As skill is acquired by practice in the performance of complex activities, the undue muscular tension of the initial stage is gradually relaxed.
There is another way in which the radiation of nerve impulse may be caused, entirely distinct from the lack of use or skill. Muscular stiffness may be induced in the case of activities so thoroughly habitual as to be normally performed automatically. The cause of muscular stiffness now to be considered is the attempt to perform complex activities mechanically, that is, by consciously directing the individual component movements and muscular contractions involved in the actions. Involuntary contractions of associated and antagonist muscles take place under these conditions, in addition to the voluntary exercise of the muscles normally exerted in the movements.
This fact may be illustrated by attempting to write a few lines, and forming every stroke of each letter by a distinct exercise of the will. If you keep up this attempt for ten minutes you will find that you press upon the paper with many times your accustomed weight. The hand stiffens in consequence of the close attention paid to its movements. This stiffness will extend to the arm, and even to the shoulder, if the exercise be continued long enough and with sufficient intensity of attention to the hand.
Another good illustration of this form of muscular stiffening may be found by walking upstairs, and paying the same kind of attention to the muscular actions. Try to ascend a single flight of stairs, performing each elementary movement by a distinct volitional impulse. Pause on the first step to secure perfect balance on one foot; raise the other foot, bending the leg at the knee, then place this foot carefully on the next higher step. Now gradually shift the weight of the body from the lower to the higher foot; as the body inclines forward, exert the muscles of the back and sides to preserve your balance; then contract the leg muscles so as to raise the body to the higher step, with the weight supported on that foot. Repeat this operation for each step. To mount one flight of stairs in this way will tire you more than ascending a half dozen flights in the ordinary automatic way.
All four of the types of involuntary muscular contraction just described may be combined in a single instance. An inexperienced violin soloist, such as a student playing at a conservatory recital, often exemplifies this. Nervousness and awkwardness cause him to tremble; the scratchy sound of his tones makes him twitch and start; meanwhile, the close attention paid to his fingering and bowing stiffens his arms and completes his difficulty.
The vocal organs are peculiarly subject to the forms of involuntary muscular contraction under consideration. Each of the causes of muscular tension may exert its special influence on the voice. Let us go over the ground once more, this time with special reference to the actions of the throat muscles.
(a) Reflex Actions of the Muscles of the Vocal Organs, Independent of Direct Sensory Excitation
Involuntary actions of the vocal organs normally occur in response to stimuli furnished by the emotions and feelings. Every one is familiar with the shout of triumph, the sigh of relief, and the ejaculation of surprise. Some emotions cause a convulsive stiffening of the muscles of the vocal organs so complete as to render tone-production for a time absolutely impossible. "Speechless with terror," "breathless with apprehension," are expressions which accurately describe psychological processes. A crowd of people watching a difficult rescue of a drowning man is silent so long as the uncertainty lasts. A shout instantly goes up when the rescue is seen to be safely effected. Both the silence of the nervous strain and the shout of relief are normal involuntary responses to the emotional states.
(b) The Influence of Nervousness on the Vocal Action
Nervous conditions exert a striking influence on the operations of the voice. Even when our self-control under trying conditions is complete in all other respects we are often unable to prevent our voices betraying our nervous state. Stage fright, an extreme form of nervousness, sometimes deprives the sufferer entirely of the power of speech. This temporary loss of vocal command is not due to an inability to innervate the muscles of the vocal organs; on the contrary, it is caused by extreme muscular stiffness due to the violent, though involuntary, contraction of all the muscles of the vocal organs.