圖形の持續視とその殘効 I

Gibson効果に關する實驗的研究

抄録

In the study of the visual pricess of perception, it is important that not only the factor of stimulus distribution be taken into consideration. From this viewpoint, the experiment of the figural after-effect proposed by Köhler and Wallach is very interesting but it would seem that it should be retested on the ground of quantification from the neutral stand-point because they imply a bold physiological hypothesis on the basis of qualitative observation. Recently many writers have examined the quantity of after-effect, but many of these studies comprise only partial research of the fact and consequently they can not test the validity of the Köhler hypothesis as a whole. Moreover it is difficult to theoreize about the facts within the results of their investigations systematically because the figures and methods they used were different one from another.
Taking these points into consideration, it is the perpose of the present writer to measure the quantity of the figural after-effect and to ascertain the functional principles working there in order to test the contradictory theories that have been fequently suggested.
The present writer suggests that this phenome-non can be differentiated into two part, the “displacement effect” and the “size effect”.
1. Experimental study of the Gibson effect.
The phenomenon named “Gibson effect” is the earliest discovery and is the most frequently measured phenomenon concerning the “displacement effect” Now the writer proposes a modification of Gibson's method in order to measure the after-effects of a curved line.
(1) Gibson suggested a hypothesis about adaptation and after-effects of the prolonged inspection of the curved line. However, his method of measuring adaptation was the same in principle as that of measuring after-effects, and accordingly his adaptation theory may be said to have no factual basis at all.
(2) The writer confirmed that the previously exposed curved line affected the subsequently exposed straight line causing it to curve in the opposite direction and that, this effect was produced only by the influence of prolonged inspection of the curved line and not by the measuring operation including the direction of adjustment and the constellation of those figures (Exp. A. B.)
(3) with respect to the results of our exp. B in which the curved line (I. F.) gradually changed to assume the farm of a straight line through prologed inspection, Gibson might suggest that this was caused by adaptation process, but the existence of this process could not be confirmed by this sort of experiment only.
Köhler and Wallach, etc. explain this phenomenon on the basis of the distance between the inspection line (I. F.) and the test line (T. F.).
They do not assume the process of normalization.
(4) The present writer confirmed that the curvature changed in the direction of a straight line even in the case when the I. F. coincided with the T. F. (Exp. C. D.). To explain the results of exp. A, B, C, and D. systematically, it would be more convenient to do so interms of normalization hypothesis than in terms of Köhler's theory.
(5) When, under the condition of Exp. C. in which the I. F. exactly coincided with the T. F., the curvature of the lines was changed variously, the direction of the displacement of the test line was always the same.
(6) Whether the I. F. more curved or less curved than the after-effect of the curved line always produced the decrement of curvature od T. F. (Exp. F, G, H.).
These results were in disagreement with Köhker's explanation of Gibson effect based upon the principles of displacement and distance paradox.
(7) To test Köhler's hypothesis directly, the author compared the effect of the curved I. F. upon the curved T. F. (Exp. 11) with that of the linear I. F. upon the curved T. F. (Exp. 12).