[PROBLEM] It is reported from the men who saw pesonally Céanne at his work that he used to keep looking at the object for a long while, -from several minutes to fifteen or twenty minutes at times, and would give touches every now and then. (1, 3). On the other hand, expressing his own attitude of prolonged inspection (we call it hereafter PI), Rodin also said, “Facing to my creation, I look at the model for a long time and think” (14). Céanne moreover remarked, “Time and reflection change the sight little by little, till we come to understand” (13) ; while Rodin remarked, “Things are seen analytically when looked at first, but in time they come to appear as a totality” (14) ; The prolonged inspection of the figure will fill me with inspired imagination, and at last I can idealize the figure. (3, 15)
[METHOD] Geometrical, figures, each of which was drawn on a sheet of gray paper (the thickness of each line being 1/2mm) eith a lead pencil (H. B.) were used as stimuli. The subject was asked to keep inspecting the drawing with native attitude at the distance of reading on the desk until he was ordered to stop PI. Whenever he experienced any change in the appearance of the drawing, he had to draw the new sight on a sheet of paper placed on the right side of the stimulus. From 5 to 10 minutes were necessary to complete an experiment including the time of the subject's drawing activity.
[RESULTS]
A. Destruction of ‘Typical’ or ‘Normal’
Gestalt When a Necker's cube was inspected continually, Kopferman's so-called “gut, sicher und eindeutig” character as a cube (9) was lost, till the principle of so-called “good continuity” of lines was broken. Fig. (3)-A, which was shown by Kopfermann as an example having the sight “of a hexagon with diagonal lines” and “of two dimensions, ”transformed into a cube and brought forth many other spontanceous changes in Gestalt during P.I.
Kopfermann point out that Fig. (4)-A was seen as “a quadrilateral with a diagonal line” and was difficult to be seen as the sum of triangles through the division by a diagonal line (9). The results of our PI showed many spontaneous Gestalt changes through destruction of organization.
About Fig. (5)-A, Wertheimer (17) and Kopfermann (9) pointed out that it was seen as a piled figure of two quadrilatirals and was an example of the “good Gestalt”. ThroughPI, however, we exprienced the formation of rather “bad Gestalt”.
B. On Grouping As for the influence of PI upon grouping, it was found that the grouping, through the factors of closure, similarity and proximity, occurred only in limited times. Again, several similar straight lines drawn parallel to one another at equal distances showed changes continually in their mutual groupings during PI.
C. Imaginative Appearance In contrast with the results of PI of printed words by Severance and Washburn (13) in our nonsence geometrical patterns, they were given manings through PI and colored with the character of something imaginative.
D. Hidden Figure When we were set naively in PI of Fig. (10)-A, the capital letterrs of W. Koehler, K. Koffka and M. Wertheimer stood out spontaneously as figures. Originally, such letters did not appear spontaneously as figures (5, 17), but, here, the fact became valid only in some limited time. As for the problem of the ‘figure’character of some hidden forms by Gottschalt, the hidden form appeared as a ‘figure’ quite literally according as the inspection time prolonged, even if we inspected naively (Fig. 11).
E. Problem of Figure-Creation Koehler gave an example in which, ‘favoring’ or ‘picking out’some part of the pattern made that part appear as a ‘figure’ in the case of Fig. (12, 5).

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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).

