111. What is the ultimate end of every nervous process?
112. What are typical movements of self-preservation?
113. What are typical movements of play?
114. Is play more than a general exercise of the body?
115. Are all inherited movements possible immediately after birth?
116. What is the difference between reflexes and instincts?
§ 13. THOUGHT AND MOVEMENT
Consciousness is not a factor in reflex or instinctive movements. But these movements soon enter into a twofold connection with consciousness. (1) When such movements occur, they often result in consciousness. They are either seen, or perceived through the sense of touch or through the kinesthetic sense. These images of the movement become associated with the images originating from the sensory stimulations which give rise to the movement. (2) In consequence of this association the visual, touch, and kinesthetic images of the movement, particularly the most common, the kinesthetic, may themselves produce this movement to which they owe their existence. The mere thought of how one feels when performing a movement brings about, if it is vivid enough, the movement itself. The hearing of dance music awakens the kinesthetic ideas of dancing, and these become real movements, although perhaps only swaying movements of the body or the head. Vivid thinking similarly brings about whispering of words. Even vivid imagination of the movement of a foreign body has such powers. A passionate and excited billiard player thinks of the hoped-for movement of the running ball. This leads to imagery of a similar movement of his own body, and the result is the actual movement, rather ridiculous to the onlooker because it is entirely purposeless.
Through this connection with consciousness instinctive movements become voluntary movements. The term _voluntary_ means just this connection with consciousness; it has no other meaning.
Suppose a child sees something white and glittering and puts it instinctively into his mouth. It happens to be a lump of sugar. Its taste is pleasant. It is retained, dissolved, and swallowed. All the impressions, occurring at about the same time, become associated: the sight of the thing, the movements of the arm and hand, the taste, the movements of the tongue and the lips. The more frequently this thing happens, the more firmly established are the associations. Later the sight of sugar reproduces at once its taste, the visual and kinesthetic images of the movements, and the movements themselves--the arm is stretched out, the tongue and lips making sucking movements--although the sugar may be lying so far away that it cannot be touched. The child’s consciousness then contains what we have previously called will, and what may also be called desire: a vivid impression accompanied by pleasantness, sensations of restlessness, and an image of a pleasant conclusion of the whole experience. We say then that the child wills, desires, to have the sugar.
We can will to do only that which in its elements we have previously done by instinct. If we do not know how a movement feels when we perform it, of course we cannot bring it about by way of our consciousness, that is, by our will. Children have as much command of speech as they have acquired by instinctively producing speech sounds in response to accidental stimulations. This instinctive production occurs usually rather late in the case of certain sounds, as _k_, _r_, _sh_; and accordingly, in spite of all special efforts on the part of the parents, children learn to produce those sounds only at that late time. We presuppose, of course, that they are not deaf. For in deaf children the speech sounds instinctively produced do not enter into an association with the kinesthetic sensations and therefore cannot be voluntarily reproduced; that is, the children remain dumb. Many a grown person remembers that all his attempts at learning the pronunciation of a certain sound in foreign speech (take for example the gutteral German _r_, or the German _ch_, or the French nasal sounds) were in vain until by a mere accident, instinctively, he pronounced that very sound. After that he had command of it.
This interweaving of the instinctive reactions of the body with conscious life is of the greatest practical significance. However well adapted the inherited reflexes may be to the purpose of keeping the young animal alive, they are very insufficient in meeting the ever growing complications of life. And they are not perfect even in the beginning. A reflex is the response to a present and direct impression upon the organism; but very similar impressions may come from things of different properties. Poisonous substances often look and taste like articles of food. The enemy assumes the attitude of a friend welcoming you. Reflex action is powerless to give the organism the protection needed in such cases. Instinct is easily deceived. But as soon as the harmful consequences impress themselves upon the organism, the instinct is modified, and in the future these consequences will be avoided. The instincts are ready-made institutions intended to be applied to average conditions. Their readiness and completeness is in so far of inestimable advantage to the organism. If it had to learn everything necessary for life, it could not survive. But for the manifold deviations of the external world from the average no provision can be made in this manner.
The variation of the organism’s response is made possible by the existence of higher nerve centers, that is, of connecting neurons of a higher order, more remote from the sensory and motor points of the body. Let us imagine the proverbial reaction of a child to the sight of a flame, and discuss the successive stages of development by the help of figure 15. (1) The visual stimulation starts a nervous process from _s_{1}_, which passes through the bulb and spinal cord into the muscles of the arm at _m_{1}_. A small part of the current may branch off at _a_ and, instead of passing down towards _b_, take the direction of _v_. But the resistance in this direction is for the present so high that only an insignificant part of the process can take this way, and so no corresponding motor response is noticeable.
[Illustration: FIG. 15.--“A BURNT CHILD FEARS THE FIRE.”]
(2) While all this is still going on and the child’s arm is still moving forward, the heat of the flame acts as a pain stimulus at _s_{2}_. The nervous process produced passes over _c_ and _d_ to the muscles at _m_{2}_, whose contraction results in the arm’s being pulled back. This results in a third stimulation at _s_{3}_, which we need not trace farther here. But not the whole of the nervous process passes from _c_ down to _d_. A part of it, of considerable absolute magnitude because of the intensity of stimulation, passes from _c_ up to _p_ and thence over _k_ down to _d_ and finally also into _m_{2}_. This process going from _p_ to _k_, according to a general law of nervous activity, tends to attract other, weaker nervous processes, if the neuron connections make this possible. Consequently the nervous process from _s_{1}_ to _a_ is now turned mostly into the path _a-v-p_ and only an insignificant part of it continues to go from _a_ towards _b_. The consequence is that the resistance of the path _a-v-p-k-d_ is soon reduced to less than the resistance of the path _a-b_. The great significance of this fact becomes clear in the third stage of development.
(3) At some later time the flame again acts as a visual stimulus. But now, because of the change of resistance just explained, the nervous process takes for the most part the path over _a-v-p-k-d_, and the reaction follows at _m_{2}_ instead of at _m_{1}_. The child has learned to avoid the flame. The child, when seeing the flame, is conscious of the pain, as imagery, without having to receive the actual stimulation at _s_{2}_.
Thus the inflexible regularity of reaction gives place to another type of reaction, an adaptation, not only to those conditions which at the time make their impression upon the organism, but also to those conditions which are mere future possibilities. The experience of the past guides the organism into the future.
