An Introduction to Comparative Psychology
Chapter 11: Automatism and Control
C. Lloyd Morgan
WE have already learnt that from all parts of the surface of the body,-from eye, ear, nose, and palate, from the muscles, joints, and internal viscera,--there run nerves-- ingoing or afferent nerves-- which are in direct connection with the spinal cord and the brain. These nerves are the channels along which impulses may be transmitted to the nerve-centres. Within these nerve-centres molecular disturbances are thereby caused, as the result of which further impulses are transmitted down other nerves -- outgoing or efferent nerves-to muscles, which are thus stimulated to contraction; or to glands, which are stimulated to secretion. It is generally believed, as the result of many observations and experiments, that consciousness is not associated with the transmission of impulses along the nerves ; but that, when the molecular thrill reaches the brain, or some part of it, there, under appropriate conditions, consciousness emerges.
The group of structures consisting of (1) afferent nerve, with its sensory termination, (2) nerve-centre, and (3) efferent nerve, with its motor or other termination, is spoken of as the nervous are. It is called into activity by a stimulus applied to the sensory termination of the afferent nerve, and the motor or other result of its activity is spoken of as the response. The response is always more or less complex, involving the balanced and nicely regulated action of several, often many, muscles. And it is clear that the balanced action of several muscles must be due to the transmission to
(174) them of separate impulses duly graduated in intensity. The graduation of the outgoing impulses, as the result of thee receipt of incoming impulses, is effected in and by the nerve-centre, and is spoken of as co-ordination ; and this co-ordination may or may not be accompanied by conscious conti-ol. It is with the nature and the -relations of coordination a and control that we have to deal in this chapter. But we must deal with them in mere outline, and, so to speak, diagrammatically. The physiology of the question is difficult and full of technicalities ; and to a large extent it is external to, though closely bordering on, psychology. Unfortunately, too, the exact relations of physiological processes to the states of consciousness which we experience are still obscure and in large degree conjectural. I can only give the view which appears to me the most probable and that which is in best accord with known facts, not a tithe of which can be here adduced.
There can be little or no question that what one may term the groundwork of co-ordination is a matter of inherited organic structure in the nerve-centres. Hence, not infrequently, co-ordinated responses to stimuli are tolerably perfect at or very soon after birth. In all the higher mammals the exceedingly complex series of motor operations concerned in sucking and swallowing is at birth performed with sufficient exactitude to ensure the continuance of life. The little pig, or the baby hippopotamus, can very soon run about with surprising assurance. The human infant, though it is so much more helpless, clings to your fingers with tenacious and well-regulated grip, and will hang suspended for a couple of minutes. Even the sneeze with which it greets the world, its cries, and the seemingly aimless movements of its limbs involve co-ordination more or less perfect.
It is, however, especially in those young birds which, like the chick, undergo prolonged development within the egg,
(175) and are hatched in a fairly advanced state of organic development, that inherited co-ordination of response is shown in its most marked form. If a chick, hatched out in an incubator, be kept secluded from the world for twenty-four hours or so and then be placed under observation, it will " cheep," walk, and peck with fair but not complete accuracy at crumbs or bits of white of egg. If a fly with clipped wings be placed before it the chick will follow and peck at it, catching it perhaps at the sixth or seventh peck and swallowing it. If water be placed before the chick in a shallow tin-it will perhaps take no notice ; but if it be induced to peck at something in the water, it will lift its head in the peculiar way fowls have when they drink. The stimulus of water in the beak gives rise to a very special co-ordinated response involving a great number of muscles. Now in this and other such actions, the first time each is performed, the chick would seem to be a little automaton, no doubt a conscious automaton in so far as the performance of the activity in question is accompanied by consciousness, but none the less an automaton in the sense that it performs the action merely in virtue of its living organic structure, because it is a piece of beautifully delicate, going mechanism. The action is automatic as opposed to con trolled. For it does not seem possible for control to be exercised over an activity in the absence of any experience of 1 the nature of that activity. It may indeed be suggested that ancestral experience of the performance of such activities may be inherited by the chick. But I hold that the hypothesis of inherited experience is unsupported by evidence, and unnecessary, since the facts may be more simply explained on the view I am here advocating. What is inherited is organic structure fitting the organism for the automatic performance of complex activities, the co-ordination of which is moderately accurate from the first. The initial performance of the activity is, however, accompanied by consciousness;
(176) and here we have the primary basis in experience for the subsequent control of the activity in question.
