Popular Science Monthly/Volume 52/February 1898/The Evolution of the Mind
|THE EVOLUTION OF THE MIND.|
PRESIDENT OF LELAND STANFORD JUNIOR UNIVERSITY.
THE mind, in the sense in which I shall here use the word, is the collective function of the sensorium or brain of man and animals. It is the sum total of all psychic changes, actions, and reactions. Under the head of psychic functions are included all operations of the nervous system, as well as operations of like nature which take place in creatures without specialized nerve fibers or nerve cells.
As thus defined, mental operations are not necessarily or exclusively conscious. With the lower animals nearly all of them are automatic and unconscious. Even with man, most of them must be so. But between the automatic and the conscious actions no sharp line of division exists. All functions of the nervous system are alike in nature, and from the present point of view may be considered together. Consciousness is not an entity, but a condition. It stands related to mind much as flame is related to fire.
It is a recognized law in biology that "function precedes structure." To define this law more exactly, we should say that function precedes the differentiation of the organ on which it depends. There is a certain work to be done, and a certain body of cells are set apart sooner or later to do it. Just as plowing was done in some fashion before the invention of the plow, so in some manner respiration was accomplished before the development of gills and lungs. Something of mental action came before there was ever an organized brain.
In the animals of one cell, or protozoa, breathing and digestion are each performed by the whole body. In the division of labor or specialization which arises in the higher or many-celled animals, certain alliances of cells or tissues are set apart for respiration alone, and certain others for digestion, while other functions of animal life are relegated to still other cell alliances. Each organ in turn is released from all functions except its own.
Irritability, or the response to external stimulus, is an attribute of all living organisms. In the method and degree of response variations occur. These variations favorable to the division of labor and the adaptation of the animal to its surroundings are seized and fixed by natural selection. In this way, on the basis of a diffused function, an organ is built up and the organ itself is specialized and perfected.
The mind and consciousness of man grow out from the irritability of the lower animals. They are developed through series of successive differentiations and integrations. All the higher animals are colonies of co-operating and co-ordinated cells. In such colonies of units the functions of sensation, thought, and motion are relegated to series of the most sensitive and most highly organized cells. This alliance of cells is adequate for the work it has to perform. The brain is always adequate for the mind, for the one is the organ, the other the function, and the development of the two must go on together.
The intellect of man can not be regarded as the crowning marvel of the "great riddles of life." A marvel is no greater for its bigness. Life is one continuous marvel, without break or end. The human mind is one of life's manifestations. The marvel appears in great or small psychic powers alike, for the great powers of the many-celled brain are produced by the co-operation and specialization of the small powers of the single cell. Nature knows neither great nor small. "God works finer with his hands than man can see with his eyes." The single cell is far from simple. The egg or germ cell carries within itself the whole machinery as well as the whole mystery of heredity. The simplest organism we know is far more complex than the Constitution of the United States. Its adjustments, checks, and balances are more perfect. It should in its changing relations be compared rather with the great unwritten constitution of civilized society. The laws of society spring from the laws governing the development of the single cell. If we knew the latter "all in all," as Tennyson says of the flower, "we should know what God is and man is."
If we could know all of any life problem to its uttermost detail, we should have the clew to all life.
Among the protozoa, as already stated, all activities are centered in the single cell which forms the animal unit. Each cell is sufficient unto itself. It is independent and free, but it is at the same time unspecialized and ineffective. Its career offers no scope for volition, for a single life unit can not control the elements which surround it. It is the sport of the wind and the wave. But the recognition of self and non-self, which in one form or another is the attribute of all life, is not wanting among the protozoa. Some of them develop this sense to a large degree. It is said that among the rhizopods are those whose appendages or pseudopodia are at once cast off if they come in contact with the appendages of another of the same species. This recognition of self and non-self is not intellect, but it is homologous with the impulses on which in the higher types personality depends.
All sensation has reference to action. If a creature is not to act, it can not feel. Wherever motion exists there is some sensitiveness to external conditions, and this is of the nature of mind. In a compound organism the nature and position of the sensorium or mind center depend on what it has to do, or rather on what were the duties the same structure had to perform in the life of the creature's ancestors.
