THE CORTEX
=Cortex the Seat of Consciousness.=--Experiments in connection with the different nerve cords and centres have demonstrated that intelligent consciousness depends upon the nerve centres situated in the cortex of the cerebrum. For instance, a sensory impulse may be carried inward to the cells of the spinal cord and upward to the cerebellum without any resulting consciousness. When, however, the stimulus reaches a higher centre in the cortex of the brain, the mind becomes conscious, or interprets the impression, and any resulting action will be controlled by consciousness, through impulses given to the motor nerves. It is for this reason that the cortex is called the seat of consciousness, and that mind is said to reside in the brain.
=Localization of Function.=--In addition, however, to placing the seat of consciousness in the cortex of the brain, psychologists also claim that different parts of the cortex are involved in different types of conscious activity. Sensations of sight, for instance, involve certain centres in the cortex, sensations of sound other centres, the movements of the organs of speech still other centres. Some go so far as to claim that each one of the higher intellectual processes, as memory, imagination, judgment, reasoning, love, anger, etc., involves neural activity in its own special section of the cortex. There seems no good evidence, however, to support this view. The fact seems rather that in all these higher processes, quite numerous centres of the cortex may be involved. The following figure indicates the main conclusions of the psychologists in reference to the localization of certain important functions in distinct areas of the cortex.
[Ill.u.s.tration: REFLEX ACTS]
=Nature of Reflex Action.=--While a lower nerve centre is not a seat for purposeful consciousness, these centres may, in addition to serving as transmission points for cortical messages, perform a special function by immediately receiving sensory impressions and transmitting motor impulses. A person, for instance, whose mind is occupied with a problem, may move a limb to relieve a cramp, wink the eye, etc., without any conscious control of the action. In such a case the sensory impression was reported to a lower sensory centre, directly carried to a lower motor centre, and the motor impulse given to perform the movement. In the same way, after one has acquired the habit of walking, although it usually requires conscious effort to initiate the movements, yet the person may continue walking in an almost unconscious manner, his mind being fully occupied with other matters. Here, also, the complex actions involved in walking are controlled and regulated by lower centres situated in the cerebellum. In like manner a person will unconsciously close the eyelid under the stimulus of strong light. Here the impression caused by the light stimulus, upon reaching the medulla along an afferent nerve, is deflected to a motor nerve and, without any conscious control of the movements, the muscles of the eyelid receive the necessary impulse to close. Actions which are thus directed from a lower centre without conscious control, are usually spoken of as reflex acts.
Acts directed by consciousness are, on the other hand, known as voluntary acts. The difference in the working of the nervous mechanism in consciously controlled and in reflex action may be ill.u.s.trated by means of the accompanying figures.
[Ill.u.s.tration: FIG 1]
[Ill.u.s.tration: FIG 2]
The heavy lines in Figure 1 on the opposite page show that the sensory-motor arc is made through the cortex, and that the mind is, therefore, conscious both of the sense stimulus and also of the resulting action. Figure 2 shows the same arc through a lower centre, in which case the mind is not directly attending to the impression or the resulting action.
=Function of Consciousness.=--The facts set forth above serve further to ill.u.s.trate the purposeful character of consciousness as man interprets and adjusts himself to his surroundings. So long, for instance, as the individual walks onward without disturbance, his mind is free to dwell upon other matters, cortical activity not being necessary to control the process of walking. If, however, he steps upon anything which perhaps threatens him with a fall, the rhythmic interplay between sensory and motor activity going on in the lower centres is at once disturbed, and a message is flashed along the sensory nerve to the higher, or cortical, centres. This at once arouses consciousness, and the disturbing factor becomes an object of attention. Consciousness thus appears as a means of adaptation to the new and varying conditions with which the organism is confronted.