For no one can watch the development of chicks or other young animals during the early days of their life, without obtaining abundant evidence of control. Chicks, for example, at first peck indiscriminately at almost everything that catches their eye, notably at their own excrement. But this is bitter or unpleasant to them. And you may watch the stages of gradual avoidance of pecking at this material, ranging from mere hesitation to complete neglect. Ladybirds are at first picked up, and then dropped with some comical wiping of the bill on the ground; very soon they are left quite untouched, and apparently unnoticed. _These, though simple cases, are examples of activities under control as the result of experience. And while nasty things are thus avoided, nice things are seized with increasing avidity and eagerness. Here, in fact, we have in simple expression that which is the essential feature of control, the inhibition of activities which are distasteful and associated with discomfort, and the conscious reinforcement of activities which are pleasurable and lead to satisfactory results.
The question now arises: Can we distinguish between nerve-centres whose function is the automatic co-ordination of activities, and other nerve-centres which are associated with the function of control? With a view to finding an answer to this question, let us run briefly over some of the chief features of the anatomical structure of the central nervous system. In the first place, there is the spinal cord, lying within and protected by the arches of the vertebral column Communicating with it there are it number of spinal nerves, each of which just before joining the cord divides I to two so-called roots, of which one, that nearer the mid-line of the back, contains the afferent fibres; while the other, or ventral root, is composed of efferent fibres. The cord itself consists of right and left halves, connected
(177) each with the other by narrow central bridges of nervous matter. The essential structures in each half are, --First, an internal nervous tangle of, delicate fibrils, some of which are connected with conspicuous nerve-cells, the tangle and the cells constituting the grey matter. This is to be regarded as a series of connected co-ordinating centres, but whether the conspicuous cells are mainly instrumental in co-ordination, or whether their function is chiefly that of maintaining in due order the nutrition of the nerve-fibres and fibrils, is an unsettled point. Secondly, external to the grey matter are longitudinal tracts of fibres running up and down the cord, one of which lying on the dorsal side may, for reasons which will shortly appear, be particularized. It is termed the pyramidal tract. This and other tracts constitute the so-called white matter of the cord. Thirdly, there are the bridges of nervous matter connecting the two halves of the spinal cord.
Traced upwards, the cord expands at the base of the skull to form the lowest part of the brain, termed the bulb or medulla oblongata. Here the internal grey matter, of increased size, and, external to it, the white matter, are still recognizable; the pyramidal tract is conspicuous, and to a large extent crosses over, right to left and left to right. Above the bulb, lying between it and the large cerebral hemispheres, is a complex series of nerve-centres with tracts of fibrous white matter, which it must suffice for us to group together as the "lower brain centres." Here and in the bulb are the centres in association with the optic nerve and with the cranial nerves coming from tongue, palate, ear, and the skin of the face; and going to the muscles of eye, tongue, and jaws, and to the larynx, lungs, heart, -and stomach. But these only form a small proportion of the grey matter of these centres. A far larger proportion is composed of a nervous tangle, concerned, as we shall presently see, with the co-ordination of activities, and receiving from all parts of the cord ascending or afferent impulses by
(178) a special tract, the so-called " median posterior tract." Right through these lower parts of the brain run strands of fibres continuous with those to which allusion has more than once been made as constituting the pyramidal tract.
The highest brain-centres are the cerebral hemispheres. These, as one of our greatest living physiologists has said, seem to stand apart from the rest of the brain. They are connected by tracts of fibres with the lower brain-centres, including the cerebellum ; while the cortex, consisting of grey matter formed of a nervous tangle with nerve cells, is directly connected with the before - mentioned pyramidal tract. This tract consists entirely of outgoing or motor fibres, and by its means the cerebral cortex is in direct connection with the centres associated with those cranial nerves which are motor in function, and with the centres of the spinal nerves throughout the whole length of the cord. These facts, then, have especially to be noticed with regard to the cerebral hemispheres;, first, that they stand to some extent apart from the rest of the central nervous system ; and, secondly, that though there seems to be no direct connection between the sensory nerves and the cerebral cortex (such connection being indirect through the intervention of lower brain-centres), there is, by means of the pyramidal tract, a direct connection between the cerebral cortex and the motor-centres of both cranial and spinal nerves. In view of these fact% the following hypothesis suggests itself: -that the. spinal cord and lower brain-centres afford the mechanism of co ordination ; that from this mechanism impulses pass upwards to the cerebral hemispheres which constitute the organic mechanism for control ; and that this control is brought to bear directly on the motor centres by means of the pyramidal tract. The diagrammatic representation of the nervous system given in Fig. II is drawn in accordance with this view. The cerebral hemispheres at the top of the figure are separated off from the rest of the
(179) nervous system, and the pyramidal tract is separated from he rest of the spinal cord. It should be noted that this tract is relatively most marked in man; it is less well developed in the monkey, still less in the dog, and is scarcely if at all recognizable in the lower vertebrates. It is probable, however, that in all cases there is some direct motor communication between the cerebral hemispheres, or mechanism of control, and the several motor-centres of the mechanism of co-ordination.
