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What Determines the Response: Test or Reference?The stability of sensory memory has been studied by presenting a reference stimulus, a delay, and a test stimulus. As has been pointed out by Lages and Treisman (1998 Vision Research 38 557-572), the usual measure of performance depends only on the effect of test variations on the responses. The Weber fraction characterizing performance is more properly called the test stimulus Weber fraction. We measure the relative contribution of the test and reference to the response by the ratio of the test Weber fraction to the reference Weber fraction. The stimuli were two dark lines on a bright background. Seven reference separations, varying from 9.5 to 16.7 arc min, were intermixed in each run. Interstimulus intervals (ISI) of 50, 200 and 2000 msec and intertrial intervals (ITI) of 500 and 2500 msec were investigated. When the ISI was short (50 or 200 msec), for both ITIs, responses were determined equally by the test and reference. For the long ISI (2000 msec), the reference stimulus contributed less. However, only for the 500 msec ITI (and not for all observers) was the contribution of the reference stimulus negligible, as Treisman's criterion setting theory might suggest.
Document ID
Document Type
Conference Paper
Chukova, S. V. (Pavlov Inst. of Physiology Saint Petersburg Russia)
Ahumada, A. J., Jr. (NASA Ames Research Center Moffett Field, CA United States)
Null, Cynthia
Date Acquired
August 20, 2013
Publication Date
January 1, 1998
Subject Category
Computer Programming and Software
Meeting Information
European Conference on Visual Perception(Oxford)
Funding Number(s)
PROJECT: RTOP 505-65-53
Distribution Limits
Work of the US Gov. Public Use Permitted.