THE EXPRESSION OF THE EMOTIONS IN MAN AND OTHER ANIMALS

The subject is treated under three Principles: the Principle of Associated Habit; the Principle of Antithesis; and the Principle of the direct action of the nervous system independent of Will and Habit.

THE PRINCIPLE OF ASSOCIATED HABIT.

It is notorious how powerful is the force of habit. The most complex and difficult movements can in time be performed without the least effort or consciousness. It is not positively known how it comes that habit is so efficient in facilitating complex movements; but physiologists admit that “the conducting power of the nervous fibers increases with the frequency of their excitement.” This applies to the nerves of motion and sensation, as well as to those connected with the act of thinking. That some physical change is produced in the nerve-cells or nerves which are habitually used can hardly be doubted, for otherwise it is impossible to understand how the tendency to certain acquired movements is inherited.

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It is known to every one how difficult or even impossible it is, without repeated trials, to move the limbs in certain opposed directions which have never been practiced. Analogous cases occur with sensations, as in the common experiment of rolling a marble beneath the tips of two crossed fingers, when it feels exactly like two marbles. Every one protects himself when falling to the ground by extending his arms, and as Professor Alison has remarked, few can resist acting thus when voluntarily falling on a soft bed. A man when going out-of-doors puts on his gloves quite unconsciously; and this may seem an extremely simple operation, but he who has taught a child to put on gloves knows that this is by no means the case.

When our minds are much affected, so are the movements of our bodies.

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To those who admit the gradual evolution of species, a most striking instance of the perfection with which the most difficult consensual movements can be transmitted, is afforded by the hummingbird Sphinx-moth (Macroglossa); for this moth, shortly after its emergence from the cocoon, as shown by the bloom on its unruffled scales, may be seen poised stationary in the air, with its long, hair-like proboscis uncurled and inserted into the minute orifices of flowers; and no one, I believe, has ever seen this moth learning to perform its difficult task, which requires such unerring aim.

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A vulgar man often scratches his head when perplexed in mind; and I believe that he acts thus from habit, as if he experienced a slightly uncomfortable bodily sensation, namely, the itching of his head, to which he is particularly liable, and which he thus relieves. Another man rubs his eyes when perplexed, or gives a little cough when embarrassed, acting in either case as if he felt a slightly uncomfortable sensation in his eyes or windpipe.

From the continued use of the eyes, these organs are especially liable to be acted on through association under various states of the mind, although there is manifestly nothing to be seen. A man, as Gratiolet remarks, who vehemently rejects a proposition, will almost certainly shut his eyes or turn away his face; but, if he accepts the proposition, he will nod his head in affirmation and open his eyes widely. The man acts in this latter case as if he clearly saw the thing, and in the former case as if he did not, or would not, see it. I have noticed that persons in describing a horrid sight often shut their eyes momentarily and firmly, or shake their heads, as if not to see or to drive away something disagreeable; and I have caught myself, when thinking in the dark of a horrid spectacle, closing my eyes firmly.

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There are other actions which are commonly performed under certain circumstances, independently of habit, and which seem to be due to imitation or some sort of sympathy. Thus persons cutting anything with a pair of scissors may be seen to move their jaws simultaneously with the blades of the scissors. Children learning to write often twist about their tongues as their fingers move, in a ridiculous fashion. When a public singer suddenly becomes a little hoarse, many of those present may be heard, as I have been assured by a gentleman on whom I can rely, to clear their throats; but here habit probably comes into play, as we clear our own throats under similar circumstances.

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Reflex actions, in the strict sense of the term, are due to the excitement of a peripheral nerve, which transmits its influence to certain nerve-cells, and these, in their turn, excite certain muscles or glands261 into action; and all this may take place without any sensation or consciousness on our part, though often thus accompanied. As many reflex actions are highly expressive, the subject must here be noticed at some little length. We shall also see that some of them graduate into, and can hardly be distinguished from, actions which have arisen through habit. Coughing and sneezing are familiar instances of reflex actions.

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The conscious wish to perform a reflex action sometimes stops or interrupts its performance, though the proper sensory nerves may be stimulated. For instance, many years ago I laid a small wager with a dozen young men that they would not sneeze if they took snuff, although they all declared that they invariably did so; accordingly, they all took a pinch, but, from wishing much to succeed, not one sneezed, though their eyes watered, and all, without exception, had to pay me the wager.