We must now briefly consider how far known facts of observation tend to bear out this hypothesis. In the frog, the cerebral hemispheres may be removed without killing the animal, which ay be kept alive for a prolonged period after the operation. Such a frog may perform all the necessary and usual bodily movements almost or quite as ell as an unmutilated animal. The removal of the cerebral hemispheres does not seem to have materially modified he mechanism of automatic co-ordination. The frog will eat when food is placed in its mouth, will even catch and a allow flies which co me into its neighbourhood. If laid on its back it will, after a few struggles, regain its natural position. If stimulated, it will' crawl, and leap, and avoid conspicuous obstacles. If thrown into water it will swim vigorously and for a long period, and ill crawl out on a piece of wood or on the sides of the pool. Placed on a board, it will sit up in the usual attitude but when the board is so tilted that the body is thrown out of equilibrium,
(180) the frog will crawl up so as to reach a secure position.. By constantly moving the board, the animal may be kept on the move for an indefinite period. If its flanks be gently stroked the frog will croak, answering to this stimulus with mechanical regularity. In all respects the frog appears to be a responsive automaton, with definite and accurate powers of co-ordination. But all voluntary control of action appears to have been removed. The animal seems quite incapable of profiting by experience. If left to itself, it will remain squatting' on the same spot until it dies.
In warm-blooded animals the effects of the removal of he cerebral hemispheres are more serious, and it is less easy to keep them alive. In birds, however, when they survive the. shock, a drowsy sleepy condition follows the operation. They assume a natural position, and only move therefrom on the application of a stimulus. This sleepiness may pass by, and' the bird may walk about restlessly and aimlessly, just as the frog swims when it is placed in water. A pigeon, so deprived of its cerebral hemispheres, will turn out of her course to avoid an obstacle ; but it makes no difference whether the obstacle is an inanimate body, a cat, a dog, a bird of prey', or another individual of the same species. She is sensitive to sounds as such, but it matters not whether the sound be the cooing of a mate, the rattling of peas, or the call-whistle which suggests feeding-time to its uninjured companions. The male pays no attention to the hen; the mother takes no notice of her young. On the whole, then, the observations, which have been made seem to justify the view that by the removal of the cerebral hemispheres the bird has been deprived, not of its power of co-ordination, but of its power of voluntary control. And the observations that have been made on mammals, during the short time that they survive the operation, do not tend to negative but rather to support the view that the loss of the cerebral hemispheres involves loss of voluntary control but not loss of adapted co-ordina
(181) -tion. Automatism remains, out of ability to profit by experience there is little or no evidence.
If we thus regard the cerebral hemispheres as constituting the organic mechanism of control,, and the pyramidal tract the channel by means of which control is brought to bear lower centres of co-ordination, we must also unquestionably regard the apparatus as delicately diffeientiated, and the differentiations as transmitted by inheritance. Much admirable physiological research has been of late years directed to the mapping out of the motor control centres in the cerebral hemispheres. These are often spoken of as motor centres, but the use of the phrase control centres ore accurately suggests their true function. It is noteworthy that the stimulation of the appropriate centres calls, to play not merely muscular contractions but co-ordinated motor activities. And there can be little question that each centre, either through different nerve-fibres or more probably rough the same fibres, has a two-fold function,-- that of enforcement of the activity, and that of inhibition or checking of the activity. How this inhibition is effected is a difficult physiological problem, which does not concern us ere. Nor do the details of the mapping of the centres in the cerebral cortex concern us. This is a matter of brain-physiology not of psychology. There is, however, one physiological, or rather anatomical, observation which, if it be confirmed, is of great interest from the psychological point of view. It is stated that in the brain of the newly-born infant, while the fibres running up from the lower brain-centres to the cerebral hemispheres and those running from the cortex to the pyramidal tract are already developed, the "association fibres "-that is to say the fibres funning in the cerebral hemispheres from ventre to centre -are not developed but are established in the individual after the brain ,has entered upon its duties and its functional activity. This anatomical observation accords with the psychological view
(182) that the association of ideas is a matter of individual establishment, and is not, at any rate in its details, a matter of inheritance.
