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Disentangling signal from noise in visual contrast discrimination

Nature Neuroscience volume 4, pages 1146–1150 (2001)Cite this article

Abstract

Human ability to detect stimulus changes (ΔC) decreases with increasing reference level (C). Because detection performance reflects the signal-to-noise ratio within the relevant sensory brain module, this behavior can be accounted for in two extreme ways: first, the internal response change ΔR evoked by a constant ΔC decreases with C (that is, the transducer R = f(C) displays a compressive nonlinearity), whereas the internal noise is independent of R; second, ΔR is constant with C but the noise level increases with R. A newly discovered constraint on human decision-making helps solve this century-old problem: in a detection task where multiple changes occur with equal probabilities, observers use a unique response criterion to decide whether a change has occurred. For contrast discrimination, our results supported the first account above: human performance was limited by the contrast transducer nonlinearity and an almost constant noise.

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Figure 1: Signal detection theory1 framework and the trial sequence.
Figure 2: Threshold increments versus contrast functions for four observers (different symbols).
Figure 3: Response criteria expressed in Z-scores of false alarms (ZFA) as a function of the sensitivity index, d′.
Figure 4: Criterion (ZFA) ratio and α-ratio as a function of the normalized pedestal-contrast ratio for all possible pairwise combinations of the four baseline contrasts used in the main experiment.

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Acknowledgements

We thank E. Ahissar, H. Barlow, D. Foster, C. Lorenzi, Z.-L. Lu, M. Morgan, A. Reeves, J. Solomon, J. Thomas and C. Tyler for their comments.

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Authors and Affiliations

  1. Laboratoire de Psychologie Expérimentale, Centre National de la Recherche Scientifique (CNRS) and René Descartes University, 71 Avenue Edouard Vaillant, Boulogne-Billancourt, 92774, France

    Andrei Gorea

  2. Department of Neurobiology/Brain Research, Weizmann Institute of Science, Rehovot, 76100, Israel

    Dov Sagi

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  1. Andrei Gorea
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  2. Dov Sagi
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Correspondence to Andrei Gorea.

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Gorea, A., Sagi, D. Disentangling signal from noise in visual contrast discrimination. Nat Neurosci 4, 1146–1150 (2001). https://doi.org/10.1038/nn741

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