September 2017
Volume 17, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2017
Overestimation of the number of elements in a three-dimensional stimulus is dependent on the size of the area containing the elements
Author Affiliations
  • Yusuke Matsuda
    Faculty of Marine Technology, Tokyo University of Marine Science and Technology
  • Koichi Shimono
    Faculty of Marine Technology, Tokyo University of Marine Science and Technology
  • Saori Aida
    School of Computer Science, Tokyo University of Technology
Journal of Vision August 2017, Vol.17, 151. doi:10.1167/17.10.151
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      Yusuke Matsuda, Koichi Shimono, Saori Aida; Overestimation of the number of elements in a three-dimensional stimulus is dependent on the size of the area containing the elements. Journal of Vision 2017;17(10):151. doi: 10.1167/17.10.151.

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

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Abstract

Numerosity perception has been intensively examined using two-dimensional (2-D) stimuli, but has almost never been investigated using three-dimensional (3-D) stimuli. Recently, however, it was reported that a stereoscopic 3-D stimulus is perceived to have more elements than a stereoscopic 2-D stimulus when both contain the same number of elements. This suggests that the depth structure of the stimulus plays a role in numerosity perception. We examined the effect of the size of the area containing the elements on the overestimation phenomenon, using random-dot stereograms for 3-D and 2-D stimuli, which consisted of black square elements (6.7 * 6.7 arcmin) scattered in a circular area (4.4, 8.9, or 13.3 arcdeg in diameter). When the stereograms were fused, the 3-D and 2-D stimuli were perceived to have two transparent surfaces and a single surface, respectively. Observers performed a numerosity discrimination task, where they identified which of the two stimuli (presented side-by-side) had a greater number of elements. The number of elements was maintained constant at 50, 100, or 150 for the 3-D stimulus and varied for the 2-D stimulus to calculate the Weber fraction as an index of the degree of numerosity overestimation for the 3-D stimulus. The results indicated that the Weber fraction increases with the size of the circular area and the number of elements. The results can be explained in terms of a process or processes, with an output representing the perceived numerosity. The process(es) loads the visual system more heavily when the observer estimates the number of elements scattered in a 3-D space than when a single surface is estimated. This results in the overestimation of the elements in the 3-D stimuli.

Meeting abstract presented at VSS 2017

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