On the hypothesis which is here adopted, the animal which is deprived of its cerebral hemispheres is a mere automaton ; and the question arises whether, under these abnormal conditions, it is a conscious automaton. The, answer to this question is, and is likely to remain, wholly' conjectural. I shall assume that it is an unconscious automaton, and adopt the hypothesis that consciousness is associated with the molecular disturbances which take place, in the cerebral hemispheres. My reason for taking this view is that, as it seems to me, the primary aim, object, and put-' pose of consciousness is control. Consciousness in a mere automaton is a useless and unnecessary epi-phenomenon. As will be seen in a later chapter, however, I am very far' from denying that some dim foreshadowing of that which we know as consciousness is an accompaniment of the functional activity of all nerve-centres. But I think that we may well regard this as lying in the infra-conscious region of our psychical curve, and therefore as extra-marginal to the field of our ordinary consciousness. I assume then that in us and in the higher animals (vertebrates) consciousness is associated with the - functional activity of the cerebral hemispheres.
Let us now go back to our little chick that pecks more or less automatically at some white unpleasant substance, but, finding it distasteful, checks after a few trials the motor activities involved in pecking and leaves the substance alone. And let us endeavour to represent in a diagram the manner in which such control may be brought to bear. It must be remembered that this is a diagram and nothing more, and if at first sight it looks somewhat complex we must remember that the probabilities are that it errs, among other things, in being almost absurdly too simple. In the diagram the
(183) cerebral hemispheres are as before represented, for purposes of illustration, as separated from the lower brain-centres which lie beneath, and the pyramidal tract is also separated off from the rest of the nervous system. It is so drawn to emphasize the hypothesis that the mechanism of control is distinct from the mechanism of autornatic co-ordination. The first stage of the process is the reception of a retinal stimulus. This gives rise to an afferent impulse by which the centres for the co-ordination of the activity of pecking are thrown into activity, as the result of which the efferent impulse.-, for that action leave the cord at the lower part of the diagram. This is the primary result of the stimulus. Put there is a secondary result. 'The impulse not only sets in motion the co-ordinating apparatus, but (probably through the fibres known as the "optic radiation ") throws into activity the visual centres V
(184) in the cerebral hemispheres. So much for the results of the retinal stimulus. The action of pecking now takes place. But this activity stimulates a number of afferent fibres, giving rise to what is termed -in the diagram a pecking stimulus, and the impulses thus started probably again have two results. In the first place, they may- have a direct influence on the, centres for automatic co-ordination; and secondly, they throw into activity the cerebral centres M, which are associated with motor consciousness, or the consciousness of the action of pecking which is taking place. Now there probably already exist in the hemispheres inherited and well-established connections between the centres of motor consciousness and the control centres of that particular activity. Hence the control centre is thrown into activity, and through the pyramidal tract either enforces or inhibits the continuance of the activity. We have now three centres in the cerebral hemispheres thrown into activity in rapid succession, the visual centres V, the centres of motor consciousness M, and the control centre. And here we must call to our aid the fact, which psychologically is unquestionable, of association. The states of consciousness concomitant with the activities of V, of M, and of the control centres, if such there be, thereafter tend to be suggested in the order of their primary occurrence. And this we must represent on our diagram by connecting lines between V, M, and the control centre.
But in the case under consideration, the action of pecking causes the chick to seize something that has an unpleasant and bitter taste, so that we have following rapidly upon the retinal stimulus and the pecking stimulus a taste stimulus. This again probably gives rise to impulses which first take effect, directly upon the mechanism of automatic co-ordination, but which also throw into activity the sensory centre s for taste T in the cerebral hemispheres. The sequence is so rapid that probably all- four centres in the hemispheres,
(185) the visual centres, the taste centres, the centres of motor consciousness, and the control centre, are all in a state of molecular disturbance at the same time, and thus all become associated each with the other. But the consciousness which is concomitant with the activity of T is unpleasant and distasteful, and the effect of T upon the control centre will therefore be inhibitive. And even supposing that the effects of V and of M upon the control centre are slightly augmentative, and tend in some degree to enforce the activity, still the strongly inhibitive effect of T will prevail and the activity will be checked.