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Dogs, when they wish to go to sleep on a carpet or other hard surface, generally turn round and round and scratch the ground with their fore-paws in a senseless manner, as if they intended to trample down the grass and scoop out a hollow, as, no doubt, their wild parents did, when they lived on open, grassy plains or in the woods.

THE PRINCIPLE OF ANTITHESIS.

Certain states of the mind lead, as we have seen in the last chapter, to certain habitual movements which were primarily, or may still be, of service; and we shall find that, when a directly opposite state of mind is induced, there is a strong and involuntary tendency to the performance of movements of a directly opposite nature, though these have never been of any service.

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When a dog approaches a strange dog or man in a savage or hostile frame of mind, he walks upright and very stiffly; his head is slightly raised, or not much lowered; the tail is held erect and quite rigid; the hairs bristle, especially along the neck and back; the pricked ears are directed forward, and the eyes have a fixed stare. These actions follow from the dog’s intention to attack his enemy, and are thus to a large extent intelligible. As he prepares to spring with a savage growl on his enemy, the canine teeth are uncovered, and the ears are pressed close backward on the head; but with these latter actions we are not here concerned. Let us now suppose that the dog suddenly discovers that the man whom he is approaching is not a stranger, but his master; and let it be observed how completely and instantaneously his whole bearing is reversed. Instead of walking upright, the body sinks downward or even crouches, and is thrown into flexuous movements; his tail, instead of being held stiff and upright, is lowered and wagged from side to side; his hair instantly becomes smooth; his ears are depressed and drawn backward, but not closely to the head; and his lips hang loosely. From the drawing back of the ears, the eyelids become elongated, and the eyes no longer appear round and staring. It should be added that the animal is at such times in an excited condition from joy; and nerve-force will be generated in excess, which naturally leads to action of some kind. Not one of the above movements, so clearly expressive of affection, are of the least direct service to the animal. They are explicable, as far as I can see, solely from being in complete opposition or antithesis to the attitude and movements which, from intelligible causes, are assumed when a dog intends to fight, and which consequently are expressive of anger.

ORIGIN OF THE PRINCIPLE OF ANTITHESIS.

We will now consider how the principle of antithesis in expression has arisen. With social animals, the power of intercommunication between the members of the same community—and, with other species, between the opposite sexes, as well as between the young and the old—is of the highest importance to them. This is generally effected by means of the voice, but it is certain that gestures and expressions are to a certain extent mutually intelligible. Man not only uses inarticulate cries, gestures, and expressions, but has invented articulate language; if, indeed, the word invented can be applied to a process completed by innumerable steps, half-consciously made. Any one who has watched monkeys will not doubt that they perfectly understand each other’s gestures and expression, and to a large extent, as Rengger asserts, those of man. An animal when going to attack another, or when afraid of another, often makes itself appear terrible, by erecting its hair, thus increasing the apparent bulk of its body, by showing its teeth, or brandishing its horns, or by uttering fierce sounds.

As the power of intercommunication is certainly of high service to many animals, there is no a priori improbability in the supposition that gestures manifestly of an opposite nature to those by which certain feelings are already expressed should at first have been voluntarily employed under the influence of an opposite state of feeling. The fact of the gestures being now innate would be no valid objection to the belief that they were at first intentional; for, if practiced during many generations, they would probably at last be inherited. Nevertheless, it is more than doubtful, as we shall immediately see, whether any of the cases which come under our present head of antithesis have thus originated.

With conventional signs which are not innate, such as those used by the deaf and dumb and by savages, the principle of opposition or antithesis has been partially brought into play. The Cistercian monks thought it sinful to speak, and, as they could not avoid holding some communication, they invented a gesture language, in which the principle of opposition seems to have been employed. Dr. Scott, of the Exeter Deaf and Dumb Institution, writes to me that “opposites are greatly used in teaching the deaf and dumb, who have a lively sense of them.” Nevertheless I have been surprised how few unequivocal instances can be adduced. This depends partly on all the signs having commonly had some natural origin; and partly on the practice of the deaf and dumb and of savages to contract their signs as much as possible for the sake of rapidity. Hence their natural source or origin often becomes doubtful, or is completely lost; as is likewise the case with articulate language.