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In most of the previous studies of the Gibson effect, a straight line is used as a T- figure to test the after-effect of a curved line which has been inspected as the I-figure for a considerable length of time. Under this condition, the straight line looks curved eith an opposite curvature and this phenomenon is considered to be due to a kind of distortion induced by the I-figure in its surrounding field. It seems to me, however, that the apparent distortion of the T-figure namely of a straight line, is not necessarily an exact representation of the change occuring in the field. Displacement of all points along a straight line may be due not only to the previous inspection of the curve line but also to the cohesive character of a line as an integrated whole. Therefore, in this experiment, in place of a line I employd a dot as the T-figure and tried to make a thorough inquiry into the nature of the after-effect.
A curved line (convex to the left, measured 4cm in its chord with 1cm of displacement at the center) was fixated for 90 seconds at its middle point from 90cm distance. Immediately after the inspection, a dot was presented with a fixation mark. The positions of the dots employed were given in Fig. 1 ; for instance, at times it was objectively 4mm right of the point where the middle point of the curved line had been (11) and at times it was 1cm right and 2cm above (3) and so forth. The perceived position of a dot was localized, either in the vertical or in the horizontal direction, by having O adjust two indicators until a dot and the indicators arranged themselves in a row. Pops of the indicators were not affected by the after effect as they were far enough from the position where as the I-figure had been presented. All of the three O's were students of psychology who had no knowledge of the aim of the experi-ment. Localization of a dot, not preceded by the inspection of the I-figure, served as a standard and the difference between it and the local zed point after inspection defined the displacement induced by the after effect. Results of the three O's were graphically shown in Fig. 3, 4 and 5. Vectoors are averages of five meaurements.
First, I would like to take into consideration the direction of the displacement. According to the satiation theory developed by W, Köheler, all dots should be displaced towards the center of the curvature of the I-figure, since the displacement should occur in the direction receding from the place whrere the satiation springs from. On the conditions of this experiment, therefore, the dots in the upper half of the field should move downwards and towards the right and those in the lower half of the field should move upwards and towards the right. As you will see in Fig. 3, 4 and 5, however, the results of the three O's clearly show that the dots were displaced in general upwards and towards the right regardless of their positions in the stimulus figure. Hence, the results seem not to be in accord with the satiation theory.
Secondly, I would like to compare the amounts of the displacements of the dots. If three dots placed vertically in a row are considered together, it will be seen that the displacement of the middle one was always the largest, though al of them were displaced more or less towards the right. These findings are in good agreement with the results of the previous experiments by different investigatiors who emloye a straight line as the T-figure, that the after effect resulted in the phenomental distortion of the straight line with the curvature oppsite from that of the I-figure. And it is interesting to note that what Gibson called the adaptation, the apparent decrease in the curvature of the I-figure during the inspection period, was reported by all O's, and besides, the amount of adaptation was somewhat larger on the upper half of the curved line than on the lower half.

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Figural after-effects depend upon two temoral factors, namely the duration of inspection period (i) and the time interval between inspection and test periods (t). This study was planned to measure figural after-effects (A) as a function of two variables, i and t, whereas, up to the time, many experimenters (1, 3, 6, 12) had studied the after-effects as a function of one variable, either i or t.
Experimental conditions and procedure : Black outline circles on white paper were used as the inspection- and test- objects. (See Fig. I) The right test-circle was the standard stimulus and the left circle was the variable stimulus. Six test-sheets with various sizes of the left circle were prepared. But, after each inspection period only one test-sheet was used. The inspection- and test-sheets were presented at the distance of 3 meters from the subject, who observed them binocularly. The inspection- and test-sheets with their surroundings of white paper, were illuminated homogeneously at the brightness of 2 millilamberts. The durations of the inspection periods were 1, 2, 5, 15, 60 and 240 seconds. The simplified “method of comleete series” was used. As the measure of figural after-effects, the amount of apparent shrinkage of the test-circle in diameter was adopted.
Results and discussion : The upper curve in Fig. 2 shows the time course of development of the figural after-effects that are tested immediately after the inspection periods. It indicates that a 1 second inspection is long enough to produce a considerable amount of the figural after-effects and the prolongation of the inspection period can hardly bring about the increase in them. The lower curve shows the time course of development of the figural after-effects that are tested 5 seconds after the inspection period. It froms an ordinary growth curve. Since these two curves are obtained from the same series of experiments, the difference between the two should be attributed to the difference in t, that is the sole difference between their conditions. It is very interesting that Gibson & Rander and Hammer, who used the method of adjustment, which would require at least 5 seconds for one setting, reported the results which resemble our lower curve rather than our upper curve.
The curves in Fig. 3 show the time courses of disappearance of figural after-effects after the inspection periods of various durations. All of these curves start from almost the same level and decreasing with negative acceleration reach zero. Their qualitative characteristics are similar to one another and to those of Hammer's curve. Inspection of Fig. 3 reveals that, in general, the long r the inspection period is, the slower is the rate of the decrease in the after-effects.
The schematic representation of our results requires a three-dimensional graph like Fig. 4. And, according to the mathematical formulation of Mueller, who used Hammer's data, the disappearance course of figural after-effects was represented by the exponential function, A=A_oe-kt. Our results would suggest that in this formula the parameter k should be taken as a function of i and A_o a constant which is independent of i.

