A skilled movement is impossible in the absence of guiding sensations. I decide to button my coat. Sensation-paths from the muscles of the forearm are opened into motor paths extending from the large pyramids in the arm-centres of the kinæsthetic cortex. But it is not sufficient that the action be started: it must be guided by the sensations which movement produces. If my fingers are numb with cold, I cannot button the coat. The muscles which move the fingers are warm enough beneath the sleeve, but my attempts to will them to move are as futile as they would be if the muscles belonged to some other person. The will has no power over the muscles. It is essential that the sensations which accompany the act of buttoning the coat flow through the same paths as hitherto in the cortex of the brain. Flowing through the same paths, they produce the same effect in consciousness, the same perceptions. In ordinary parlance, one cannot perform any act unless one can remember what it felt like to perform it on a previous occasion. It is almost as sound physiology to describe the voluntary action of fastening a button as commencing in the skin of the fingers as to describe is as commencing in the brain. The act is due to the direction of attention to impulses which flow from muscle to muscle, and from skin to muscle.
All skill in the use of muscles is acquired by the method of trial and error. Familiar movements are tried, combined, modified with a view to the production of a new result. A man accustomed to striking with the right hand forwards endeavours to swing a golf-club with the left hand backwards. For a long time the result is anything but a success. At length the head of the club takes the right curve. It not only hits the ball with its centre, but it carries it through in the right line. The ball travels 120 yards or so towards the green. In golfing terminology, a successful drive is always “an awful fluke”; but the fluke once accomplished, nothing is easier for the golfer than to drive equally well on all succeeding occasions. He need merely remember exactly what it felt like to give the club a perfect swing, and exclude all other sensations while he is passing these memories through his sensori-motor arcs!
The fact that we can deliberately improve an action, fitting it to the attainment of the object of desire, by suppressing wrong and emphasizing right sensations, shows how large a part consciousness plays in the affairs of the nervous system. This brings us to the frontier of physiology. At this boundary the authority of the physiologist ends. He cannot define consciousness; he cannot investigate it. Yet he naturally asks whether the machine which he is investigating is a machine and nothing more. When the possibilities of reflex action were first recognized, thought tended to dethrone feeling and Will in favour of automatism. If the actions of a spinal frog exhibit so distinct a purposive character, why, it was asked, should we assume that the frog with a brain is anything more than a reflex machine? Light, heat, sound are playing upon its sense-organs; surely these stimuli suffice to set going all the sensori-motor currents which lead to the various movements which in their totality constitute the frog’s behaviour! And why assign to a mammal a self-directing authority which we deny to a frog? The increased complexity of its behaviour is more than accounted for by the greater variety of its nervous arcs. All animals, it was argued, including Man, are reflex machines. Their thoughts and actions are the effects of the play upon their nervous systems of forces from the outer world. Each inherits a nervous system of a certain pattern. Its individual development is conditioned by the sensations which pass through it. The sensations are impressed by the environment. Therefore the individual is a puppet, his activities the dance of circumstance. Consciousness is an “epiphenomenon.” Few physiologists or students of animal behaviour take this material view of life at the present day. The fact that it leads inevitably to the conclusion that consciousness is an “epiphenomenon” (Huxley’s term) is its reductio ad absurdum. It is not in harmony with the economy of Nature that an animal should be endowed with the capacity of feeling pain and pleasure, if such endowment is useless to it. It can be useful only by directing activity towards the attainment of pleasure and the avoidance of pain. This admitted, the mechanical theory falls to the ground. There is an “It” which feels, selects feelings, chooses those which have a pleasant tone, wills to perform the acts by which they are attained. It follows that the value of consciousness lies in the prerogative which it confers of adapting action, within certain limits, to circumstance. An animal succeeds in life in proportion as the nervous system which it inherits reacts satisfactorily to its environment. A chick which, after being hatched in an incubator, has been isolated for twelve hours without food, seizes a grain of corn the instant that it sees it. Its brain contains ready-made sensori-motor arcs connecting the spot in its cortex in which the visual impression of the grain is perceived and the motor neurones which control the pecking muscles. A sheep-dog is quickly broken to sheep, because its ancestors have been selected by mankind from amongst dogs that readily adapted