CHARACTERISTICS OF NERVOUS MATTER
=A. Plasticity.=--One striking characteristic of nervous matter is its plasticity. The nature of the connections within the nervous system have already been referred to. Mention has also been made of the fact that numerous connections are established within the nervous system as a result of movements taking place within the organism during life. In other words, the movements within the nervous system which accompany stimulations and responses bring about changes in the structure of the organism. The cause for these changes seems to be that the neurons which chance to work together during any experience form connections with one another by means of their outgrowing fibres. By this means, traces of past experiences are in a sense stored up within the organism, and it is for this reason that our experiences are said to be recorded within the nervous system.
=B. Retentiveness.=--A second characteristic of nervous matter is its retentive power. In other words, the modifications which accompany any experience, besides taking on the permanent character referred to above, pre-dispose the system to transmit impulses again through the same centres. Moreover, with each repet.i.tion of the nervous activity, there develops a still greater tendency for the movements to re-establish themselves. This power possessed by nervous tissue to establish certain modes of action carries with it also an increase in the ease and accuracy with which the movements are performed. For example, the impressions and impulses involved in the first attempts of the child to control the clasping of an object, are performed with effort and in an ineffective manner. The cause for this seems to be largely the absence of proper connections between the centres involved, as referred to above. This absence causes a certain resistance within the system to the nervous movements. When, however, the various centres involved in the movements establish the proper connections with one another, the act will be performed in a much more effective and easy manner. From this it is evident that the nervous system, as the result of former experiences, always retains a certain potential, or power, to repeat the act with greater ease, and thus improve conduct, or behaviour. This property of nervous matter will hereafter be referred to as its power of retention.
=C. Energy.=--Another quality of nervous matter is its energy. By this is meant that the cells are endowed with a certain potential, or power, which enables them to transmit impressions and impulses and overcome any resistance offered. Different explanations are given as to the nature of this energy, or force, with which nervous matter is endowed, but any study of these theories is unnecessary here.
=D. Resistance.=--A fourth characteristic to be noted regarding nervous matter is that a nervous impulse, or current, as it is transmitted through the system, encounters _resistance_, or consumes an amount of nervous energy. Moreover, when the nervous current, whether sensory or motor, involves the establishment of new connections between cells, as when one first learns combinations of numbers or the movements involved in forming a new letter, a relatively greater amount of resistance is met or, in other words, a greater amount of nervous energy is expended.
On the other hand, when an impulse has been transmitted a number of times through a given arc, the resistance is greatly lessened, or less energy is expended; as indicated by the ease with which an habitual act is performed.
=Education and Nervous Energy.=--It is evident from the foregoing, that the forming of new ideas or of new modes of action tends to use up a large share of nervous energy. For this reason, the learning of new and difficult things should not be undertaken when the body is in a tired or exhausted condition; for the resistance which must be overcome, and the changes which must take place in the nervous tissue during the learning process, are not likely to be effectively accomplished under such conditions. Moreover, the energy thus lost must be restored through the blood, and therefore demands proper food, rest, and sleep on the part of the individual. It should be noted further that nervous tissue is more plastic during the early years of life. This renders it imperative, therefore, that knowledge and skill should be gained, as far as possible, during the plastic years. The person who wishes to become a great violinist must acquire skill to finger and handle the bow early in life. The person who desires to become a great linguist, if he allows his early years to pa.s.s without acquiring the necessary skill, cannot expect in middle life to train his vocal organs to articulate a number of different languages.
=Cortical Habit.=--In the light of what has been seen regarding the character and function of the nervous system, it will now be possible to understand more fully two important forms of adjustment already referred to. When nervous movements are transmitted to the cortex of the brain, they not only awaken consciousness, or make the individual aware of something, but the present impression also leaves certain permanent effects in the nervous tissue of the cortex itself. Since, however, cortical activity implies consciousness, the retention of such a tendency within the cortical centres will imply, not an habitual act in the ordinary sense, but a tendency on the part of a conscious experience to repeat itself. This at once implies an ability to retain and recall past experiences, or endows the individual with power of memory.