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Purpose The purpose of the present study is to determine figural after-effects (Köhler-effect) and Gibson's negative after-effects quantitatively as a function of the inspection time and of the time after inspection.
Method The appratus is shown in Fig 1. Figures used in Exp. I, Exp. II and Exp. IV are shown in Fig. 2, Fig. 7 and Fig. 10 respectively. The general procedure was the same as Köhler's and Wirt's “Vollreihen Mothode” was used to measure the amount of after-effect. The course of the declination of after-effects. The course of the declination of after-effects was caught every five seconds by subjects' judgement. The length of the inspection period were 1, 5, 15, 30, 60, 120 and 240 sec.
The test for the declining process of figural after-effects in Exp. III under the same arrangement of figures as Exp. I was performed by Hammers' second method which eliminated the factor of successive induction. Exp. V was the test-experiment performed under the condition shown in Eig. 13 which was considered to be the test situation of Exp. IV.
Results 1) Under the same conditions of experiments, the Köhler-effect and the Gibson-effect were demonstrated to be identical process.
2) The amount of after-effects (including Gibson's negativre after-effects) depends upon the size and arrangement of figures. If the size and arrangement of figures are kept constant, the amount of after-effects percieved immediately after the inspection of I. F. remains constant irrespective of the length of the inspection period.
On the contrary as regards colour-effects, the longer the inspection time is, the more conspicuous are the effects.
3) The amount of after-effects is maximum immediately after inspection, at first it diminishes quickly, then later gradually. When the inspection time is shorter, the gradient of the decay-curve is sharper. The decay-curves of after-effects strictly agree with Muller's formula.
4) The so-called growth-curves of the after-effects that have been determined by Hammer etc. are shown to be nothing more than thecurve of after-effects considered as a function of the inspection time under the condition of several seconds after the inspection of I. F. Therefore, these curves reveal only the limited case of the growing process of after-effects.
5) The gradient of the decay-curve of after-effects that in the decay-curve under the condition of the larger I. F. (see Fig. 2) is slower than that of the smaller I. F. (see Fig. 7). The longer the inspection time is, the more prominent is the defference of the gradient in decay-curves.
6) Although in determining the decay-process of after-effects the method of successive judgement is a very convenient procedure as Hammer has pointed out, there is a significant difference between the results by the method of successive judgement (Hammer's first method) and those by the method of white-paper-insertion (Hammer's second method) in our experiments. In order to get the correct data, it is neccessry to modify the data obtained by the method of successive judgement.
7) Gibson-effects are influensed more or less by the direction of the curved-line. This fact may be explained by the factor of “Zentrishe Schrumpfung des Sehraumes” (Obonai's theory) and by the factor of the potential-illusion in comparative judgement of parallel curved-line (V. F. and T. F.)
8) In experiment on figural after-effects, especially in studying temporal factors, we must take into consideration the judgement mechanism of the subjects.

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In my first report I stated that placing a small point at various places near a figure and studying the direction and the quantity of the displacement of the point by measuring the expansion and contraction of the phenomenal distance between the point and an auxiliary point, I found many interesting facts.
This method being indirect, I worked out some new ways of studying the displacement of the point more directly, and as a result of experimenting, I came to the counclusion that the same tendency sould be seen in the new method as well.
Following this I made a further study in detail of the displacement of the small point inside and outside a figure by means of the first method, which is comparatively easier to operate and greater in efficiency.
As a result, it has been found out that the direction of the displacement of the point lies in direct intersection with the equal potential line obtained by the formula based on the theory reported in Yokose's former report, and also that the greater the gradient of the potential, the greater the displacement. In other words, the curved line in Fig. 14 is the equal potential line obtained by Yokose's formula, and the arrows show the displacement direction of the point at those positions by the experimental results.
This relation is similar to the phenomenon of the equal electric potential and the electric force line around electric charge in physics. Hence, as in Kohler's theory of percept, I would like to postulate the psycho-physical field force-and hence the vector-field-of the cerebrum which corresponds to the figure. At the time, the results of the experiment show that a way for quantitative analysis of the vector-field in the study of shape has been opened.

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