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Saki Takao, Katsumi Watanabe; The Ebbinghaus illusion changes numerosity perception. Journal of Vision 2018;18(10):1172. doi: 10.1167/18.10.1172.
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© ARVO (1962-2015); The Authors (2016-present)
A circle surrounded by smaller (larger) circles appears larger (smaller) (Ebbinghaus illusion: Tichener, 1901; Ebbinghaus, 1902). Whether other perceptual qualities are modulated inside the space surrounded by the circles (inducers) has not been fully examined. In the present study, we investigated whether the Ebbinghaus illusion would modulate numerosity perception. In the experiment, participants fixated on the fixation-cross that was continuously presented at the center of the display. In each trial, some dots were presented inside the fixed circle areas at the left and right side of the fixation cross for 200 ms. For each side, the number of dots were selected randomly from 2, 4, 6, 8, 10, or 12. Two inducers surrounded the two areas where the dots were presented. Each inducer was consisted of 4 circles, which were either smaller, the same size as, or larger than the dot area, and presented 200 ms before, during, and 200 ms after the dot presentation (i.e., for 600 ms). Twelve participants were asked to report which dot area contained the larger number of dots. In the experimental trial, one small inducer and one large inducer were presented with their positions randomized. In the control trial, two inducers with the same size as the dot area were presented. Participants performed 720 experimental trials and 360 control trials in a randomized order. The results showed that the number of dots tended to be perceived larger with the small inducer than the large inducer. Evidently, the present study demonstrated that not only size perception but also numerosity perception were modulated by the size of the inducers in the Ebbinghaus illusion.
Meeting abstract presented at VSS 2018
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