Cortical habit, therefore, or the establishment of permanent connections within the cortical centres, with their accompanying dynamic tendency to repeat themselves, will furnish the physiological conditions for a revival of former experience in memory, or will enable the individual to turn the past to the service of the present.
=Physical Habits.=--The basis for the formation of physical habits appears also in this retentive power of nervous tissue. When the young boy, for instance, first mounts his new bicycle, he is unable, except with the most attentive effort and in a most laboured and awkward manner, either to keep his feet on the pedals, or make the handle-bars respond to the balancing of the wheel. In a short time, however, all these movements take place in an effective and graceful manner without any apparent attention being given to them. This efficiency is conditioned by the fact that all these movements have become habitual, or take place largely as reflex acts.
In school also, when the child learns to perform such an act as making the figure 2, the same changes take place. Here an impression must first proceed from the given copy to a sensory centre in the cortex. As yet, however, there is no vital connection established between the sensory centres and the motor centres which must direct the muscles in making the movement. As the movement is attempted, however, faint connections are set up between different centres. With each repet.i.tion the connection is made stronger, and the formation of the figure rendered less difficult. So long, however, as the connection is established within the cortex, the movement will not take place except under conscious direction. Ultimately, however, similar connections between sensory and motor neurons may be established in lower centres, whereupon the action will be performed as a reflex act, or without the intervention of a directing act of consciousness. This evidently takes place when a student, in working a problem, can form the figures, while his consciousness is fully occupied with the thought phases of the problem. Thus the neural condition of physical habit is the establishment of easy pa.s.sages between sensory and motor nerves in centres lower than the cortex.
CHAPTER XXI
INSTINCT
=Definition of Instinct.=--In a foregoing section, it was seen that our bodily movements divide into different cla.s.ses according to their source, or origin. Among them were noted certain inherited spontaneous, but useful, complex movements which follow, in a more or less uniform way, definite types of stimuli presented to the organism. Such an inherited tendency on the part of an organism to react in an effective manner, but without any definite purpose in view, whenever a particular stimulus presents itself, is known as instinct, and the resulting action is described as an instinctive act. As an example of purely instinctive action may be taken the maternal instinct of insects whose larvae require live prey when they are born. To provide this the mother administers sufficient poison to a spider or a caterpillar to stupefy it, and then bears it to her nest. Placing the victim close to her eggs, she incloses the two together, thus providing food for her future offspring. This complex series of acts, so essential to the continuance of the species, and seemingly so full of purpose, is nevertheless conducted throughout without reference to past experience, and without any future end in view. Instinct may, therefore, be defined as the ability of an organism to react upon a particular situation so as to gain a desirable end, yet without any purpose in view or any previous training.
=Characteristics of Instinct.=--An instinctive act, it may be noted, is distinguished by certain well marked characteristics:
1. The action is not brought about by experience or guided by intelligence, but is a direct reaction on the part of the organism to definite stimulation.
2. Although not the result of reason, instinctive action is purposeful to the extent that it shows a predisposition on the part of the organism to react in an effective manner to a particular situation.
3. An instinctive movement is a response in which the whole organism is concerned. It is the discomfort of the whole organism, for instance, that causes the bird to migrate or the child to seek food. In this respect it differs from a mere reflex action such as the winking of the eye, breathing, coughing, etc., which involves only some particular part of the organism.
4. Although not a consciously purposed action, instinct nevertheless involves consciousness. In sucking, for instance, sensation accompanies both the discomfort of the organism giving rise to the movements and also the instinctive act itself. In this respect it differs from such automatic actions as breathing, the circulation of the blood, and the beating of the heart.
