周辺視野の方位識別課題におけるoblique effect, visual crowding の検討

抄録

Oblique effect is a phenomenon that is cardinal (horizontal and vertical) orientations are easily distinguishable from slightly tilted ones, while oblique orientations are not. In the periphery of the visual field, a phenomenon of visual crowding that is visual targets become indistinguishable when surrounded by flankers occurs. The oblique effect has been widely reported in the center of the visual field, but no notable results have been obtained in the periphery of the visual field. Although both phenomena affect perception, there has been little previous research linking the two, and no reported cases have confirmed the oblique effect during crowding. In the current study, we designed experiments that combined both phenomena using human 10 subjects in their 20s with normal vision. In experiment 1, oblique effect was confirmed in the center of the visual field. In experiment 2, oblique effect was tested in the periphery of the visual field at an eccentricity of 8° from the center of the visual field. In experiment 3, oblique effect was tested in the circumstance that evokes visual crowding at an eccentricity of 8° from the center of the visual field. Analyses based on the signal detection theory and Mann-Whitney U test showed discrimination of oblique orientations from slightly tilted ones were harder than discrimination of cardinal orientations in the periphery of the visual field than the center (center cardinal n＝20, oblique n＝20, U＝25.5, p＜0.001, periphery cardinal n＝60, oblique n＝60, U＝328, p＜0.001), and also showed the depression of the discrimination performance, but existence of the oblique effect in the circumstance of the visual crowding (cardinal n＝60, oblique n＝60, U＝586.5, p＜0.001) .