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Performance asymmetries in visual search demonstrate failure of independent-processing models

Zenger, Barbara and Fahle, Manfred (2000) Performance asymmetries in visual search demonstrate failure of independent-processing models. Vision Research, 40 (19). pp. 2677-96. ISSN 0042-6989. doi:10.1016/S0042-6989(00)00116-4.

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We report psychophysical data from orientation-popout experiments that are inconsistent with a rather general decision model. Stimuli consisted of 121 line segments arranged on an 11×11 grid. There were two tasks: in the 1-Singleton Task all lines except one had the same orientation, and observers had to report which quadrant contained the singleton. In the 3-Singleton Task three quadrants contained orientation singletons and observers had to identify the quadrant without singleton. These tasks can be viewed as asymmetric search tasks, in which either a singleton-quadrant has to be found among three homogeneous quadrants, or a homogeneous quadrant has to be found among three singleton-quadrants. Using tools from signal-detection theory we show that the large performance asymmetries between 1-Singleton and 3-Singleton Tasks are inconsistent with any model that makes two (very basic and common) assumptions: (1) independent processing of the four quadrants and (2) an ideal-observer decision. We conclude that at least one of the two assumptions is inadequate. As a plausible reason for the model failure we suggest a global competition between salient elements that reduces popout strength when more than one singleton is present.

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Additional Information:Received 28 June 1999; received in revised form 12 January 2000. © 2000 Elsevier Science Ltd. We would like to thank Marc Repnow for developing the C library that was used in these experiments, and for his assistance in various computer-related problems; Christoph Zenger for stimulating discussions and an outline of the proof presented in Appendix A; and Steffen Egner and Oliver Landolt for their comments on an earlier version of this manuscript. Financial support was provided by the German Research Council (DFG: Forschergruppe Neuroophthalmologie and SF13 517) and by Caltech’s Division of Biology.
Group:Koch Laboratory (KLAB)
Funding AgencyGrant Number
German Research CouncilDFG: Forschergruppe Neuroophthalmologie
German Research CouncilSF13 517
Subject Keywords:Human psychophysics; Modeling; Visual search; Performance asymmetry; Signal detection theory
Issue or Number:19
Record Number:CaltechAUTHORS:20130816-103240195
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Official Citation:Barbara Zenger, Manfred Fahle, Performance asymmetries in visual search demonstrate failure of independent-processing models, Vision Research, Volume 40, Issue 19, September 2000, Pages 2677-2696, ISSN 0042-6989, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:40552
Deposited By: KLAB Import
Deposited On:05 Feb 2008 23:45
Last Modified:09 Nov 2021 23:49

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