=Origin of Instinct.=--The various instinctive movements with which an organism is endowed, not being a result of experience or education, a question at once arises as to their source, or origin. Instinct has its origin in the fact that certain movements which have proved beneficial in the ancestral experience of the race have become established as permanent modes of reaction, and are transmitted to each succeeding generation. The explanation of this transmission of tendencies is, that beneficial movements are retained as permanent modifications of the nervous system of the animal, and are transmitted to the offspring as a _reactive tendency_ toward definite stimuli. The partridge family, for instance, has preserved its offspring from the attacks of foxes, dogs, and other enemies only by the male taking flight and dragging itself along the ground, thus attracting the enemy away from the direction of the nest. The complex movements involved in such an act, becoming established as permanent motor connections within the system, are transmitted to the offspring as predispositions. Instinct would thus seem a physiological habit, or hereditary tendency, within the nervous system to react in a fixed manner under certain conditions. In many respects, however, instincts seem to depend more largely upon bodily development than upon nervous structure. While the babe will at first instinctively suck; yet as soon as teeth appear, the sucking at once gives way to the biting instinct. The sucking instinct then disappears so completely that only a process of education will re-establish it later. Birds also show no instinctive tendency to fly until their wings are developed, while the young of even the fiercest animals will flee from danger, until such time as their bodily organism is properly developed for attack. From this it would seem that instinctive action depends even more upon general bodily structure and development than upon fixed co-ordinations within the nervous system.
HUMAN INSTINCTS
On account of the apparently intelligent character of human actions, it is often stated that man is a creature largely devoid of instincts. The fact is, however, that he is endowed with a large number of impulsive or instinctive tendencies to act in definite ways, when in particular situations. Man has a tendency, under the proper conditions, to be fearful, bashful, angry, curious, sympathetic, grasping, etc. It is only, moreover, because experience finally gives man ideas of these instinctive movements, that they may in time be controlled by reason, and developed into orderly habits.
=Cla.s.sification of Human Instincts.=--Various attempts have been made to cla.s.sify human instincts. For educational purposes, perhaps the most satisfactory method is that which cla.s.sifies them according to their relation to the direct welfare of the individual organism. Being inherited tendencies on the part of the organism to react in definite ways to definite stimuli, all instinctive acts should naturally tend to promote the good of the particular individual. Different instincts will be found to differ, however, in the degree in which they involve the immediate good of the individual organism. On this basis the various human instincts may be divided into the following cla.s.ses:
1. _Individualistic Instincts._--Some instincts gain their significance because they tend solely to meet the needs of the individual. Examples of these would be the instincts involved in securing food, as biting, chewing, carrying objects to the mouth; such instinctive expressions as crying, smiling, and uttering articulate sounds; rhythmical bodily movements; bodily expression of fear, etc.
2. _Racial Instincts._--These include such instinctive acts as make for the preservation of the species, as the s.e.xual and parental instincts, jealousy, etc. The constructive instinct in man, also, may be considered parallel to the nesting instinct in birds and animals.
3. _Social Instincts._--Among these are placed such instinctive tendencies as bashfulness, sympathy, the gregarious instinct, or love of companionship, anger, self-a.s.sertion, combativeness, etc.
4. _Instincts of Adjustment._--Included among man"s native tendencies are a number of complex responses which manifest themselves in his efforts to adjust himself to his surroundings. These may be called instinctive so far as concerns their mere impulsive tendency, which is no doubt inherited. In the operation of these so-called instincts, however, there is not seen that definite mode of response to a particular stimulus which is found in a pure instinct. Since, however, these are important human tendencies, and since they deal specifically with the child"s att.i.tude in adapting himself to his environment, they rank from an educational standpoint among the most important of human instincts. These include such tendencies as curiosity, imitation, play, constructiveness and acquisitiveness.
