September 2015
Volume 15, Issue 12
Vision Sciences Society Annual Meeting Abstract  |   September 2015
Lower in Contrast, Higher in Numerosity Estimation
Author Affiliations
  • Quan Lei
    Department of Psychology, Northeastern University
  • Adam Reeves
    Department of Psychology, Northeastern University
Journal of Vision September 2015, Vol.15, 776. doi:
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      Quan Lei, Adam Reeves; Lower in Contrast, Higher in Numerosity Estimation. Journal of Vision 2015;15(12):776. doi:

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

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When equal numbers of gray disks and white disks are intermingled on a dark gray field, there appear to be more gray disks than white ones (Lei & Reeves, 2014). It is yet unclear whether this contrast-dependent illusion occurs only in a discrimination task where subjects have to pay attention to both gray and white disks in order to compare their numerosities. In this study subjects were asked to estimate the absolute numerosity of either gray or white disks intermingled on a dark gray field. In Experiment 1, subjects estimated the numerosity of gray disks (Gray trials) and white disks (White trials) in separate blocks. In each block, the irrelevant (not-to-be-reported) disks had a fixed numerosity of 50 and the relevant (to-be-reported) disks varied in numerosity between 20 and 80, in increments of 10. In Experiment 2, using the same stimuli, Gray trials and White trials were randomized, and subjects did not know which set of disks to estimate until they were given a prompt at the end of each trial. In Experiment 3, Gray trials and White trials were also randomized, but before the disks onset, subjects were cued as to which color to estimate on each trial by presenting either a gray or a white fixation cross. In all three experiments, the estimated numerosity was significantly larger for gray disks than that for white disks, at all numerosity levels. In a control experiment where both gray and white disks were presented alone, no difference in estimated numerosity was found. All these results are consistent with the discrimination data of Lei & Reeves (2014), as if the illusion arises from sensory interactions between intermingled stimuli of different contrasts prior to any cognitively-driven comparisons.

Meeting abstract presented at VSS 2015


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