Such, in brief, is the way in which, in a very simple case, control may perhaps be brought to bear upon the mechanism for automatic co-ordination. All such schemes must, however, be regarded as the merest diagrams, and of little save as showing the kind of way in which control is anatomically or physiologically possible. There must, of course, be nothing in them which contradicts known facts, anatomical, physiological, or psychological. And this, I venture to hope, is the case with the scheme here given.
It is well to restrict the term reflex action to that which is performed through the instrumentality of the mechanism for automatic co-ordination, and of this alone. Thus the first peck resulting from a retinal stimulus is a primary reflex action. I am aware that some eminent physiological psychologists are wont to urge that all cerebral activity " partakes of the nature of" or "may be reduced to the type of" reflex action. And if anything which involves a nervous circuit be termed reflex action, this is logical enough. But on the view I am here advocating it is well to restrict the term reflex action to that which is a matter of animal automatism, and thus to mark and emphasize the distinction between this and the higher process of control. It is probable, however, that control serves to modify and impress new characters on the automatic responses of the co-ordinating
(186) mechanism. Control involves, and probably always involves, a double circuit, -- the lower reflex circuit and the higher control circuit. When during the life, and especially the early life, of the individual, the lower reflex circuit is constantly aided and enforced, or at any rate uniformly permitted, by the control circuit, it will become thereby the more firmly established; where it is inhibited, it will tend by disuse to disappear as a reflex; and where it is modified, certain elements of the activity being reinforced and others checked, it will tend to persist in this modified form. Control may then be withdrawn, and the co-ordinating apparatus left to carry on the activity in its modified form. Thus are habits formed, and a whole class of activities known as secondary reflex actions are established. Such habits will carry with them the purposive nature impressed upon them by the control under which they have taken form. Suppose, then, a pigeon, in which such habits have been established, be the subject of the operation of the removal of the cerebral hemispheres, the results of their educating influence on the automatic mechanism will remain though they are themselves removed. Hence the individuality of habit might still remain to some degree in the mutilated bird ; and such residue of habit, individually acquired, would not in any way invalidate the view that the cerebral hemispheres are the sole control-centres, and the sole organ of consciousness. What would invalidate this view is evidence going to show that the hemisphereless animal is able to profit by experience and can be educated. If we eliminate the improvement of condition in the patient, due to the gradual recovery from the shock of the operation, such evidence does not appear to be at present forthcoming.
We may now turn to some of the more essentially psychological aspects of the scheme that has above been presented. The state of consciousness that accompany the activity- of the centres V, M, and T have a. two-fold aspect. In the
(187) first place, they are symbolic of occurrences in the environment which affect the organism through the afferent nerves. From this aspect we have already considered them, in what has been said concerning impressions. In the second place, they carry with them what is figuratively spoken of as a "tone" of pleasurable or painful feeling. Primitively, and in the lower organisms, control is determined by the predominance of pleasurable or painful tone in the sensory centres which are at any time conspiring to influence the centres of control. For man, in so far as he is a reflective being who frames ideals of conduct, this statement is too crude, and is contradicted by experience, unless we extend the meaning of the words " pleasurable " and " painful in a way that can scarcely be regarded as satisfactory. This matter, however, we must also defer for future consideration. Here it will be sufficient to generalise the statement above made, and to say that the nature of control is determined by the predominant emotional tone in the sensory centres which are conspiring to influence the centre of control.
Now, is there any other kind or aspect of consciousness besides these two -- (1.) that which is symbolic of occurrences which affect the afferent nerves, and (2.) that which maybe described as the accompanying emotional tone? Do we, in enumerating all the elements of consciousness which fall under these two categories, exhaust to the full the contents of the curve of consciousness ? Different schools of psychologists give very different answers to these questions. According to one school, in addition to the sensory elements and those of feeling, there is a third-and quite distinct kind or aspect of consciousness, to which the name volition is given. According to the other school, there are no primary volitional elements. The phenomena attributed to volition may, they contend, be readily resolved into sensory elements accompanied by tone of feeling. It has, for example, been recently advanced, that what we term volition is sufficiently
(188) described as a mental picturing of an activity to be per.. formed, followed by the actual experience of the carrying-out of the activity so pictured. To this a disciple of the volitional school would reply, that though the description is fairly accurate so far as it goes, it nevertheless quietly ignores, without disproving, the volitional element. He would probably indicate its inadequacy in the case of the volitional non-performance of a suggested activity; and would contend -that, in any case, he finds in his own experience something quite different from sensory elements or elements of feeling, namely, a consciousness of control according as the activity in question is enforced or suppressed. Without presuming to decide between these schools, I may point out the fact that, if there be primary volitional elements, if, that is to say, the will be a matter of direct experience and not a complex product of reflection, this may, in accordance with our, scheme, be due to the fact that there is a distinct type of consciousness accompanying the functional activity of the control centres themselves.