=Human Instincts Modified by Experience.=--Although instinctive acts are performed without forethought or conscious purpose, yet in man they may be modified by experience. This is true to a degree even in the case of the instincts of the lower animals. Young spiders, for instance, construct their webs in a manner inferior to that of their elders. In the case of birds, also, the first nest is usually inferior in structure to those of later date. In certain cases, indeed, if accounts are to be accepted, animals are able to vary considerably their instinctive movements according to the particular conditions. It is reported that a swallow had selected a place for her nest between two walls, the surfaces of which were so smooth that she could find no foundation for her nest. Thereupon she fixed a bit of clay to each wall, laid a piece of light wood upon the clay supports, and with the stick as a foundation proceeded to construct her nest. On the whole, however, there seems little variation in animal instincts. The fish will come a second time to take food off the hook, the moth will fly again into the flame, and the spider will again and again build his web over the opening, only to have it again and again torn away. But whatever may be the amount of variation within the instincts of the lower animals, in the case of man instinctive action is so modified by experience that his instincts soon develop into personal habits. The reason for this is quite evident. As previously pointed out, an instinctive act, though not originally purposeful, is in man accompanied with a consciousness of both the bodily discomfort and the resulting movements. Although, therefore, the child instinctively sucks, grasps at objects, or is convulsed with fear, these acts cannot take place without his gradually understanding their significance as states of experience. In this way he soon learns that the indiscriminate performance of an instinctive act may give quite different results, some being much more valuable to the individual than others. The young child, for instance, may instinctively bite whatever enters his mouth, but the older child has learned that this is not always desirable, and therefore exercises a voluntary control over the movement.
=Instincts Differ in Value.=--The fact that man"s instinctive tendencies thus come within the range of experience, not only renders them amenable to reason, but also leaves the question of their ultimate outcome extremely indefinite. For this reason many instincts may appear in man in forms that seem undesirable. The instinct to seek food is a natural one, yet will be condemned when it causes the child to take fruit from the neighbour"s garden. In like manner, the instinct to know his surroundings is natural to man, but will be condemned when it causes him to place his ear to the keyhole. The tendency to imitate is not in itself evil, yet the child must learn to weigh the value of what he imitates. One important reason, therefore, why the teacher should understand the native tendencies of the child is that he may direct their development into moral habits and suppress any tendencies which are socially undesirable.
=Education of Instincts.=--In dealing with the moral aspects of the child"s instinctive tendencies, the educator must bear in mind that one tendency may come in conflict with another. The individualistic instinct of feeding or ownership may conflict with the social instinct of companionship; the instinct of egoism, with that of imitation; and the instinct of fear, with that of curiosity. To establish satisfactory moral habits on the basis of instinct, therefore, it is often possible to proceed by a method of subst.i.tution. The child who shows a tendency to destroy school furniture can best be cured by having constructive exercises. The boy who shows a natural tendency to destroy animal life may have the same arrested by being given the care of animals and thus having his sympathy developed. In other cases, the removal of stimuli, or conditions, for awaking the instinctive tendency will be found effective in checking the development of an undesirable instinct into a habit. The boy who shows a spirit of combativeness may be cured by having a generous and congenial boy as his chum. The pupil whose social tendencies are so strong that he cannot refrain from talking may be cured by isolation.
=Instincts May Disappear.=--In dealing with the instinctive tendencies of the child, it is important for the educator to remember that many of these are transitory in character and, if not utilized at the proper time, will perish for want of exercise. Even in the case of animals, natural instincts will not develop unless the opportunity for exercise is provided at the time. Birds shut up in a cage lose the instinct to fly; while ducks, after being kept a certain time from water, will not readily acquire the habit of swimming. In the same way, the child who is not given opportunity to a.s.sociate with others will likely grow up a recluse. All work for a few years, and it will be impossible for Jack to learn later how to play. The girl who during her childhood has no opportunity to display any pride through neatness in dress will grow up untidy and careless as to her personal appearance. In like manner, it is only the child whose constructive tendency is early given an opportunity to express itself who is likely to develop into an expert workman; while one who has no opportunity to give expression to his aesthetic instinct in early life will not later develop into an artist.
