Of course, the possibility that fanciful images may appear during movement is familiar. If I sit quietly in the forest and at some distance see a stone or a piece of wood or a little heap of dried leaves, etc., it may be that, because of some illusion, I take it to be a rolled up hedgehog, and it may happen that I am so convinced of the nature of the object while I am looking at it that I see how the hedgehog stretches itself, sticks out its paws and makes other movements. I remember one winter when, because of some delay, a commission on which I was serving had failed to reach a village not far from the capital. We had gone to investigate a murder case and had found the body frozen stiff. The oven in the room was heated and the grave-digger placed the stiff body near the oven in order to thaw it out. We at this time were examining the place. After a while I was instructed by the examining justice to see about the condition of the corpse, and much to my disgust, I found it sitting near the oven, bent over. It had thawed out and collapsed. During the subsequent obduction I saw most clearly how the corpse made all kinds of movements, and even after the section, during the dictation of the protocol, my imagination still seemed to see the corpse moving a hand or a foot.
The imagination may also cause changes in color. Once, I saw on my desk, which stood next to a window, a great round drop of water on the left side of which the panes of the window were reflected. (Fig. 11). The whole business was about a meter
from my eye. I saw it repeatedly while working and it finally occurred to me to inquire how such a great drop of water could get there. I had sat at my desk for hours without moving. I must have observed it if it had dropped there. Refraining intentionally from going closer, I started, without avail, to consider how it could have
come. Some time after I examined the drop of water FIG. 11. and found it to be an ink-blot, long ago completely dried, and bearing on its left side a few grains of white cigar ash. I had taken these to be the image of the window, and hence, had immediately attached to it the idea of the shining, raised drop of water. I had altogether overlooked the deep black color of the drop. On the witness stand I would have sworn that I had seen a drop of water, even if I had known the evidence on the matter to be important.
In many cases it is possible to control the imagination, but only when it is known that the images can not be as they are seen. Everybody is aware how a half-covered object at a distance, or objects accidentally grouped in one way or another, are taken for God knows what. Thus once, looking from my desk to my smoking table, I saw an enormous pair of tailor's scissors half-covered by a letter. It remained identical under a number of repeated glances. Only when I thought vigorously that such a thing could not possibly be in my room did it disappear. A few scales of ashes, the lower round of the match safe, the metal trimmings of two cigar boxes half- covered by a letter and reflected by the uncertain light breaking through the branches of a tree, were all that the tailor's scissors was composed of. If there had been such a thing in the house, or if I had believed something like it to exist in the house, I should have sought no further and should have taken my oath that I had seen the thing. It is significant that from the moment I understood the phenomenon I could not restore the image of the scissors. How often may similar things be of importance in criminal trials!
The so-called captivation of our visual capacity plays a not unimportant part in distinguishing correct from illusory seeing. In order to see correctly we must look straight and fully at the object. Looking askance gives only an approximate image, and permits the imagination free play. Anybody lost in a brown study who pictures some point in the room across the way with his eyes can easily mistake a fly, which he sees confusedly askance, for a great big bird. Again, the type of a book seems definitely smaller if the eyes are fixed on the point of a lead pencil with a certain distance
before or above the book. And yet again, if you stand so that at an angle of about 90 degrees from the fixation point, you look at a white door in a dark wall, observing its extent in indirect vision, you will find it much higher than in direct vision.
These examples indicate how indirect vision may be corrected by later correct vision, but such correction occurs rarely. We see something indirectly; we find it uninteresting, and do not look at it directly. When it becomes of importance later on, perhaps enters into a criminal case, we think that we have seen the thing as it is, and often swear that ``a fly is a big bird.''
There are a number of accidents which tend to complete illusion. Suppose that the vision of a fly, which has been seen indirectly and taken for a big bird happens to be synchronous with the shriek of some bird of prey. I combine the two and am convinced that I have seen that bird of prey. This may increase, so much so that we may have series of sense-illusions. I cite the example of the decorative theatrical artist, who can make the most beautiful images with a few, but very characteristic blots. He does it by emphazising what seems to us characteristic, e. g., of a rose arbor, in such a way that at the distance and under the conditions of illumination of the theatre we imagine we really see a pretty rose arbor. If the scene painter could give definite rules he would help us lawyers a great deal. But he has none, he proceeds according to experience, and is unable to correct whatever mistakes he has committed. If the rose arbor fails to make the right impression, he does not try to improve it--he makes a new one. This may lead to the conclusion that not all people require the same characteristics in order to identify a thing as such, so that if we could set the rose arbor on the stage by itself, only a part of the public would recognize it as properly drawn, the other part would probably not recognize it at all. But if, of an evening, there is a large number of decorations on the stage, the collective public will find the arbor to be very pretty. That will be because the human senses, under certain circumstances, are susceptible to sympathetic induction. In the case of the rose arbor we may assume that the artist has typically represented the necessary characteristics of the arbor for one part of the audience, for another part those of a castle, for another part those of a forest, and for a fourth those of a background. But once an individual finds a single object to be correct, his senses are already sympathetically inductive, i. e., captivated for the correctness of the whole collection, so that the correctness passes from one object to the total
number. Now, this psychic process is most clear in those optical illusions which recently have been much on public exhibition (the Battle of Gravelotte, the Journey of the Austrian Crown Prince in Egypt, etc.). The chief trick of these representations is the presenting of real objects, like stones, wheels, etc., in the foreground in such a way that they fuse unnoticeably with the painted picture. The sense of the spectator rests on the plastic objects, is convinced of their materiality and transfers the idea of this plasticity to the merely pictured. Thus the whole image appears as tri-dimensional.
The decorations of great parks at the beginning of the last century indicate that illumination and excited imagination are not alone in causing such illusions. Weber tells ecstatically of an alley in Schwetzing at the end of which there was a highly illuminated concave wall, painted with a landscape of mountains and water-falls. Everybody took the deception for a reality because the eye was captivated and properly inducted. The artist's procedure must have been psychologically correct and must have counted upon the weakness of our observation and intellection. Exner points to the simple circumstance that we do not want to see that things under certain conditions must terminate. If we draw a straight line and cover an end with a piece of paper, every one wonders that the line is not longer when the paper is removed.