A plant may be defined as a sessile animal. It is an organic colony of cells, with the power of motion but not that of locomotion. The plant draws its nourishment from inorganic Nature—from air and water. Its life is not conditioned on a search for food, or on the movement of the body as a whole.
The plant searches for food by a movement of the feeding parts alone. In the process of growth, as Darwin has shown, the tips of the branches and roots are in constant motion. This movement is in a spiral squirm. It is only an exaggeration of the same action in the tendrils of the growing vine. The course of the squirming rootlet may be deflected from a regular spiral by the presence of water. The moving branchlets will turn toward the sun. The region of sensation in the plant and the point of growth are identical, because this is the only part that needs to move. The tender tip is the plant's brain. If locomotion were in question, the plant would need to be differently constructed. It would demand the mechanism of the animal. The nerve, brain, and muscle of the plant are all represented by the tender growing cells of the moving tips. The plant is touched by moisture or sunlight. It "thinks" of them, and in so doing the cells that are touched and "think" are turned toward the source of the stimulus. The function of the brain, therefore, in some sense exists in the tree, but there is no need in the tree for a specialized sensorium.
The many-celled animals, from the lowest to the highest, bear in their organization some relation to locomotion. The animal feeds on living creatures, and these it must pursue if it is to thrive. It is not the sensitive nerve tips which are to move; it is the whole creature. By the division of labor, the whole body of the compound organism can not be given over to sensation. Hence, the development of sense organs different in character, one stimulated by waves of light, another by waves of sound; one sensitive to odor, another to taste; still others to contact, temperature, muscular strain, and pain. These sense organs through their nerve fibers must report to a sensorium, which is distinct from each one of them. And in the process of specialization the sensorium itself is subdivided into higher and lower nerve centers—centers of conscious thought and automatic transfer of impulse into motion. This transfer indicates the real nature of all forms of nerve action. All are processes of transfer of sensation into movement. The sensorium or brain has no knowedge except such as comes to it from the sense organs through the ingoing or sensory nerves. It has no power to act save by its control of the muscles through the outgoing or motor nerves. The mind has no teacher save the senses; no servants save the muscles.
The reflex action, then, is the type of all mental operations. The brain is hidden in darkness, protected from sensation, as also from injury, by a bony box or a padding of flesh. It has no ideas of its own. It can receive no information directly. But the sense organs flood it with impressions of the external world. From the body itself, by similar means, are transmitted impulses to action. Such impulses in all animals and men are transmitted from generation to generation as a part of the legacy of heredity. They are in their nature rather methods than impulses. Movements go along lines of least resistance, and such lines are part of the stock of heredity.
Many of the impressions from environment are received by the lower nerve centers alone, the sympathetic system or the spinal cord. Here they are converted at once into motion without rising into the region of consciousness. Other sensations rise to the brain itself, and are made the basis of voluntary and conscious action. And between the purely automatic actions and those distinctly conscious and voluntary there may be found every possible intermediate grade.
Moreover, a conscious action often repeated becomes in some degree reflex and automatic. By repeated action nerve connections are formed, which have been compared to the automatic switches of the electric-light plant. By these connections an action once become familiar requires no further attention. This fact is known to us as the formation of habit. That which we do to-day voluntarily and even laboriously, the force of habit will cause us to repeat to-morrow easily, involuntarily, and whether we will or not. By the repetition of conscious actions the character is formed. This formation of personal character by action I have called "the higher heredity," as distinguished from the true heredity which finds its bounds in the content of the germinal cell. By means of habits each creature builds up in some fashion its own life. In such way and to some degree each is "the architect of his own fortunes." In such manner "the vanished yesterdays" are the rulers of to-morrow.
Besides the actual sensations, besides the so-called realities, the brain retains also the sensations which have been, and which are not wholly lost. Memory pictures crowd the mind, mingling with pictures brought in afresh by the senses. The force of suggestion causes the mental states or conditions of one person to repeat themselves in others. Abnormal conditions of the brain itself furnish another series of feelings with which the brain must deal. Moreover, the brain is charged with impulses to action passed on from generation to generation, surviving because they are useful. With all these arises the necessity for choice as a function of the mind. The mind must neglect or suppress all sensations which it can not weave into action. The dog sees nothing that does not belong to its little world. The man in search of mushrooms "tramples down oak trees in his walks." To select the sensations that concern us is the basis of the power of attention. The suppression of undesired action is a function of the will. To find data for choice among the possible motor responses is a function of the intellect. Intellectual persistency is the essence of individual character.