CURIOSITY
=Curiosity as Motive.=--An important bearing of instinct upon the work of education is found in the fact that an instinctive tendency may add much to the force of the motive, or end, in any educative process. This is especially true in the case of such adaptive instincts as curiosity, imitation, and play. Curiosity is the inquisitive att.i.tude, or appet.i.te, of the mind which causes it to seek out what is strange in its surroundings and make it an object of attention. As an instinctive tendency, its significance consists in the fact that it leads the individual to interpret his surroundings. A creature devoid of curiosity, therefore, would not discover either the benefits to be derived from his surroundings or the dangers to be avoided. In addition to its direct practical value in leading the individual to study his environment in order to meet actual needs, curiosity often seeks a more theoretic end, appearing merely as a feeling of wonder or a thirst for knowledge.
=Use and Abuse of Curiosity.=--While curiosity is needful for the welfare of the individual, an inordinate development of this instinct is both intellectually and morally undesirable. Since curiosity directs attention to the novel in our surroundings, over-curiosity is likely to keep the mind wandering from one novelty to another, and thus interfere with the fixing of attention for a sufficient time to give definiteness to particular impressions. The virtue of curiosity is, therefore, to direct attention to the novel until it is made familiar. There is a type of curiosity, however, which craves for mere astonishment and not for understanding. It is such curiosity that causes children to pry into other people"s belongings, and men into other people"s affairs.
=Sensuous and Apperceptive Curiosity.=--Curiosity may be considered of two kinds also from the standpoint of its origin. In early life, curiosity must rest largely upon sense perception, being essentially an appet.i.te of the senses to meet and interpret the objective surroundings.
A bright light, a loud noise, a moving object, at once awakens curiosity. At this stage, curiosity serves as a counteracting influence to the instinct of fear, the one leading the child to use his senses upon his surroundings, and the other causing him to use them in a careful and judicious manner. As the child grows in experience, however, his curiosity limits itself more and more in accordance with the law of apperception. Here the object attracts attention not merely because of its sensuous properties, but because it suggests novel relations within the elements of past experience. The young child"s curiosity, for instance, is aroused toward a strange plant simply because of its form and colour, that of the student of botany, because the plant presents features that do not relate themselves at once to his botanical experience. The first curiosity may be called objective, or sensuous, the second subjective, or apperceptive.
=Relation of Two Types.=--The distinction between sensuous and apperceptive curiosity is, of course, one of degree rather than one of kind. A novel object could not be an object of attention unless it bore some relation to the present mental content. The young child, however, seeks mainly to give meaning to novel sense impressions, and is not attracted to the more hidden relations in which objects may stand one to another. He is attracted, for instance, to the colour, scent, and general form of the flower, rather than to its structure. On the other hand, it is found that at a later stage curiosity is usually aroused toward a novel problem, to the extent to which the problem finds a setting in previous experience. This is seen in the fact that the young child takes no interest in having lessons grow out of each other in a connected manner, but must have his curiosity aroused to the present situation through its own intrinsic appeal. For this reason, young children are mainly interested in a lesson which deals with particular elements in a concrete manner, such as coloured blocks, bright pictures, and stories of action; while the older pupil seeks out the new problem because it stands in definite relation to what is already known.
=Importance of Apperceptive Curiosity.=--Since curiosity depends upon novelty, it is evident that sensuous should ultimately give place to apperceptive curiosity. Although objects first impress the senses with a degree of freshness and vigour, this freshness must disappear as the novelty of the impression wears off. When sensuous curiosity thus disappears, it is only by seeing in the world of sensuous objects other relations with their larger meaning, that healthy curiosity is likely to be maintained. Thus it is that the curiosity of the student is attracted to the more hidden qualities of objects, to the tracing of cause and effect, and to the discovery of scientific truth in general.
=Novelty versus Variety.=--While the familiar must lose something of its freshness through its very familiarity, it is to be noted that to remit any experience for a time will add something to the freshness of its revival. Persons and places, for instance, when revisited after a period of absence, gain something of the charm of novelty. Variety is, therefore, a means by which the effect of curiosity may be sustained, even after the original novelty has disappeared. This fact should be especially remembered in dealing with the studies of young children.