図形残効・遡及効果・同時錯視

Abstract

As known quite well, the figural aftereffect occurs in such a way that the apparent extent of the test figure is affected when an inspection figure precedes the test figure, while a so-called assimilation-contrast illusion of the visual extent takes place when they are presented simultaneously. In the present investigation, the effect of the inspection figure upon the estimation of the test figure, besides both of the above mentioned effects, was confirmed, when the test figure precedes the inspection figure. We call this effect“retroactive figural-effect”. The black contour circles on a white card were presented in succession by a revised Dodge-tachisto-scope and Harvard time-apparatus. The spatial arrangement of figures in shown in Fig. 1 where an inspection figure (I) and a test figure (T) of 30mm. in diameter are found on the left side of a fixation point and a comparison figure (C) which is variable in size with 1mm. steps is on the right side. T and C were always presented simultaneously. The PSE was determined by the method of complete series, and it was checked against the constant error in PSE due to possible inhomogeneity between the right and left visual fields. The final results were as follows :1. The retroactive-effect of I. upon the estimation of the extent of T. was conspicuous when I. followed T. The retroactive-effect varied with the extent of I. in a similar manner to that of the figural after-effect, although the amount of the effect was less than that of the latter. T. was underestimated when I. was equal to or larger than T. while it was overestimated when I. was smaller than T. (See Fig. 2)2. The amount of the retroactive-effect. varied not only with the exposure duration of I. but also with the time interval between T. and I. (See. Fig. 3 and 4).3. When T. and I. were presented simultaneously, the typical assimilation illusion of concentric circles was obtained, viz., T. was overestimated or underestimated according to whether it was smaller or larger than I. (See Fig. 5).4. The transition from the simultaneous effect to the figural after-effect or the retroactive-effect occurred at such a temporal interval where the impression of succession of T. and I. appeared on the part of subjects. (See Fig. 5 and Table 7).5. Even if I. was exposured 900 msec. later after the disappearance of T., the retroactive-effect was observed when the observers only with held their verbal reports with respect to the extent of T. until the disappearance of I.. However, if the verbal reports were made immediately after the exposure of T. and C., this effect became weak (See Table 4). These facts seem to suggest that the retroaction became effective through some complex processes involving not only perceptual process but also the memory trace.The results of the present investigation indicate that the adequate theory of the figural after-effect must take into consideration fhe retroaction and the simultaneous induction.