Merely throwing this out as a suggestion, and without offering at present any opinion as to the -probabilities one way or the other, let us now proceed to correlate a little more clearly and definitely the physiology and the psychology of control. Physiologically, the activity of the control centre is at any moment determined by the impulses reaching it from the several centres in the cerebral hemispheres which have been thrown into a state of molecular disturbance by a stimulus. Psychologically, these molecular disturbances are, or are accompanied by, those sensory and emotional elements which contribute to form states of consciousness. Now let us suppose that consciousness is fully occupied with the nice control of some important bodily activity. Then, since the total content of consciousness in any given moment constitutes the empirical me of that moment, it is clear that this empirical .1 controls the activity
(189) in question. In automatic acts, in so far as they are accompanied by consciousness, such consciousness is a mere spectator, but in controlled activities consciousness is more than a spectator-it takes the helm and guides. And consciousness is free to guide in accordance with the laws of its inherent nature, save in so far as it is thwarted by some external constraint. In the free-will controversy, which we cannot enter into here, much confusion often arises from a failure to distinguish between the real freedom of the individual to control his activities in accordance with the laws of his inherent nature, and a supposed freedom to transcend, these laws. But what we have to notice here is that, as a matter of psychology , motor control over the bodily activities is a function of, and is determined by, that complex state of consciousness which we call the empirical me.
There is another aspect of control-and one of great importance in psychology-which we must now briefly consider. We may fitly introduce it by asking the question: How far can control be exercised over the attention? We may describe attention as the bringing of something to the focus of consciousness, and the holding it there. In the chapter on Suggestion and Association, we considered at sufficient length the manner in which impressions and ideas are brought to the focus. Now, with regard to impressions, of which we may take visual impressions as the type, there is a large amount of motor adjustment necessary in order to make and to hold an object focal: and this is undoubtedly under definite and accurate control in the sense in which we have throughout been using this word. Suppose we thus make focal a distant church spire in the midst of a visual scene. Although the. details of the adjustment are carried out by the lower centres, the fixing of the eyes on just that particular object, and making it focal, is a matter of conscious cerebral control, But now, suppose that subsequently under other circumstances, sitting perhaps in our armchair,
(190) an image or idea of the church spire is brought to the focus through association. How far are we able to hold it there, and in what way is -control exercised in this case? I suppose it is a matter of universal experience, that we can not retain it in the focus as idea, with anything like the same ease with which we could retain it as impression. We may, for our present purpose, neglect such facts as that not improbably, while the idea is in the focus, the control centre which was concerned in focussing it as an impression is thrown into sub-dominant activity; and that the appropriate motor adjustments may in some cases be actually made, the eyes being focussed as if for the reception of the impression, and thus appearing to an onlooker to be fixed on vacancy. These subsidiary matters we may neglect, that we may emphasize the essential question:-Can the cerebral hemispheres which exercise control over the lower automatic centres exercise control also over their own activity? In other words, Can they exercise control over their own sensory centres, and thus modify or guide the flow of ideas ?
Before attempting to answer these questions; let us clearly remember the sense in which we have employed the term " control." It is motor control, control over the mechanism of automatic activity, that we have been dealing with throughout. And we have just seen that in attention, as directed towards impressions, there is this control over the motor apparatus concerned in focussing. But when we ask whether we can exercise control over the flow of our ideas, it is clear that we are no longer speaking of direct motor control. The, only possible way in which we can have motor control over ideas, is through the regulation of the vascular supply of the sensory centres in the cerebral hemispheres. It is just possible that this may take place. It is well known that the supply of blood to the various organs and parts of organs is regulated to a nicety, for the most part through the intervention of the automatic mechanism,
(191) It is also well known that the functional activity of any part is enhanced, within normal and natural limits, by increased blood supply. And though as a rule, in most people, the regulation of the calibre of the blood capillaries is not in the least degree subject to conscious control, it is at least degree physiologically conceivable that there are in the cerebral cortex control centres for the vascular supply of the sensory centres within the hemispheres, and that through them the activity of the centres may be increased, and the ideas therein rendered more vivid and lasting. There is at present no definite evidence that this is the case.
