shifted along the log area axis. In order to obtain a better insight into the underlying detection mechanism, additional experiments were performed with halfwave-rectified concentric cosine gratings, i.e. with either incremental or decremental phases. Threshold curves of these gratings proved to be identical, that is independent of polarity, and of the same shape as those obtained with fullwave cosine gratings, though 0.3 log unit shifted in amplitude. The discrepancy between threshold curves of quasi-static disks (asymmetry) and halfwave-rectified gratings (symmetry) is discussed in terms of a multiple-channel theory. INTRODUCTION A considerable amount of research has been done http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Spatial Vision (continued as Seeing & Perceiving from 2010) Brill

Detection symmetry and asymmetry

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Publisher
Brill
Copyright
© 1991 Koninklijke Brill NV, Leiden, The Netherlands
ISSN
0169-1015
eISSN
1568-5683
DOI
10.1163/156856891X00083
Publisher site
See Article on Publisher Site

Abstract

Detection symmetry and asymmetry J. M. H. du BUF Signal Processing Laboratory, Swiss Federal Institute of Technology, EPFL-Ecublens, CH-1015 Lausanne, Switzerland Received 11 May 1990; revised 28 September 1990; accepted 1 October 1990 Abstract-Experiments were performed on the detection symmetry and asymmetry of incremental and decremental disks, as a function of both disk diameter and duration. It was found that, for a background luminance of 300cd.m-2, thresholds of dynamic (briefly presented) foveal disks are symmetrical for all diameters, and that thresholds of quasi-statically presented disks are symmetrical for large diameters only. Threshold curves of quasi-static incremental and decremental disks are mutually shifted along the log area axis. In order to obtain a better insight into the underlying detection mechanism, additional experiments were performed with halfwave-rectified concentric cosine gratings, i.e. with either incremental or decremental phases. Threshold curves of these gratings proved to be identical, that is independent of polarity, and of the same shape as those obtained with fullwave cosine gratings, though 0.3 log unit shifted in amplitude. The discrepancy between threshold curves of quasi-static disks (asymmetry) and halfwave-rectified gratings (symmetry) is discussed in terms of a multiple-channel theory. INTRODUCTION A considerable amount of research has been done

Journal

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

Published: Jan 1, 1991

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