themselves to this work. The breeder has selected a pattern of brain with the same success with which, when appearance is the only desideratum, he selects a pattern of coat. Beavers set to work at constructing a dam at the only spot in a valley at which it is possible to create an artificial lake, because for countless ages Nature has ruled out the animals which constructed their dams in unsuitable places. Man also inherits a brain-pattern; but, not being required to shift for himself soon after birth, he goes through a long period of infancy and tutelage, during which, by force of circumstance and his own Will, the pattern is elaborated. His supreme success is due to his capacity for adapting means to ends. He inherits very few instincts. Except as regards organic functions, his spinal cord is subservient in almost all respects to his brain. Most of the actions of an animal are instinctive—a word which has been sadly misapplied. Its connotation is negative rather than positive. Owing to the marked pattern of its brain, an animal finds it difficult to avoid acting in a particular way. As the nights grow longer and its hours for feeding are curtailed, a swallow is impelled by its instinct to go South. It makes the same use of its sensations during its migration, and is as completely dependent upon them for its guidance as a man would be. The lower we descend the scale, the more inevitable do an animal’s movements become; but there can be no doubt but that consciousness is of value to an animal, as to Man, in that it gives to its individuality the capacity, within such limits as Nature has selected, of resisting or modifying its ancestral instincts when they are not absolutely appropriate to the occasion.
Sentience implies personality. “No system of philosophy can extrude the ego.” The difference between the performance of the animal machine as a physiologist studies it, and its behaviour when under the control of its own driver, is the difference between reflex action and choice. The ego interacts with physical forces. It does not come within the province of the physiologist to explain the source of the force which interferes with force. He finds no trace of it on either credit or debit side when making up the body’s accounts. He is unable to enter, “Item, to the development of consciousness ... so much.” He can form no conception of this immaterial manifestent which hovers over the infinitely numerous sensori-motor exchanges which are always occurring in the cortex of the brain, giving to a particular group of agitations, now here, now there, a special quality; but the manifestent is needed to account for the potency of the reinforced agitations which enables them to take possession of the nerve-paths by which muscles are reached.
It is for the psychologist to define the application of the terms “consciousness,” “attention,” “will.” He cannot define the attributes of the ego which these terms connote. The moralist must show the way in which they determine, or should determine, conduct. Yet within the plain limits of physiology, attention, using the word in its every-day sense, modifies the responses of the nervous system in a degree which cannot escape observation. It is astonishing to anyone accustomed to hospital surgery (although even in this field singular exceptions are met with) to see the grave operations which a veterinary surgeon may perform, without the animal showing any evidence of pain, provided its apprehension has not been aroused and its attention directed to what is being done. A horse standing in front of a crib of oats, untied, will hardly whisk its tail while the surgeon is making a great wound in its flesh, and sawing off a bony excrescence. The knife does not come within the experience of a horse. It has no anticipations, and its skin, intensely sensitive to the tickling of a fly or the smart of a whip, is relatively insensitive to a cut. An eminent surgeon of the last generation (the writer, as a student, “dressed” for him in his old age) was in the habit, having arranged that his patient could not see what he was doing, of performing operations of a very painful nature whilst assuring his patient, “I am merely making a thorough examination, in order that I may be perfectly certain of the cuts that I shall have to make to-morrow in the operating-theatre when you are under chloroform.” We are not concerned with the ethics of his method; but the assurance, “Now that’s all over; you will never need to have that operation performed again,” saved many a sufferer from a night of apprehension and a miserable “coming round.”
It was stated, during the South African War, that at Ladysmith the bearer of a critical despatch, who was struck in the palm of the hand by a bullet which traversed the whole length of his forearm, did not discover that he was wounded until he saw the dripping blood, after his errand was successfully accomplished. To deliberately cut oneself with a razor is most painful, yet shaving in the morning, with thoughts concentrated on the doings of the day, it is often the sight of blood which directs attention to the fact that the skin is severed. Of all evidences of self, the power of paying attention is the most noteworthy. We can direct attention to certain sensations, which then become perceptions, and we can deliberately ignore others, within certain restricted limits.