As the conditions of life become more complex, it becomes necessary for action to become more carefully selected. Wisdom is the parent of virtue. Knowing what should be done logically precedes doing it. Good impulses and good intentions do not make actions safe. In the long run, action is tested not by its motives but by its results.
The child, when he comes into the world, has everything to learn. His nervous system is charged with tendencies to reaction and impulses to motion, which have their survivals from ancestral experience. Exact knowledge, by which his own actions can be made exact, must come through his own experience. The experience of others must be expressed in terms of his own before it becomes wisdom. Wisdom, as I have elsewhere said, is knowing what it is best to do next. Virtue is doing it. Doing right becomes habit if it is pursued long enough. It becomes a "second nature," or, we may say, a higher heredity. The formation of a higher heredity of wisdom and virtue, of knowing right and doing right, is the basis of character-building.
The moral character is based on knowing the best, choosing the best, and doing the best. It can not be built up on imitation. By imitation, suggestion, and conventionality the masses are formed and controlled. To build up a man is a nobler process, demanding materials and methods of a higher order. The growth of man is the assertion of individuality. Only robust men can make history. Others may adorn it, disfigure it, or vulgarize it.
The first relation of the child to external things is expressed in this: What can I do with it? What is its relation to me? The sensation goes over into thought, the thought into action. Thus the impression of the object is built into the little universe of his mind. The object and the action it implies are closely associated. As more objects are apprehended, more complex relations arise, but the primal condition remains—What can I do with it? Sensation, thought, action—this is the natural sequence of each completed mental process. As volition passes over into action, so does science into art, knowledge into power, wisdom into virtue.
It is thus evident that, with an animal as with an army, locomotion demands direction. The sensorium is built up as a director of motion. Natural selection causes the survival of those whose senses are adequate for the safe control of movement. The animal which conducts its life processes in insecurity perishes. The existence of an organism is the test of its adequacy. The continued existence of a series of organisms is the ultimate proof of the truth of the senses.
With the lower animals we have automatic obedience to the demand of external conditions. The greater the stress of the environment the more perfect the automatism, for impulses to safe action must always be adequate for the duty which in the ancestral past they have had to perform. To automatic mind processes inherited from generation to generation the name instinct has been given. Whether instinct is in any degree "inherited habit" or whether it is the product simply of natural selection acting upon the varying methods of automatic response destroying those whose responses are inadequate, need not concern us now.
The homing instinct of the fur seal, concluding its long swim of three thousand miles by a return on a little island hidden in the arctic fogs, to the very spot from which it was driven by the ice six months before, excites our astonishment. But this power is not an illustration of animal intelligence. The homing instinct with the fur seal is a simple necessity of life. Without it the individual would be lost to its species. Only those which have the instinct in perfection can return; only those who return can leave descendants. As to the others, the rough sea tells no tales. We know that not all of the fur seals who set forth return. To those who do return the homing instinct has proved adequate. And this it must always be, so long as the race exists, for general inadequacy would mean extinction of the species.
The intellect, as distinguished from lower mental operations, is the choice among responses to external conditions. Complex conditions permit a variety of responses. Varying conditions demand a change of response. This demand is met by the intellect. The intellect rises with a complex or changing environment. The greater the stress on a race of thinking creatures, the more active and effective their thoughts. The growth of man has been a succession of triumphs over hard conditions. The races which have been successful have arisen from adversity. Prosperity has been the conquest of hard times. Human progress in general has come through the falling away of the ineffective. The "fool-killer" has been its most active agent. "The goodness and the severity of God" are in science one and the same thing, as they were in the thought of the prophet. Its essence is the survival of those who can live and act effectively and happily in the conditions which surround human and animal life. The power of safe and accurate response to external conditions is the essential feature of sanity. The inability to adapt action to need is a character of insanity. Insanity, except as protected by human altruism, means death.
