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Lana OKUBO, Kazuhiko YOKOSAWA, Masataka SAWAYAMA, Takahiro KAWABE; Why does a disk subjectively disappear in Ninio’s extinction illusion?. Journal of Vision 2020;20(11):723. doi: https://doi.org/10.1167/jov.20.11.723.
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© ARVO (1962-2015); The Authors (2016-present)
People generally believe that they can coherently comprehend the entire visual field. Counterintuitively, however, several psychophysical phenomena show that visual objects in the peripheral visual field go unnoticed. For example, in Ninio’s extinction illusion, a dark disk at the intersection of gray grids against a white background often goes unnoticed even though the contrast level of the disk is supra-threshold. Why do observers fail to be aware of the disk in this illusion? By combining a psychophysical experiment with a computational analysis, we tested a hypothesis that the visual system does not distinguish the signal of the disk at the intersections of the gray grid from the signal of just the intersections, and interpret that the disk does not exist at the intersections. In the psychophysical experiment, a disk was presented at or near one of four grid intersections in half of the trials. Results indicated that the sensitivity (d') for detecting the disk at the intersection (but not near the intersection) decreased with the disk eccentricity. In the computational analysis, the energy relationship between the visual signal of the disk at the intersection and the signal of the intersection was evaluated. The two-dimensional difference of Gaussians with various sigma sizes was convolved with the stimuli, and the energy ratio of the disk signal to the sum of the disk signal and the intersection signal were calculated. Results indicated that the energy ratio decreased with the stimulus eccentricity when spatial frequency analysis in the periphery was considered. Moreover, the d’ for detecting the disk as a function of eccentricity was well described by the exponential function of the energy ratio. These results indicate that the indistinguishability of the disk signal from the intersection signal causes the disk to subjectively disappear in the extinction illusion.
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