Ontario Normal School Manuals: Science of Education Part 21

ATTENTION IN EDUCATION

=Voluntary Attention and Learning.=--From what has been seen, it is evident that, when a pupil in his school approaches any particular problem, the learning process will represent a process of voluntary attention. This form of attention is, therefore, one of special significance to the teacher, since a knowledge of the process will cast additional light upon the learning process. The first condition of voluntary attention is the power to select some idea as an end, or problem, for attention. It was seen, however, that the focusing of attention upon any problem depends upon some form of desirable change to be effected in and through the set problem. For instance, unless the recovery of the coin is conceived as producing a desirable change, it would not become a deliberately set problem for attention. It is essential, therefore, that the end which the child is to choose as an object of attention should be one conceived as demanding a desired change, or adjustment. For instance, to ask a child to focus his attention upon two pieces of wood merely as pieces of wood is not likely to call forth an active effort of attention. To direct his attention to them to find out how many times the one is contained in the other, on the other hand, focuses his attention more strongly upon them; since the end to be reached will awaken his curiosity and set an interesting problem.

=Non-voluntary Attention in Education.=--On account of the ease with which attention seems to centre itself upon its object in non-voluntary attention, it is sometimes erroneously claimed that this is the type of attention to be aimed at in the educative process, especially with young children. Such a view is, however, a fallacious one, and results from a false notion of the real character of both non-voluntary and voluntary attention. In a clear example of non-voluntary attention, the mind dwells upon the ideas merely on account of their inherent attractiveness, and pa.s.ses from one idea to its a.s.sociated idea without any purposeful end in view. This at once shows its ineffectiveness as a process of learning. When the young lover's thoughts revert in a non-voluntary way to the fair one, he perhaps pa.s.ses into a state of mere reminiscence, or at best of idle fancy. Even the student whose thoughts run on in a purposeless manner over his favourite subject, will merely revive old a.s.sociations, or at best make a chance discovery of some new knowledge. In the same way, the child who delights in musical sounds may be satisfied to drum the piano by the hour, but this is likely to give little real advance, unless definite problems are set up and their attainment striven for in a purposeful way.

=Voluntary Attention and Interest.=--A corollary of the fallacy mentioned above is the a.s.sumption that voluntary attention necessarily implies some conflict with the mind's present desire or interest. It is sometimes said, for instance, that in voluntary attention, we compel our mind to attend, while our interest would naturally direct our attention elsewhere. But without a desire to effect some change in or through the problem being attended to, the mind would not voluntarily make it an object of attention. The misconception as to the relation of voluntary attention to interest is seen in an ill.u.s.tration often given as an example of non-voluntary attention. It is said, rightly enough, that if a child is reading an interesting story, and is just at the point where the plot is about to unravel itself, there will be difficulty in diverting his attention to other matters. This, it is claimed, furnishes a good example of the power of non-voluntary attention. But quite the opposite may be the case. When called upon, say by his parent, to lay aside the book and attend to some other problem, the child, it is true, shows a desire to continue reading. But this may be because he has a definite aim of his own in view--to find out the fate of his hero. This is a strongly felt need on his part, and his mind refuses to be satisfied until, by further attention to the problem before him, he has attained to this end. The only element of truth in the ill.u.s.tration is that the child's attention is strongly reinforced through the intense feeling tone a.s.sociated with the selected, or determined, aim--the fate of his hero. The fact is, therefore, that a process of voluntary attention may have a.s.sociated with its problem as strong an interest as is found in the non-voluntary type.

=Voluntary Attention Depends on Problem.=--It is evident from the foregoing that the characteristic of voluntary attention is not the absence or the presence of any special degree of interest, but rather the conception of some end, or purpose, to be reached in and through the attentive process. In other words, voluntary attention is a state of mind in which the mental movements are not drifting without a chart, but are seeking to reach a set haven. A person who is greatly interested in automobiles, for instance, on seeing a new machine, may allow his attention to run now to this part of the machine, now to that, as each attracts him in turn. Here no fixed purpose is being served by the attentive process, and attention may pa.s.s from part to part in a non-voluntary way, the person's general interest in automobiles being sufficient to keep the attention upon the subject. Suddenly, however, he may notice something apparently new in the mechanism of the machine, and a desire arises to understand its significance. This at once becomes an end to which the mind desires to attain, and voluntary attention proceeds to direct the mental movements toward its attainment. To suppose, however, that the interest, manifest in the former mental movements, is now absent, would evidently be fallacious. The difference lies in this, that at first the attention seemed fixed on the object through a general interest only, and drifted from point to point in a purposeless way, while in the second case an interesting end, or purpose, controlled the mental movements, and therefore made each movement significant in relation to the whole conscious process.