The difference between intellect and instinct in lower animals may be illustrated by the conduct of certain monkeys brought into relation with new experiences. At one time I had two adult monkeys, "Bob" and "Jocko," belonging to the genus Macacus. Neither of these possessed the egg-eating instinct. At the same time I had a baby monkey, "Mono," of the genus Cercopithecus. Mono had never seen an egg, but his inherited impulses bore a direct relation to feeding on eggs, as the heredity of Macacus taught the others how to crack nuts or to peel fruit.
To each of these monkeys I gave an egg, the first that any of them had ever seen.
The baby monkey, Mono, being of an egg-eating race, devoured his eggs by the operation of instinct. On being given the egg for the first time, he cracked it against his upper teeth, making a hole in it, sucked out all the substance, then, holding the eggshell up to the light and seeing that there was no longer anything in it, he threw it away. All this he did mechanically, automatically, and it was just as well done with the first egg he ever saw as with any other he ate. All eggs since offered him he has treated in the same way.
The monkey Bob took the egg for some kind of nut. He broke it against his upper teeth and tried to pull off the shell, when the inside ran out and fell on the ground. He looked at it for a moment in bewilderment, and then took both hands and scooped up the yolk and the sand with which it was mixed, and swallowed it all, and then stuffed the shell itself into his mouth. This act was not instinctive. It was the work of pure reason. Evidently his race was not familiar with the use of eggs. Reason is an inefficient agent at first, a weak tool; but when it is trained it becomes an agent more valuable and more powerful than any instinct.
The monkey Jocko tried to eat the egg offered him in much the same way that Bob did, but, not liking the taste, he threw the whole thing away.
The low intelligence of the lower animals—as the fishes—may be at times worse than none at all. If mental development were a real advantage to fishes it would take place through natural selection. The fishes taken in a large pound net, as I have observed them in Lake Michigan, can not escape from it because they have not intelligence enough to find the opening through which they have entered. If, however, a loon enters the net, the fishes become frightened and "lose their heads." In this case they will sooner or later all escape, for they cease to hunt about ineffectively for an opening, but flee automatically in straight lines, and these straight lines will in time bring them to the open door of the net.
Wild animals learn to avoid poisonous plants by instinct. Those who have not an inherited dislike for these plants perish. When the animals are brought into contact with vegetation unknown to their ancestors, this instinct fails them. Hence arises in California the danger from "loco weeds," as certain species of wild vetches are called. These plants produce temporary or permanent insanity or paralysis of nerve centers. The native ponies avoid them, but imported animals do not, and often fall victims to their nerve-poisoning influence.
The confusion of highly perfected instinct with intellect is very common in popular science. The instinct grows weak and less accurate in its automatic obedience as the intellect becomes available in its place. Both intellect and instinct are outgrowths from the simple reflex response to external conditions. But the instinct insures a single definite response to the corresponding stimulus. The intellect has a choice of responses. In its lower stages it is vacillating and ineffective; but as its development goes on it becomes alert, and adequate to the varied conditions of life. It rises with the need for improvement. It will therefore become impossible for the complexity of life to outgrow the adequacy of man to adapt himself to its conditions.
Many animals currently believed to be of high intelligence are not so. The fur seal, just mentioned, for example, finds its way back from the long swim of two or three thousand miles through a foggy and stormy sea, and is never too late or too early in his arrival. In like manner the female fur seal goes two hundred miles to her feeding grounds in summer, leaving the pup on the shore. After a week or two she returns to find him within a few rods of the rocks where she had left him. Both mother and young know each other by call and by odor, and neither are ever mistaken though ten thousand other pups and other mothers occupy the same rookery. But this is not intelligence. It is simply instinct, because it has no element of choice in it. Whatever its ancestors were forced to do, the fur seal does to perfection. Its instincts are perfect as clockwork, and the necessities of migration must keep them so. But if brought into new conditions it is dazed and stupid. It has no choice among different lines of action.
The Bering Sea Commission once made an experiment on the possibility of separating the young male fur seals from the old ones in the same band. The method was to drive them through a wooden chute or runway with two valvelike doors at the end. These animals can be driven like sheep, but to sort them in this way is impossible. The most experienced males will beat their noses against a closed door, if they have seen one before them pass through it. That this door had been shut, and another beside it opened, passes their comprehension. They can not choose the new direction. In like manner a male fur seal will watch the killing and skinning of his mates with perfect composure. He will sniff at their blood with languid curiosity. "So long as it is not his own it does not matter." That it may be his own in a minute or two it is beyond his power to foresee.
