Early in life, controls appear to be almost lacking in most sets of neurons, with the result that aimless motions are quite evident. A package of stimuli (sound or light waves, etc.) causing a physical and chemical change in the neurons of a sense organ passes as impulses across the synapses without much hindrance at first, and produces a package of muscular or glandular responses in proportion to its strength. A loud noise brings about a total “jump” all over the baby’s body — almost all the muscles contract. By degrees, the aimless motions decline in number by inhibition at the synapses, and the purposeful motions are facilitated. In time, a specific group of stimuli may call forth a specific muscular reaction.
Gradually we learn not only to inhibit aimless muscular motions of the limbs and body and facilitate purposeful ones, but we parallel this development with inhibitions and facilitations of the tongue, too. As we do so, we make mental connections for tongue control within the upper brain (cerebrum) that are similar to the connections for other muscular reflexes found within the body-coordinating center of the lower, rear portion of the brain (cerebellum).
Some authorities have the theory that as we “think of something” we at times go through the motions of saying the words we are thinking, but we hold back so that the voice is not projected nor is the tongue set in sufficient motion to produce the words. The importance of a large vocabulary now should make sense to you. These many words (symbols) you are required to learn are the raw material for thinking. By arranging and rearranging words, new concepts can be born. In some unknown way, we attach “meaning” to batches of impulses, and convert them into internal sense data.
A great deal is being learned about the areas of the brain by experimenting upon rats, dogs, pigeons, and monkeys. The general activities of the brains of lower animals are similar to ours. In fact, it is no exaggeration to say that what we do when we think is not much more than a lower animal does when it thinks, except that humans have the benefit of acquiring a tremendously greater number of “symbols” with which to think.
Symbols are various things (diagrams, shapes, words, sounds) which stand for the real things. Having learned the connection between a symbol and the real thing, we are able to recall the symbol, and place it in various relationships with other recalled symbols in our minds. By this means, an unlimited number of new combinations can be invented. Symbols are extremely important in human societies. One expert, Dr. A. E. Emerson, of the University of Chicago, offers the opinion that symbols bear the same relation to human societies that genes bear to somatic inheritance!