Is there, then, any control of the cerebral hemispheres over the activity of their own sensory centres ? We shall do well, perhaps, to regard the matter from the psychical side, and in doing so we must bear in mind how states of consciousness are determined. Let us represent the states of consciousness in three successive moments, thus : --
Then, supposing that A b c &c. represents the total psychical content of the wave of consciousness in the first moment, this represents also the we of empirical psychology in that moment. But A b c &c. of moment i determines (subject to the qualifications given in a previous chapter, p.82) C b d &c. of moment 2, which constitutes the empirical vie of that moment. Similarly C b d &c, of moment 2 determines D c M &c. of moment 3; and so on throughout any given series of moments of consciousness. In other words, it is the empirical I which constantly determines the sequence of ideas. That same psychical I, which takes effect through the control centres on the motor
(192) activities of the body, takes effect also through association fibres on the sensory centres which are concerned in the production of ideas.
The question, however, still remains, whether there is any power of augmentation or of inhibition of the activity of sensory centres. That is to say, supposing any given idea or image is dominant, is there any mechanism for either augmenting or damping-down the activity of the centre with the molecular disturbance of which the idea is associated? We cannot at present answer this question from the physiological point of view; and psychologically the evidence is not conclusive, one way or the other. The most we can say physiologically is, that there is no a priori reason why such inhibition, and its correlative augmentation, should be impossible. It is unquestionable that the inhibition of motor activities is the result of the action of the control centres, not directly on the muscular mechanism, but indirectly on the lower centres for the automatic coordination of motor activities. The augmentation or inhibition is exercised by nerve-centres on nerve-centres, and there is therefore no a priori reason for rejecting the hypothesis, that the activity of sensory centres can be augmented or inhibited by special control centres, developed for that special purpose. More than this in the present state of brain-physiology we cannot say.
And, psychologically, the evidence is not conclusive. We have to distinguish between relative increase or diminution of conscious intensity through the direction or diversion of attention, and the absolute increase or diminution thereof through augmentation or inhibition. And this is by no means easy. It should he clearly noted, however, that inn the absence of such control over the sensory centres as we are now considering, the direction or diversion of attention is wholly dependent on motor control over the parts by the instrumentality of which' impressions are received. There
(193) can be no control over the sequence of ideas. Whether, as a matter of observation, there is any such control over the centres which are concerned in the production of sense impressions, it is difficult to decide. Some time ago I chanced to have to wait for half-an-hour or so between two bands about equidistant from me. I amused myself by making some experiments on my power of attention, and very shortly found that I could either attend to one band or the other to the practically complete neglect of its rival, or could combine the two in an excruciating jumble of discords. With my attention well fixed on either of them, I experienced little or no discomfort from the sounds produced by the other; but when I allowed both to occupy my attention, the effect was most disquieting. I may say that in such an experiment the difficulty is, when the combined clash is in focus, to select the strains of one of the two bands ; when once this is effected, the holding of those strains in focus is comparatively easy. I suppose most people who have a fair musical ear can, during the singing of a chorale, select any one of the four parts and make that focal, the other parts being accompaniment to the selected part. How is this selection effected ? It is difficult to see bow any motor control over the parts concerned in audition could effect a differentiation between the soprano or the bass of a chorale as dominant in consciousness.
It need scarcely be said that there is a common and widespread belief that attention involves something more than motor control over the parts concerned in the reception of stimuli. Such a belief, founded as it is on wide if not always very discriminating self-observation cannot be wholly neglected. There are, moreover, not a few who believe that they can to some extent control their feelings, and their Sensitiveness to pain, physical and other, and that such control is susceptible of improvement by practice. In either of these cases- it is difficult to see how control can be exer-
(194) -cised, unless there is some cerebral provision for augmentation and inhibition through control centres.
