図形残効の実験的研究 (III)

Abstract

According to Köhler and Wallach's satiation theory, “test-objects displaced from the satiated area” is the fundamental principle of figural after-effects. So, the displacement of the test-dot from the inspection-dot would be the most simplified situation of figural after-effects. The author studied the spatial factors determining the displacement in such situation.In the first place, the apparent growth and shrinkage of the distance between two test-dots (s) were measured as a function of the distance between two inspection-dots (h) (Fig. 1). The results showed that the maximal growth occurred when h/s=1/2, and the maximal shrinkage was obtained when h/s=2, and that the optimal condition of displacement did not depend primarily upon the distance between the inspectionand the test-dots (Figs. 2, 4, 5). These results are just the same as those of the inspectionand test-circles as investigated in the previous paper (this journal, 1954, 25, 195-206), the only difference from the previous results being that the amount of after-effect increased only slightly and not proportionally, as s increased.In the second place, the apparent rise and fall of a test-dot were measured as a function of the distance between the inspectionand the test-dots (Fig. 6). These results (Fig. 7) were compared with the results of many experiments of the author and other researchers, but we could not find any consistency in the optimal distances between inspection- and test-objects (Table 1).These facts suggest that a mosaic model of displacement mechanism is not suitable to explain figural after-effects even in the most simplified situation.Next, the author studied the after-effect of two inspection-dots upon the two test-dots which were not on same line with inspection-dots (Fig. 8). It was found that after-effect (shrinkage) decreased as the line of inspection-dots became distant from the line of test-dots, but it did not disappear up to a considerable distance (Fig. 9).The effect of the size and the shape of inspection-objects was also investigated.After-effect increased slightly when inspection-dots were enlarged, but it did not when inspection-dots were replaced by horizontal bars and their length was extended (Fig. 10).