Purpose : Examining Köhler's “displacement-effect” experimentally, we tried to see whether or not our results can support his theory of “self-satiation”. At the same time, we conducted experiments on Gibson's “adaptation”, and tried to compare it with Köhler's “self-satiation”. Experiments :
Apparatus-Apparatus and conditions in the present experiments were the same as those in the previous experiments (see Report I).
Stimuius figures-Fig, 1 indicates the stimulus figure used in Exp. I and Exp. II fig. 5 and 7 those used in Exp. III and Exp. IV respectively.
Procedure-Exp. I, III and IV were done in similar ways. For a considerable length of time, Sub. fixated the fixation point which was on the left side (or right) of I. F. (Inspection Figure), while V. F. (Variable Figure) was covered with a white screen on the other side. When the white screen was removed, Sub. could see V. F., Sub. compared I. F. with V. F. in respect of apparent size (in Exp. I), apparent curvature (in Exp.III), or with the breadth and length (in Exp. IV) of the figures. With various lengths of inspection time, we measured amounts of “displacement” using Wirth's “Complete series method”.
In Exp. II, the procedure of projecting the figure was the same as that used in the previous wark (see Report I).
Results :
1) Under prolonged inspection, an object diminishes its apparent size ; a circle becomes smaller, while the distance between the parallel-lines becomes narrower and the length of them becomes shorter. We must add here that the amount of diminution by “self-satiation”, is generally slight, and the personal difference in the amount of effects is considerably large.
2) The rate of diminution due to “self-satiation”(and also to Gibson's “adaptaion”) is at first comparatively large, then gradually becomes smaller till it draws closely to zero.
Here, we must say that these phenomena depend greatly upon the experimental procedure ; the curve which shows the amounts of the effects in the case of Exp. I differs from the one obtained in Exp II (see Fig. 2 (Exp. I) and Fig., 3 (Exp. II)).
3) From these experiments we can conclude that Gibson's “adaption” is the same phenomenon as Köhler's “self-satiation”.
4) Investigating these phenomena, we are inclined, contrary to Köhler's theory of “displacement”, to think that every part of a figure displaces itself from a weak satiated area to an intensive area. We, also, conclude that the phenomenon of “self-satiation”, as Obonai says, is a phenomenon which results from the process in which the intensively satiated area appears smaller than it's objective size.
5) “Self-satiation” must be distinguished from “after-effect”, for the former is the prerequisite of the latter ; the former exists as a phase of development of the exciting-process, while the latter exists as a phase of the decline of the exciting-process.
In this repect, Köhler's “theory of figural after-effects” seems to have a defect ; it makes no distinction between “self-satiation” and “after-effect”. Therefore, it can not help but fall into explanatory difficulty. However, Köhler would be able to explain his facts without inconsistencies, if he did not regard the phenomena of “self-satiation”-as he did in the explanation of “after-effect”-as the reactions of the figure-current of T. F. on the figure-current of I. F., but regarded it as an action of the figure-current of I. F. itself.
6) The phenomenon of “self-satiation” appears more remarkably on color and depth symptoms than they do on displacement symptoms.
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