Size matters, but not for everyone:Individual differences for contrast discrimination


It is very well known that contrast detection thresholds improve with the size of a grating-type stimulus, but it is thought that the benefit of size is abolished for contrast discriminations well above threshold (e.g., Legge, G. E., & Foley, J. M. (1980)]. Here we challenge the generality of this view. We performed contrast detection and contrast discrimination for circular patches of sine wave grating as a function of stimulus size. We confirm that sensitivity improves with approximately the fourth-root of stimulus area at detection threshold (a log-log slope of -0.25) but find individual differences (IDs) for the suprathreshold discrimination task. For several observers, performance was largely unaffected by area, but for others performance first improved (by as much as a log-log slope of -0.5) and then reached a plateau. We replicated these different results several times on the same observers. All of these results were described in the context of a recent gain control model of area summation [Meese, T. S. (2004)], extended to accommodate the multiple stimulus sizes used here. In this model, (i) excitation increased with the fourth-root of stimulus area for all observers, and (ii) IDs in the discrimination data were described by IDs in the relation between suppression and area. This means that empirical summation in the contrast discrimination task can be attributed to growth in suppression with stimulus size that does not keep pace with the growth in excitation. © 2005 ARVO.

Publication DOI:
Divisions: College of Health & Life Sciences > School of Optometry > Optometry
College of Health & Life Sciences > Clinical and Systems Neuroscience
Additional Information: Creative Commons Attribution Non-Commercial No Derivatives License
Uncontrolled Keywords: human vision,inhibition,lateral interactions,masking,suppression,surround,Ophthalmology
Publication ISSN: 1534-7362
Last Modified: 28 Feb 2024 08:09
Date Deposited: 25 May 2010 13:09
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
http://www.jour ... ent/5/11/2.full (Publisher URL)
PURE Output Type: Article
Published Date: 2005
Authors: Meese, Timothy S. (ORCID Profile 0000-0003-3744-4679)
Hess, Robert F.
Williams, Cristyn B.

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