Abstract
It has been written among others by Volkmann, Gösser, .Frank, that negative after-images were influenced by the contour figures on the projection surface. But they have not studied systematically enough these phenomena as such.
It is the purpose of this study to investigate these phenomena and, if could, to find out some explannations for them.
At first, I had my subjects project a circular after-image on a homogeneous surface. Then the after-image grew fainter and fainter from edge to centre, and became at last a small circle and disappeared. But once projected on a straight line, the same circular after-image was, so to speak, absorbed into the contour line beginning to change the form at edge. Moreover when a closed contour figure was drawn on the projection surface, there was a phenomenal difference in the behavior of the after-image between inside and outside of the figure.
Generally speaking, the contour figure influenced the after-image in the direction in which the figure phenomenally appeared.
According to W. Köhler, the phenomenal appearance of the contour figure must be the psychological picture of a stationary equilibrium distribution in the corresponding processes of the brain. So, it seems to me that the after-image is influenced by a stationary equilibrium distribution in the processes of the brain.
If this assumption is true, it is expected to occur that when one project the same after-image on the varied contour figures, there will appear phenomenal differences respectively. For the distributions corresponding to the varied contour figutes must be very different.
In order to test this, I had my subjects project a circular after-image in turn on the centre of circle, square, and triangle of equal area. The results in each case, as might have been expected, greatly differed from each other.
In the next place, I wanted to see the effect of the position of projection in the contour figure upon the after-image and had my subjects project a little circular after-image On the varied positions of a square (centre, near a corner, near a side). The results showed that the after-image moved and disappeared in very different ways according to the differences of the positions.
The effect of “Figure” and “Ground” upon the after-image was tested also, and the results served to confirm the above-mentioned assumption.
Now, we face here on a problem; why after-image is influenced by the distribution corresponding to the contour figure? I could ascertain in a preliminary series of experiments the following facts that the forces of distribution corresponding to the after-image were weakened more and more as time passed by. While, on the contrary, the forces of distribution corresponding to the contour figure do not get weakened as time passes by, and have always fairly constant strong distribution. Such being the case, when these two forces are brought about simultaneouslY at the pSychophysical field, they affect each other, and it is natural that the weaker force (after-image) should be influenced by the stronger one (contour figure).
