@article{oai:nagoya.repo.nii.ac.jp:00008310, author = {後藤, 倬男 and GOTO, Takuo}, journal = {名古屋大学文学部研究論集. 哲学}, month = {Mar}, note = {The purpose of this study is to verify the effects of the combination of stimulus-consitions in Ebbinghaus illusion (Fig.1A).Magnitude of illusion(MI)of the center circle (CC) was measured in the interrelation with the following three stimulus-conditions; (1) the distance (D)between surrounding circles(SCs) and the CC (D=3.1, 8.6, 15.8mm),(2)the diameter ratio (R)(R=1/2, 1/1, and 2/1)of the SCs to the CC, and (3) the number (N)(N=1,2, and 4) of the SCs(Exp.1). Then, the variations of the MI were investigated by repeating the measurement 64times on one subject under the same experimental conditions as in the Exp.1 for (Exp.2). Two personal computers(NEC:PC-9801)were used for presenting the many kinds of standard stimulus(SS) and comparison stimulus(CS), and also controlling efficiently the responses of the subject(Fig.2). Six undergarduate students with normal visual acuity served as the subjects. These subjects were instructed to compare the apparent size between the SS presented randomly at the centerof one display and the CS presented at the another display as a single circle. The spatial distribution of the SS to the CS was changed in the order of left(L)-right (R)-R-L in Exp.1 and 2. The size of the CS was varied through the method of limits. The results are as follows: (1)The CC of the Ebbinghaus illusion was clearly overestimated under the R=1/2 (SCCC). This tendency was consistent when using nine combinations of other two stimulus-conditions (Fig.3). The above trends were enhanced as the number of the SC increased. However, surrounding the CC by the SCs was not necessary in the Ebbinghaus illusion, because the contrastive change of the apparent size of the CC was verified in the case of the N=1 and the N=2, in which the SC didn't surround the CC (Fig.4). As estimated under the comparatively limited range of figure locomotion inside the display, the consistent variation of the MI was not gained as a function of the distance between the SCs and the CC(Fig.5). However, with four SCs (N=4), the magnitude of overestimation of the CC generally decreased as the distance between the SCs and the CC enlarged with the diameter ratio of 1/2 (SCCC). The MI variations caused by the difference of the above distance between the SCs and CC were compared with those of the Delboeuf illusion(Fig.1B) studied by Ogasawara(1952) in regard to the following three kinds of distance between the SC and the CC. Fig.11 represents three distances ①between the circumference of the CC and the inner circumference of the SCs(INNER), ②between the circumference of the CC and the center of the SCs(CENTER), and ③between the circumference of the CC and the outer circumference of the SCs (OUTER). Since the resultant patterns of the MI variations were different from any of those estimated by Ogasawara'S results, it may by concluded that the Ebbinghaus illusion was due to the "contrastive judgement" conducted between the SCs and the CC. (2)In the repeated observations in Exp.2, the tendency of the MI gained from one subject was similar to that of the average MIs obtained from six subjects in Exp.1(Figs.3,5,7, and 8). However, the MIs under the all three kinds of stimulus-condition tend to shift to the "overestimation" in the process of the repeated observations. As shown in Fig.10, the magnitude of overestimation under the R=1/2 increased as a function of the trial of repetition. Contrarily, the magnitude of underestimation under the R=1/1 and the R=2/1 decreased as a function of the number of trial-repetition. Consequently, the MI turned to overestimation in the R=1/1 at the latter part of reptition(Fig.7 and 12). And the underestimation greatly decreased even with the R=2/1(Fig.10). The R=2/1 resulted in the greatest gradient of the MI variation (Table 1). Hence, the total MI of the Ebbinghaus illusion, which was defined as the difference between the MI with the R=1/2 and that with R=2/1, decreased as a function of the number of the repetition. The decrease of the total MI took the same trend as the results of the studies conducted on the effect of repeated observation of the optical illusion (Judd, 1905; Lewis, 1908; Kohler and Fishback, 1950a,b; Dewar, 1967a,b,c,d, 1968; Barclay and Comalli, 1970; Letourneau, 1976). However, the rate of the above-mentioned decrease was the smallest with the N=4 in which the stimulus configuration represents the typical apprearance of Ebbinghaus illusion(Table 2). In conclusiion, the judgement of "overestimation" gained in the repeated observations is different from the judgement of "contrast in size", provided that the observations were conducted with three stimulus-conditions as independently as possible in each stimulus presentation., p.58 1行 誤 中央円よりも大きい場合 正 中央円よりも小さい場合、p.58 2行 誤 円よりも小さい場合には 正 円よりも大きい場合には}, pages = {53--76}, title = {大きさの円対比錯視(Ebbinghaus 錯視)に関する実験的研究(Ⅳ)―付加円と中央円の直径比・付加円数・両円間距離等の刺激条件および観察回数の効果について―}, volume = {33}, year = {1987} }