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Saori Aida, Tsutomu Kusano, Koichi Shimono; Overestimation of the numbers of elements in a three-dimensional stimulus compared with a two-dimensional stimulus. Journal of Vision 2013;13(9):1229. doi: https://doi.org/10.1167/13.9.1229.
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© ARVO (1962-2015); The Authors (2016-present)
Although many researchers have investigated numerosity judgments, they have tended to focus on numerosity judgments of two-dimensional (2D) stimuli. However, recently, Aida et al (2012) and Schütz (2012) suggested that the numerosity judgment of a three-dimensional (3D) stimulus has an essentially different nature from that of a 2D stimulus. We investigated whether the number of elements of a 3D stimulus (when fused, two transparent surfaces are observed in the same visual direction) would be judged as larger than those of a 2D stimulus (when fused, a single surface is observed) even when both stimuli consisted of the same number of elements. Participants’ numerosity judgments in a stereoscopic space were examined in three experiments, where 2D and 3D stimuli (random-dot stereograms) were presented side-by-side on a monitor and viewed from a distance of 60 cm. In the experiments, participants completed a numerosity discrimination task, where they judged which of the two stimuli had a larger number of elements. Results showed that (1) the 3D stimulus was thought to contain more elements than the 2D stimulus, even when both had the same number of elements, (2) the amount of overestimation increased as a function of the number of elements and relative disparity between the two surfaces of the 3D stimulus, and (3) the ratio of the number of elements in the front surface to that in the back surface of the 3D stimulus had no effect on the amount of overestimation. These results indicate that overestimation in numerosity judgments occurs in stereo domains, suggesting that the visual system takes into account those elements that are possibly hidden by the front surface.
Meeting abstract presented at VSS 2013
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