=Attention and Knowledge.=--Mention has already been made of the relation of attention to interest. It should be noted, further, that the difference in our attention under different circ.u.mstances is largely dependent upon our knowledge. The stonecutter, as he pa.s.ses the fine mansion, gives attention to the fretted cornice; the glazier, to the beautiful windows; the gardener, to the well-kept lawn and beds. Even the present content of the mind has its influence upon attention. The student on his way to school, if busy with his spelling lesson, is attracted to the words and letters on posters and signs. If he is reviewing his botany, he notes especially the weeds along the walk; if carrying to his art teacher, with a feeling of pride, the finished landscape drawing, his attention goes out to the shade and colour of field and sky. That such a connection must exist between knowledge and attention is apparent from what has been already noted concerning the working of the law of apperception.

=Physical Conditions of Attention.=--From what was learned above regarding the relation of nervous energy to active attention, it is evident that the ability to attend to a problem at any given time will depend in part upon the physical condition of the organism. If, therefore, the nervous energy is lowered through fatigue or sickness, the attention will be weakened. For this reason the teaching of subjects, such as arithmetic, grammar, etc., which present difficult problems, and therefore make large demands upon the attention of the scholars, should not be undertaken when the pupils' energy is likely to be at a minimum. Similarly, unsatisfactory conditions in the school-room, such as poor ventilation, uncomfortable seats, excessive heat or cold, all tend to lower the nervous energy and thus prevent a proper concentration of attention upon the regular school work.

=Precautions Relating to Voluntary Attention.=--Although voluntary attention is evidently the form of attention possessing real educational value, certain precautions would seem necessary concerning its use. With very young children the aim for attending should evidently not be too remote. In other words, the problem should involve matter in which the children have a direct interest. For this reason it is sometimes said that young children should set their own problems. This is of course a paradox so far as the regular school work is concerned, though it does apply to the pre-school period, and also justifies the claim that with young children the lesson problem should be closely connected with some vital interest. It would be useless, for instance, to try to interest young children in the British North America Act by telling them that the knowledge will be useful when they come to write on their entrance examinations. The story of Sir Isaac Brock, on the other hand, wins attention for itself through the child's patriotism and love of story.

Again, the problem demanding attention should not, in the case of young children, be too long or complex. For example, a young child might easily attend to the separate problems of finding out, (1) how many marbles he must have to give four to James and three to William; (2) how many times seven can be taken from twenty-eight; (3) how many marbles James would have if he received four marbles four times; and (4) how many James would have if he received three marbles three times. But if given the problem "to divide twenty-eight marbles between James and William, giving James four every time he gives William three," the problem may be too complex for his present power of attention. A young child has not the control over his knowledge necessary to continue any long process of selecting attention. A relatively short period of attention to any problem, therefore, exhausts the nervous energy in the centres connected with a particular set of experiences. It is for this reason that the lessons in primary cla.s.ses should be short and varied.

One of the objections, therefore, to a narrow curriculum is that attention would not obtain needed variety, and that a narrowness in interest and application may result. On the other hand, it is well to note that the child must in time learn to concentrate his attention for longer periods and upon topics possessing only remote, or indirect, interest.

CHAPTER XXIV

THE FEELING OF INTEREST

=Nature of Feeling.=--Feeling has already been described (Chapter XIX) as the pleasurable or painful side of any state of consciousness. We may recall how it was there found that any conscious state, or experience, for instance, being conscious of the p.r.i.c.k of a pin, of success at an examination, or of the loss of a friend, is not merely a state of knowledge, or awareness, but is also a state of feeling. It is a state of feeling because it _affects_ us, that is, because being a state of _our_ consciousness, it appeals to us pleasurably or painfully in a way that it can to no one else.

=Neural Conditions of Feeling.=--It has been seen that every conscious state, or experience, has its affective, or feeling, tone, and also that every experience involves the transmission of nervous energy through a number of connected brain cells. On this basis it is thought that the feeling side of any conscious state is conditioned by the degree of the resistance encountered as the nervous energy is transmitted. If the centres involved in the experience are not yet properly organized, or if the stimulation is strong, the resistance is greater and the feeling more intense. A new movement of the limbs in physical training, for example, may at first prove intensely painful, because the centres involved in the exercise are not yet organized. So also, because a very bright light stimulates the nerves violently, it causes a painful feeling. That morphine deadens pain is to be explained on the a.s.sumption that it decreases nervous energy, and thus lessens the resistance being encountered between the nervous centres affected at the time.