Among the commonest phenomena of the hypnotic state are suggested hyperaesthesia, on the one hand, and anaesthesia on the other. In - some cases the senses become, through suggestion, extraordinarily acute ; in others, they seem to be abnormally dulled and blunted. In suggested hallucinations, under hypnosis, certain centres seem to be rendered extraordinarily susceptible to what we termed internal suggestion, so that the suggested images assume the vividness and insistency of impressions. It may be that these phenomena of the hypnotic state are partly caused by some at' present unexplained influence on control centres, which may have for their function the augmentation or inhibition of the activity of those cerebral centres which are concerned in sense-experience.
It is now time to sum up the conclusions we have reached,, and the suggestions we have made, with regard to automatism and control. The distinction I have drawn betweenautomatic activities and controlled action is a sharp one. On the scheme I have put forward, automatic activities involve afferent impulses, co-ordinating centres, and efferent impulses. In the performance of these activities the organism is an automaton, and the whole matter so far is purely. biological. Control of the motor activities involves, and must always involve, a loop-line, in the course of which there are developed certain centres, called control-centres, whose function it is either to augment or to inhibit the lower co-ordinating centres of the automatic mechanism. Asso- ciated with these control centres of the loop-line there are sensory centres, the functional activity of which is conscious or is associated with consciousness. These sensory centres are so disposed on the loop-line as to determine the nature of the activity, augmenting or inhibitory, of the control centres according to the emotional tone associated with the
(195) functioning of the sensory centres. The sensory centres and the control centres are, in the higher vertebrates, situate in the cerebral hemispheres of the brain. So far the control is entirely motor; and so far there is much in the anatomy and physiology of the brain and central nervous system in support of the hypothesis here put forward. It is further suggested as a possibility -- at present unsupported by, but so far as I know not negatived by, cerebral anatomy and physiology-that there may be cerebral centres for the control of the activity of the sensory centres. This hypothesis is put forward on purely psychological grounds. It is contended that if there is any, control of cerebral activity and its mental concomitants, -if there is any faculty of attention other than that involved in the admitted motor control over the parts concerned in the reception of sensestimuli, this must be effected by means of a loop-line, with its associated control centres. For control is due to augmenting or inhibitory impulses, and such impulses must come from outside the system so controlled. This last proposition may seem to stand in need of proof and elucidation, but I confess that it seems to me to be self-evident. For suppose a sensory centre be thrown into a state of activity, and that its functioning is associated with some form or mode of consciousness, I fail to see in what way it could be self-augmenting or self-inhibitory. We may assume that the activity is either painful or pleasurable. One can understand how its pleasurable or painful tone may differently affect a centre lying outside it with which it may communicate. But I am unable to understand how its pleasurable or painful tone could either increase or damp-down its own activity. 'Such a supposition appears to involve the illegitimate assumption, as I deem it, that the pleasure or the pain is something external to the activity, and can exercise control over it, Hence,- for a psychology that endeavours to work hand-in-hand with physiology the control of any functioning centre
(196) must be due to impulses, augmenting or inhibitory, coming 'to that centre from some other centre external to it.
Nothing has been said in this chapter concerning automatism or control in the higher invertebrates, such as the bee or the ant. Their actions seem to warrant the belief that in them, too, there is-besides the mechanism for automatic co-ordination -- a mechanism of control. But at present nothing is known of definite control centres in these organisms, supposing such centres to exist. There is here a fruitful field for investigation, if we could only find a satisfactory point of departure.
In conclusion, it should be noted that control, whether it be motor-control. or the suggested intra-cerebral control of the attention, should be psychologically distinguished from the sense of effort by which it is sometimes accompanied. Such a sense of effort is almost unquestionably a sensory product of the motor activities. The knit brow, slightly clenched teeth, somewhat strained respiration, and other motor concomitants, not only of motor-control but also of close and difficult thought and attention, are not without their psychical effects. And these we name effort. The part which motor impressions play in psychology, though often neglected, is of the utmost importance, as we have already seen in our discussion of Synthesis and Correlation.
Note. -- The development of what is known as the "neurone theory " involves a restatement of the nature of the physiological processes of the brain. The reader will do well to consult Sir Michael Foster's Wilde Lecture " On the Physical Basis of Psychical Events" (Manchester Memoirs, vol. xlii., 1898, No. 12), and Mr. McDougall's paper "On the Seat of the Psycho-physical Processes," in which there are ample references to the literature of the subject. Mr McDougall's contribution was published, during the winter of 1901, in Brain (part xcvi., p. 577).[1903.]