Perceptual distortions of speed at low luminance: Evidence inconsistent with a Bayesian account of speed encoding

Stephen T. Hammett, Rebecca A. Champion, Peter G. Thompson, Antony B. Morland

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Our perception of speed has been shown to be distorted under a number of viewing conditions. Recently the well-known reduction of perceived speed at low contrast has led to Bayesian models of speed perception that account for these distortions with a slow speed 'prior'. To test the predictive, rather than the descriptive, power of the Bayesian approach we have investigated perceived speed at low luminance. Our results indicate that, for the mesopic and photopic range (0.13-30 cd m-2) the perceived speed of lower luminance patterns is virtually unaffected at low speeds (4 deg s-1). We show here that the results can be accounted for by an extension to a simple ratio model of speed encoding [Hammett, S. T., Champion, R. A., Morland, A. & Thompson, P. G. (2005). A ratio model of perceived speed in the human visual system. Proceedings of Royal Society B, 262, 2351-2356.] that takes account of known changes in neural responses as a function of luminance, contrast and temporal frequency. The results are not consistent with current Bayesian approaches to modelling speed encoding that postulate a slow speed prior. © 2006 Elsevier Ltd. All rights reserved.
    Original languageEnglish
    Pages (from-to)564-568
    Number of pages4
    JournalVision Research
    Volume47
    Issue number4
    DOIs
    Publication statusPublished - Feb 2007

    Keywords

    • Computational models
    • Human vision
    • Speed encoding

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