The study of the development of mind in animals and men gives no support to the mediæval idea of the mind as an entity apart from the organ through which it operates.
The "Clavier theory" of the mind, that the ego resides in the brain, playing upon the cells as a musician upon the chords of a piano, finds no warrant in fact. There is no ego except that which arises from the co-ordination of the nerve cells. All consciousness is "colonial consciousness," the product of co-operation. It stands related to the action of individual cells much as the content of a poem with the words or letters composing it. Its existence is a phenomenon of co-operation. The I in man is the expression of the co-working of the processes and impulses of the brain. The brain is made of individual cells, just as England is made of individual men. To say that England wills a certain deed, or owns a certain territory, or thinks a certain thought, is no more a figure of speech than to sav that "I will," "I own," or "I think." The "England" is the expression of union of the individual wills, thoughts, and ownerships of Englishmen. Similarly, my "ego" is the expression of the aggregate force co-ordination of the elements that make up my body.
The old dictum of the philosopher, "I think, therefore I am," is not literally and wholly true. "We think, therefore we are," we co-ordination of brain cells, would be quite as rational. But we brain cells do not think individually, only collectively or colonially, so no single sentence can express the whole truth, nor can a trustworthy philosophy grow out of any axiom of this sort.
The development of the character is the formation of the ego. It is in itself the co-ordination of the elements of heredity, the bringing into union of the warring tendencies and irrelevant impulses left us by our ancestors. The child is a mixture of imperfectly related impulses and powers. It is a mosaic of ancestral heredity. Its growth into personality is the process of bringing these elements into relation to each other.
In a remarkable study of the phenomena of "conversion," Mr. Edwin Diller Starbuck gives this view of the physiological phenomena associated with the development of personality, the building up of a self by a process which is primarily unselfing": "It is pretty well known," Mr. Starbuck says, "that the quality of mind is much dependent upon the fineness of nervous structure. The child has about as many nerve cells as the adult. They differ from those of the adult in form. Those of the child are mostly round, whereas those of the adult have often very many branches with which they connect with the other cells. Nervous growth seems to consist largely in the formation of new nervous connections. The rapid growth at puberty probably means that at that time there is a great increase in nervous branching. The increased ramification of nervous tissue probably determines the ability for seeing in general terms, for intellectual grasp, and for spiritual insight. The rapid formation of new nerve connections in early adolescence may be the cause of the physiological unrest and mental distress that intensifies into what we have called the sense of incompleteness which precedes conversion. The mind becomes a ferment of half-formed ideas, as the brain is a mesh of poorly organized parts. This creates uncertainty, unhappiness, dejection, and the like, because there is not the power of free mental activity. The person is restless to be born into a larger world that is dimly felt. Finally, through wholesome suggestions or normal development, order comes and the new world dawns. Often some emotional stress or shock strikes harmony into the struggling imperfection, and truth comes like a flash."
The evil effect of the excess of sense impressions and of thought dissociated from will and action has been noted many times and in many ways. When men have made themselves wise with the lore of others, the learning which ends in self and does not spend itself on action, they have been neither virtuous nor happy. "Much learning is a weariness of the flesh." Thought without action ends in intense fatigue of the soul, the disgust with all "the sorry scheme of things entire," which is the mark of the unwholesome and insane philosophy of pessimism. This philosophy finds its condemnation in the fact that it has never yet been translated into pure and helpful life.
In like manner has sentiment not woven into action failed to be a source of effectiveness or of happiness. "If thou lovest me," said Christ to Simon Peter, then shalt thou "feed my lambs." Genuine love works itself out in self-spending, in doing something for the help or pleasure of those beloved. Religious sentimentalism, whatever form it may take, if dissociated from action, has only evil effects. Appeals to the emotions for emotion's sake have been a great factor in human deterioration. Much that has been called "degeneration" in modern social life is due to the predominance of sensory impressions over motor movement. The mind passes through a round of sensations, emotions called up by literature, music, art, religion, none of these having any direct bearing on human conduct. Their aggregate influence on the idle soul is always an evil one. And the misery of motor paralysis, of intellectual pauperism, is felt as the disease of ennui. The remedy for evils of reverie, ennui, narcotism, and the like, is to be found in action. The knowledge of this fact constitutes the strength of the Salvation Army movement. The victim of mental deterioration is given something to do. He is not to wear out the little force he has in ineffective remorse. Better let him beat a big drum and make night hideous with unmusical song than to settle down to the dry rot of reverie or the wet rot of emotional regret. Something to do, and the will to act, furnish the remedy for all forms of social discontent.