=Feeling and Habit.=--That the intensity of a feeling is conditioned by the amount of the resistance seems evident, if we note the relation of feeling to habit. The first time the nurse-in-training attends a wounded patient, the experience is marked by intense feeling. After a number of such experiences, however, this feeling becomes much less. In like manner, the child who at first finds the physical exercise painful, as he becomes accustomed to the movements, finds the pain becoming less and less intense. In such cases it is evident that practice, by organizing the centres involved in the experience, decreases the resistance between them, and thus gradually decreases the intensity of the feeling. When finally the act becomes habitual, the nervous impulse traverses only lower centres, and therefore all feeling and indeed all consciousness will disappear, as happens in the habitual movements of the limbs in walking and of the arms during walking.

CLa.s.sES OF FEELINGS

=Sensuous Feeling.=--As already noted, while feelings vary in intensity according to the strength of the resistance, they also differ in kind according to the arcs traversed by the impulse. Experiencing a burn on the hand would involve nervous impulses, or currents, other than those involved in hearing of the death of a friend. The one experience also differs in feeling from the other. Our feeling states are thus able to be divided into certain important cla.s.ses with more or less distinct characteristics for each. In one cla.s.s are placed those feelings which accompany sensory impulses. The sensations arising from the stimulations of the sense organs, as a sweet or bitter taste, a strong smell, the touch of a hot, sharp, rough, or smooth object, etc., all present an affective, or feeling, side. So also feeling enters into the general or organic sensations arising from the conditions of the bodily organs; as breathing, the circulation of the blood, digestion, the tension of the muscles, hunger, thirst, etc. The feeling which thus enters as a factor into any sensation is known as sensuous feeling.

=Ideal Feeling.=--Other feelings enter into our ideas and thoughts. The perception or imagination of an accident is accompanied with a painful feeling, the memory or antic.i.p.ation of success with a feeling of joy, the thought of some particular person with a thrill of love. Such feelings are known as ideal feelings. When a child tears his flesh on a nail, he experiences sensuous feeling, when he shrinks away, as he perceives the teeth of a snarling dog, he experiences an ideal feeling, known as the emotion of fear.

=Interest.=--A third type of feeling especially accompanies an active process of attention. In our study of attention, it was seen that any process of attention is accompanied by a concentration of nervous energy upon the paths or centres involved in the experience, thus organizing the paths more completely and thereby decreasing the resistance. The impulse to attend to any experience is, therefore, accompanied with a desirable feeling, because a new adjustment between nerve centres is taking place and resistance being overcome. This affective, or feeling, tone which accompanies a process of attention is known as the feeling of interest.

=Interest and Attention.=--In discussions upon educational method, it is usually affirmed that the attention will focus upon a problem to the extent to which the mind is interested. While this statement may be accepted in ordinary language, it is not psychologically true that I first become interested in a strange presentation, and then attend to it afterwards. In such a case it is no more true to say that I attend because I am interested, than to say that I am interested because I attend. In other words, interest and attention are not successive but simultaneous, or, as sometimes stated, they are back and front of the same mental state. This becomes evident by noting the nervous conditions which must accompany interest and attention. When one is attending to any strange phenomenon, say a botanist to the structure of a rare plant, it is evident that there are not only new groupings of ideas in the mind, but also new adjustments being set up between the brain centres.

This implies in turn a lessening of resistance between the cells, and therefore the presence of the feeling tone known as interest.

=Interest, Attention, and Habit.=--Since the impulse to attend to a presentation is conditioned by a process of adjustment, or organization, between brain centres, it is evident that, while the novel presentations call forth interest and attention, repet.i.tion, by habituating the nervous arcs, will tend to deaden interest and attention. For this reason the story, first heard with interest and attention, becomes stale by too much repet.i.tion. The new toy fails to interest the child after the novelty has worn off. It must be noted, however, that while repet.i.tion usually lessens interest, yet when any set of experiences are repeated many times, instead of lessening interest the repet.i.tion may develop a new interest known as the interest of custom. Thus it is that by repeating the experience the man is finally compelled to visit his club every evening, and the boy to play his favourite game every day.

This secondary interest of custom arises because repet.i.tion has finally established such strong a.s.sociations within the nervous system that they now have become a part of our nature and are thus able to make a new demand upon interest and attention.

