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JD Knotts, Alan L.F. Lee, Hakwan Lau; Subjective confidence judgments for motion direction discrimination are centrally biased despite matched objective performance in the periphery. Journal of Vision 2019;19(10):294b. doi: https://doi.org/10.1167/19.10.294b.
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While dissociations between objective and subjective perception are well known in the case of blindsight (Weiskrantz, 1999), finding such a dissociation in normal observers has proven difficult (Kolb & Braun, 1995; Morgan, Mason, & Solomon, 1997; Peters & Lau, 2014; Knotts et al., 2018). Here, we report a dissociation between objective performance (measured by d’) and perceptual confidence judgments on a central-peripheral 2-AFC motion direction discrimination task. Subjects were simultaneously presented with central and peripheral dot motion stimuli and were asked to indicate both the direction of coherent motion in each stimulus and the stimulus (central or peripheral) in which they were more confident in their motion discrimination decision. We found that subjects were strongly biased towards indicating higher confidence in centrally presented stimuli, even when peripheral and central discrimination d’ were matched. This effect was quantified by fitting individual type 2 psychometric curves to individual subject data in which the tendency to bet on the central stimulus was plotted as a function of the difference in d’ between central and peripheral stimuli. Subjects consistently indicated higher confidence in the central stimulus at the psychometric point of objective equality. The paradigm used here may therefore represent a powerful psychophysical tool for isolating subjective visual awareness from objective perceptual signal strength, thereby providing cleaner subjective measures for the study of visual consciousness.
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