Not every sense impression needs a distinct response. It is the function of the intellect to sift these impressions, turning over into action only those in which action is desirable or wise. The power of attention is one of the most valuable attributes of the trained mind; and the essential of this power is in the suppression by the will of all impulses which do not concern the present need of action.
As the normal workings of the mind are reducible to sensation, thought, will, and action, so the abnormal workings may be due to defects of any one of these elements. We may have defects of sensation, defects of thought, vacillation of will, and inaccuracy of action. Hyperæsthesia, anæsthesia, sensory weakness, appear in the uncertain action of the muscles guided by the ill-informed brain. The defects and diseases of the brain itself show themselves in many ways, ranging from oddity or folly to the extreme of idiocy or mania. Most of the "psychic phenomena" along "the border land of spirit," which occupy a large part in current discussions, are characters of insanity. The phenomena of hysteria, faith-cure, openness to suggestion, subjective imagery, mysticism, are not indications of spiritual strength, but of decay and disintegration of the nerves. The ecstasy of unbalanced religious excitement and a stupor of a drunken debauch may belong to the same category of mental phenomena. Both point toward moral and spiritual decay. There are no occult or "latent powers" of the mind except those which have become useless or which belong to the process of disintegration. If a man crosses his eyes, and is thus enabled to see objects double, we do not regard him as having developed a "latent power" of vision. He has simply destroyed the normal co-ordination of such powers. In like manner, one does not increase the strength of a rope by untwisting its many strands. The effectiveness of life depends upon the co-ordination and co-operation of the parts of the nervous system. Its strands must be kept together. To move in a state of reverie, "to live in two worlds at once," to be unable to separate memory pictures from realities, all these are forms of nervous disintegration. Every phase of them can be found in the madhouse. The end of such conditions is death. The healthy mind should combat all tendencies toward disintegration. It can be clean and strong only by being true.
In like manner the influence of all drugs which affect the nervous system must be in the direction of disintegration. The healthy mind stands in clear and normal relations with Nature. It feels pain as pain. It feels action as pleasure. The drug which conceals pain or gives false pleasure when pleasure does not exist, forces a lie upon the nervous system. The drug which disposes to reverie rather than to work, which makes us feel well when we are not well, destroys the sanity of life. All stimulants, narcotics, tonics, which affect the nervous system in whatever way, reduce the truthfulness of sensation, thought, and action. Toward insanity all such influences lead; and their effect, slight though it be, is of the same nature as mania. The man who would see clearly, think truthfully, and act effectively, must avoid them all. Emergency aside, he can not safely force upon his nervous system even the smallest falsehood. And here lies the one great unanswerable argument for total abstinence; not abstinence from alcohol alone, but from all nerve poisons and emotional excesses. The man who would be sane must avoid all nerve excitants, nerve soothers, and "nerve foods," as well as trances, ecstasies, and similar influences. If he would keep his mind he must never "lose his head" save in the rest of normal sleep.
No great work was ever accomplished under the influence of drugs or stimulants. The great thoughts and great works which have moved the world came from men who have lived pure, sober lives. These were men whose nervous systems were truthful as the stars, and the great truths of the universe they could carry over into action.
What is true of man is true of animals, and true of nations as well; for a nation is an aggregation of many men as a man is a coalition of many cells. In the life of a nation, Lowell tells us, "three roots bear up Dominion—Knowledge, Will, the third Obedience, the great tap-root of all." This corresponds to the nervous sequence in the individual. And as in general the ills of humanity are due to untruthfulness in thought and action, so are the collective ills of nations due to national folly, vacillation, and disobedience. The laws of national greatness are extensions of the laws which govern the growth of the single cell.