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Long Luu, Alan Stocker; Choice-induced biases in visually perceived numerosity. Journal of Vision 2017;17(10):745. doi: 10.1167/17.10.745.
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© ARVO (1962-2015); The Authors (2016-present)
Making a categorical decision can systematically bias our subsequent perception of a stimulus. We have previously shown that these biases are well predicted by an observer model that maintains self-consistency across a sequential assessment of the same sensory evidence (Luu/Stocker, VSS 2015). However, experimental evidence so far has been limited to low-level visual stimuli such as motion direction (Jazayeri/Movshon 2007, Zamboni et al. 2016) or local visual orientation (Luu/Stocker, VSS 2015). Thus it was unknown whether self-consistent behavior generalizes to tasks involving high-level, more abstract visual stimuli. To answer this question, we conducted a set of psychophysical experiments probing visually perceived numerosity. The main experiments consisted of the following sequential decision-estimation task: In each trial, subjects (N=4) were briefly presented with an array of white dots of various size (diameter: 0.07-0.35 degs) shown on gray background within a circular aperture (7 degs). The number of dots was chosen with equal probability to be anywhere between 33 and 47. After stimulus presentation, subjects first had to report whether the number of dots was larger or smaller than 40. Subsequently, they then also had to provide an actual estimate of the number of dots. In order to modulate stimulus uncertainty, we tested two stimulus conditions that differed in presentation time (either 0.02 s or 1 s). We found the same characteristic biases in subjects' estimates of the number of dots as in the previously reported experiments using low-level visual stimuli. The biases are well accounted for by the self-consistent observer model, outperforming alternative models. Our results suggest that self-consistency may play a fundamental and general role in sequential decision-making tasks.
Meeting abstract presented at VSS 2017
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