Upon a cylinder, slowly revolving by fine clockwork, strips of different colored cardboard are fastened, and observed through a hole in a screen. (See illustration on the preceding page.) The time of each rotation is measured precisely. By observation it is found that the period of rotation seems to vary with the colors on the cylinder. By combining colors differently through a long and tedious series of investigations on many people, it is being determined what part this sort of influence plays in mental processes. “When things look gay, time seems short.” Psychology seeks the laws of such happenings.
LOCALIZATION OF SOUNDS.
They are the most familiar things which in our science become the strangest. Not to know where you are when seasick, still less where your mind is, is common enough. Our next experiment will trace our power to know where sounds are to the same origin as seasickness.
Seasickness starts in the ear. In its cavity are three small tubes, each bent in a circle, and filled with fluid. The three sit at right angles to each other, like the three sides at the corner of a room or a box. Consequently, in whatever direction the head is moved, the fluid in some one of the tubes is given 403 a circular motion. Hanging out into the tubes, from their sides, are hairs or cilia, which connect with nerve cells and fibres that branch off from the auditory nerve. When the head moves the fluid moves, the hairs move, the cells are “fired off,” a nervous current is sent up to the brain, and a feeling of the head’s peculiar motion is consequent.
As for seasickness: this nerve current, on its way to the brain, at one point runs beside the spot or “centre” where the nerve governing the stomach has its origin. When the rocking of the head is abnormally violent and prolonged, the stimulus is so great that the current leaks over into this adjoining “centre,” and so excites the nerve running to the stomach as to cause wretchedness and retching. Deaf mutes, whose ear “canals” are affected, are never seasick.
But normally the amount of ear-feeling which we get by reason of moving our head in a particular direction comes in a curious way to be a measure of the direction of sound. The feelings we get from our skin and muscles in turning the head play a similar rôle. We turn our ear to catch a sound. We do this so frequently for every point, that in time we learn to judge the direction of the sound by the way we would have to turn the head in order to hear the sound best. Thereafter we do not have to turn the head to get the direction, for we now remember the proper feeling and know it. This memory of the old feeling is our idea of the present direction. If we never moved our heads we never could have any such notion of the location of sounds as at present—perhaps none whatever.
MENTAL ORIGIN OF NUMBERS.
Number! surely there can be nothing mysterious here; no “law” to be discovered about one, two, three? Well, the next time you shake hands, ask the man what he feels. A hand. Then ask further and he will feel five fingers. Now ask rightly and he will feel any number of distinct spots of pressure. But the real pressures were practically the same all through. Why, then, did he feel first one, then five, then eight, ten, or a dozen? So with the objects we become acquainted with through any of our senses! Why does the same bit of nature now stand before us “one tree,” and now a myriad of leaves and branches? Why do the same outer groupings fall into such different inner groupings? Why does not the result of each little nerve of the millions continually played on in eye, ear, and skin stand out by itself, and we have so many million feelings?
To explain this: the first time a child opens his eyes he sees, as Professor James says, but “one big, blooming, buzzing confusion.” Not till some “whole” (knife) be broken up into parts (blade, handle) and each part be mentally perceived in immediate succession the one after the other can the idea of “twoness” ever be possible to that child. The “twoness” is a feeling of distinct nature apart from the two terms (blade, handle). It rises from the “shock of succession.” It is one of the “modified states” wrought by one element on another, which we studied in our first experiment. Once lodged in the mind, the feeling may be remembered and reawakened, like any other. Thereafter the two parts or terms may come before the mind, awaken this feeling of twoness, and now stand side by side, simultaneously and numerically separate.
These are the primary laws of number perception. Our experiments illustrate and prove them. Though the nerves lying under a needle point are really several in number, the pressure on them is commonly felt as “one prick.” The area is so small that usually, through life, all the nerves have been pressed together. They have not been split up and pressed enough times in succession among themselves for a memory of “twoness” to have been developed among them. But, by proper manipulation, not unlike some of the processes of hypnotism, yet perfectly normal, the “twoness” of some other group of nerves can be yoked to the feeling resulting from the pressure of a particular needle point. Thereupon the one needle 404 will feel like two, as distinctly and clearly as any real two.