事象関連電位によるリップスの大きさ錯視の検討

概要

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We examined the event-related potentials (ERPs) under the condition that four participants compared a single circle (comparison stimulus; visual angle: 1.0°) to center circle surrounded by two additive circles (Lipps size illusion figure; standard stimulus) and responded to apparent size of the single circle as large or small by a key pressing. The constant method was used, and the surrounding circles were prepared for six kinds of diameter, constructing 1/4 (0.25°/1.0°), 1/2 (0.5°/1.0°), 2/2 (1.0°/1.0°), 3/2(1.5°/1.0°), 4/2 (2.0°/1.0°), and 6/2 (3.0°/1.0°) surrounding/center circle-ratios. The ERPs were obtained at four scalp sites of Fz, Cz, Pz, and Oz. The center circle was overestimated for ratio of 1/4 and 1/2, and underestimated for 3/2, 4/2, and 6/2, showing a conversion from overestimation to underestimation under the contrast process. Although several components of the ERPs were emerged under the observation of Lipps size illusion, no components were proportionally changed in response to the psychometric function produced by the subjective large-or-small judgment. It is suggested that the amplitude of some ERP components may covary with the assimilation, but not with the contrast process.
2011-03-15