The control of the nervous apparatus by the self is a truth which no student of the physiology of human beings can ignore. Isolated from its relation to all other scientific truths, it has been made the basis of a nescience which, although positively merely foolish, is, negatively, harmful—yet a form of folly which answers well to the needs of persons of a certain category.
It may be objected that the picture of the relation of mind to brain which is here presented—the one, activity, motion, the other a labyrinth of conducting paths—makes all mental phenomena entirely dependent upon current sensations. No results could happen if the sensations were not there. It affords no ground for the explanation of mental images, hallucinations, dreams. A few lines may be spared to show that this objection does not hold. We cannot attempt to explain the conscious control of thought. It is a part of the impenetrable mystery to which we have just referred. But, granted that it obtains, the direction by the ego of afferent nerve-currents through the same strands which formerly vibrated to sensations which drew a picture, and hence the revival of its image, is no more incomprehensible than the liberation of afferent impulses from muscles into efferent channels. Brain-chains are composed of many links. Their interconnection is illimitable. When I recall the appearance of the house in which I lived as a child, I throw into the chain impulses (from somewhere) which traverse the final links, where passage implies consciousness. At the edge of the lace-work of linked threads the impulses light up a pattern which childhood’s experience worked into the apparatus of thought.
If we were to admire the perfection of any special aspect of the brain’s functioning, the rarity of hallucinations might give us cause for wonder. That impulses so seldom leave their own paths is more astonishing than that occasionally, when the brain is excited and its nutritive conditions deranged, the impulses which the ego can direct into channels where they revive an image should sometimes, and with far greater force, make their own way down well-worn paths, lighting up a picture which deceives the ego. Dreams, by contrast, throw up in a strong light the part played by attention in intelligent life. The capacity for alertness is due to the favouring of one set of impulses by suppressing others. The favoured impulses hold the road. Concentration of attention is keeping thought to one line by resisting all temptation to wander into by-paths. The waking condition is the state in which all nerve-ways are closed, with the exception of those which consciousness is using. The more severe the closure, the more vivid is consciousness. In sleep all paths are open. In none is the potential acquired by impulses in the process of overcoming resistance high enough to evoke consciousness. A burst of impulses ascends from the stomach, set a-flowing by undigested fragments of salmon and cucumber, or mounts from the arm on which the sleeper has been lying until its circulation has been arrested. They reverberate through the open corridors of the brain. If they are sufficiently noisy to awaken the sleeper, he, detecting them in this path and in that, supposes them to be on the same errands as the impulses which commonly pass thus. If dreams are analysed, it will be found that, although the combinations of impressions may be uncommon and extremely bizarre, the impressions are selected from the most familiar. The images of which the dream is compounded, which may have lost all normal relations and may have assumed impossible proportions, are those which the mind most frequently conjures up. In the large majority of instances some happening of the day preceding can be recognized as the prompting cause. A remembered dream is the photograph taken by consciousness of the sensations which have bombarded it into activity. Especially if due to impulses originated by visceral discomfort, the dream may have an unpleasant tone. This may take various forms, but the emotion most commonly aroused is fear. The objects visualized may have preposterous dimensions, or they may be not sufficiently distinct for recognition—elusive imps; but most commonly distress is caused by the want of harmony of sensations, due to the absence of kinæsthetic elements. A man is lying on the railway-line; a train is approaching with increasing speed; he cannot get up. He is in the pulpit, but cannot speak. Dreams thus confirm the view set forth above as to the cause of volitional action. Ability to perform an act depends upon the flow through the kinæsthetic centres of the brain of impulses generated in the muscles by which the act is to be, or is being, performed. Kinæsthetic sensations do not under any circumstances play the same part in mental life as sensations from the skin, the eye, or the ear; when the body is passive in bed they are not flowing into the cortex. The dream-photograph shows elements demanding movement, but affords no evidence that movement is in progress.