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When a cat, or rather when some early progenitor of the species, from feeling affectionate, first slightly arched its back, held its tail perpendicularly upward and pricked its ears, can it be believed that the animal consciously wished thus to show that its frame of mind was directly the reverse of that when, from being ready to fight or to spring on its prey, it assumed a crouching attitude, curled its tail from side to side, and depressed its ears? Even still less can I believe that my dog voluntarily put on his dejected attitude and “hot-house face,” which formed so complete a contrast to his previous cheerful attitude and whole bearing. It can not be supposed that he knew that I should understand his expression, and that he could thus soften my heart and make me give up visiting the hot-house.

Hence, for the development of the movements which come under the present head, some other principle, distinct from the will and consciousness, must have intervened. This principle appears to be that every movement which we have voluntarily performed throughout our lives has required the action of certain muscles; and, when we have performed a directly opposite movement, an opposite set of muscles has been habitually brought into play—as in turning to the right or to the left, in pushing away or pulling an object toward us, and in lifting or lowering a weight.

THE PRINCIPLE OF THE ACTION OF THE EXCITED NERVOUS SYSTEM ON THE BODY.

The most striking case, though a rare and abnormal one, which can be adduced of the direct influence of the nervous system, when strongly affected, on the body, is the loss of color in the hair, which has occasionally been observed after extreme terror or grief. One authentic instance has been recorded, in the case of a man brought out for execution in India, in which the change of color was so rapid that it was perceptible to the eye.

Another good case is that of the trembling of the muscles, which is common to man and to many, or most, of the lower animals. Trembling is of no service, often of much disservice, and can not have been at first acquired through the will, and then rendered habitual in association with any emotion. I am assured by an eminent authority that young children do not tremble, but go into convulsions, under the circumstances which would induce excessive trembling in adults. Trembling is excited in different individuals in very different degrees, and by the most diversified causes—by cold to the surface, before fever-fits, although the temperature of the body is then above the normal standard; in blood-poisoning, delirium tremens, and other diseases; by general failure of power in old age; by exhaustion after excessive fatigue; locally from severe injuries, such as burns; and, in an especial manner, by the passage of a catheter. Of all emotions, fear notoriously is the most apt to induce trembling; but so do occasionally great anger and joy. I remember once seeing a boy who had just shot his first snipe on the wing, and his hands trembled to such a degree from delight that he could not for some time reload his gun; and I have heard of an exactly similar case with an Australian savage, to whom a gun had been lent. Fine music, from the vague emotions thus excited, causes a shiver to run down the backs of some persons.

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When animals suffer from an agony of pain, they generally writhe about with frightful contortions; and those which habitually use their voices utter piercing cries or groans. Almost every muscle of the body is brought into strong action. With man the mouth may be closely compressed, or, more commonly, the lips are retracted, with the teeth clinched or ground together.

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The heart will be all the more readily affected through habitual associations, as it is not under the control of the will. A man when moderately angry, or even when enraged, may command the movements of his body, but he can not prevent his heart from beating rapidly. His chest will, perhaps, give a few heaves, and his nostrils just quiver, for the movements of respiration are only in part voluntary. In like manner, those muscles of the face which are least obedient to the will will sometimes alone betray a slight and passing emotion. The glands, again, are wholly independent of the will, and a man suffering from grief may command his features, but can not always prevent the tears from coming into his eyes. A hungry man, if tempting food is placed before him, may not show his hunger by any outward gesture, but he can not check the secretion of saliva.

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With all, or almost all, animals, even with birds, terror causes the body to tremble. The skin becomes pale, sweat breaks out, and the hair bristles.

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A physician once remarked to me, as a proof of the exciting nature of anger, that a man when excessively jaded will sometimes invent imaginary offenses, and put himself into a passion, unconsciously, for the sake of reinvigorating himself; and, since hearing this remark, I have occasionally recognized its full truth.

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Exertion stimulates the heart, and this reacts on the brain, and aids the mind to bear its heavy load.