September 2018
Volume 18, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2018
Adjusting visual illusions for differential sensitivity to target size decreases the likelihood of differentiating action from perception.
Author Affiliations
  • Patrick Laflamme
    Psychology, University of British Columbia
  • Robert Whitwell
    Psychology, University of British Columbia
  • James Enns
    Psychology, University of British Columbia
Journal of Vision September 2018, Vol.18, 59. doi:
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      Patrick Laflamme, Robert Whitwell, James Enns; Adjusting visual illusions for differential sensitivity to target size decreases the likelihood of differentiating action from perception.. Journal of Vision 2018;18(10):59.

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      © ARVO (1962-2015); The Authors (2016-present)

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Vision researchers have relied on compelling pictorial illusions to argue both for dissociations between action and perception (multiple visual-systems – MVS - proponents) and against them (common visual system – CVS - proponents). A methodological issue that divides these researchers is whether the effects of illusions on action and perception should be adjusted for baseline differences in sensitivity to size, prior to making the comparisons. Here we use Monte-Carlo simulations to explore how adjusting for the response sensitivity function influences the comparison of illusion effects across response modes. We generated data from multivariate distributions based on typical parameters reported in the literature, before adjusted the effects of the illusion using three techniques: index, zero variance, and a Taylor-approximated application of Fieller's theorem. For each unique combination of parameters, we contrasted pairs of unadjusted and pairs of adjusted illusion effects and computed the observed Type I error (alpha) and II error (beta) values. We used a pseudo d' measure to incorporate both alpha and beta into a single metric of efficiency. The zero variance method yielded a small pseudo d' with unacceptably high alpha. The index method yielded the smallest pseudo d', with a moderate alpha combined with high beta. Among the adjustment methods, Fieller's method yielded the best control over alpha, but at the cost of increased beta. When alpha and beta rates were considered together, unadjusted measurements were, surprisingly, the most efficient. Our findings warrant two recommendations: 1) the Fieller-adjusted effects of the illusion in a given response mode are preferable to other adjustment methods; and 2) the unadjusted effects of the illusion should be used to compare between response modes. These analyses imply that ongoing debates between proponents of MVS and proponents of CVS should be based on unadjusted measures of the same illusion for each response mode.

Meeting abstract presented at VSS 2018


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