Zero-dimensional noise:the best mask you never saw


The transmission of weak signals through the visual system is limited by internal noise. Its level can be estimated by adding external noise, which increases the variance within the detecting mechanism, causing masking. But experiments with white noise fail to meet three predictions: (a) noise has too small an influence on the slope of the psychometric function, (b) masking occurs even when the noise sample is identical in each two-alternative forced-choice (2AFC) interval, and (c) double-pass consistency is too low. We show that much of the energy of 2D white noise masks extends well beyond the pass-band of plausible detecting mechanisms and that this suppresses signal activity. These problems are avoided by restricting the external noise energy to the target mechanisms by introducing a pedestal with a mean contrast of 0% and independent contrast jitter in each 2AFC interval (termed zero-dimensional [0D] noise). We compared the jitter condition to masking from 2D white noise in double-pass masking and (novel) contrast matching experiments. Zero-dimensional noise produced the strongest masking, greatest double-pass consistency, and no suppression of perceived contrast, consistent with a noisy ideal observer. Deviations from this behavior for 2D white noise were explained by cross-channel suppression with no need to appeal to induced internal noise or uncertainty. We conclude that (a) results from previous experiments using white pixel noise should be re-evaluated and (b) 0D noise provides a cleaner method for investigating internal variability than pixel noise. Ironically then, the best external noise stimulus does not look noisy.

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Divisions: College of Health & Life Sciences > School of Optometry > Optometry
College of Health & Life Sciences > Clinical and Systems Neuroscience
College of Health & Life Sciences
College of Health & Life Sciences > School of Optometry > Centre for Vision and Hearing Research
Additional Information: Creative Commons Attribution Non-Commercial No Derivatives License
Uncontrolled Keywords: noise masking,contrast detection,gain control,suppression,human vision,Ophthalmology,Sensory Systems
Publication ISSN: 1534-7362
Last Modified: 04 Jan 2024 08:09
Date Deposited: 27 Nov 2012 09:54
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
http://www.jour ... (Publisher URL)
PURE Output Type: Article
Published Date: 2012-09-29
Authors: Baker, Daniel
Meese, Timothy (ORCID Profile 0000-0003-3744-4679)

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