INTEREST IN EDUCATION

=Uses of Term: A. Subjective; B. Objective.=--That the educator describes interest as something that causes the mind to give attention to what is before it, when in fact interest and attention are psychologically merely two sides of a single process, is accounted for by the fact that the term "interest" may be used with two quite different meanings. Psychologically, interest is evidently a feeling state, that is, it represents a phase of consciousness. My _interest_ in football, for instance, represents the _feeling_ of worth which accompanies attention to such experiences. In this sense interest and attention are but two sides of the single experience, interest representing the feeling, and attention the effort side of the experience. As thus applied, the term interest is said to be used subjectively. More, often, however, the term is applied rather to the thing toward which the mind directs its attention, the object being said to possess interest for the person. In this sense the rattle is said to have interest for the babe; baseball, for the young boy; and the latest fashions, for the young lady. Since the interest is here a.s.sumed to reside in the object, it seems reasonable to say that our attention is attracted through interest, that is, through an interesting presentation. As thus applied, the term interest is said to be used objectively.

=Types of Objective Interest.=--The interest which various objects and occupations thus possess for the mind may be of two somewhat different types. In some cases the object possesses a direct, or intrinsic, interest for the mind. The young child, for instance, is spontaneously attracted to bright colours, the boy to stories of adventure, and the sentimental youth or maiden to the romance. In the case of any such direct interests, however, the feeling with which the mind contemplates the object may transfer itself at least partly to other objects a.s.sociated more or less closely with the direct object of interest. It is thus that the child becomes interested in the cup from which his food is taken, and the lover in the lap dog which his fair one fondles. As opposed to the _direct interest_ which an object may have for the mind, this transferred type is known as _indirect interest_.

=Importance of Transference of Interest.=--The ability of the mind thus to transfer its interests to a.s.sociated objects is often of great pedagogical value. Abstract forms of knowledge become more interesting to young children through being a.s.sociated with something possessing natural interest. A pupil who seems to take little interest in arithmetic may take great delight in manual training. By a.s.sociating various mathematical problems with his constructive exercises, the teacher can frequently cause the pupil to transfer in some degree his primary interest in manual training to the a.s.sociated work in arithmetic. In the same way the child in the primary grade may take more delight in the alphabet when he is able to make the letters in sand or by stick-laying. It may be said, in fact, that much of man's effort is a result of indirect interest. What is called doing a thing from a sense of duty is often a case of applying ourselves to a certain thing because we are interested in avoiding the disapproval of others. The child also often applies himself to his tasks, not so much because he takes a direct interest in them, but because he wishes to gain the approval and avoid the censure of teacher and parents.

=Native and Acquired Interest.=--Interest may also be distinguished on the basis of its origin. As noted above, certain impressions seem to demand a spontaneous interest from the individual. For this cause the child finds his attention going out immediately to bright colours, to objects which give pleasure, such as candy, etc., or to that which causes personal pain. On the other hand, objects and occupations which at first seem devoid of interest may, after a certain amount of experience has been gained, become important centres of interest. A young child may at first show no interest in insects unless it be a feeling of revulsion. Through the visit of an entomologist to his home, however, he may gain some knowledge of insects. This knowledge, by arousing an apperceptive tendency in the direction of insect study, gradually develops in him a new interest which lasts throughout his whole life. It is in this way that the various school subjects widen the narrow interests of the child. By giving him an insight into various phases of his social environment, the school curriculum awakens in him different centres of interest, and thus causes him to become in the truest sense a part of the social life about him. This fact is one of the strongest arguments, also, against a narrow public school course of study in a society which is itself a complex of diversified interests.

=Interest versus Interests.=--On account of the evident connection of interest and attention, the teacher may easily err in dealing with the young pupil. It is allowable, as pointed out above, that the teacher should take advantage of any native interest to secure the attention and effort of the child in his school work. This does not mean, however, that children are to be given only problems in which they are naturally interested. It must be remembered, as seen in a former paragraph, that, according to the interest of custom, any line of school work, when intelligently followed, may soon build up a centre of interest for itself. For this reason a proper study of arithmetic should develop an interest in arithmetic; a study of history, an interest in history; and a study of geography, an interest in geography. The saying that school work should follow a child's interest might, therefore, be better expressed by saying that the child's interests should follow the school work. It is only, in fact, as any one becomes directly interested in his pursuits, that the highest achievement can be reached. It is not the workman who is always looking forward to pay-day, who develops into an artist, or the teacher who is waiting for the summer holiday, who is a real inspiration to her pupils. In like manner, it is only as the child forms centres of interest in connection with his school work, that his life and character are likely to be affected permanently thereby.

=Development of Interests.=--The problem for the educator is, therefore, not so much to follow the interest of the child, as it is to develop in him permanent centres of interest. For this reason the following facts concerning the origin and development of interests should be understood by the practical educator. First among these is the fact that certain instinctive tendencies of early childhood may be made a starting-point for the development of permanent valuable interest. The young child has a tendency to collect or an instinct of ownership, which may be taken advantage of in directing him to make collections of insects, plants, coins, stamps, and thus prove of permanent educative value. His constructive tendencies, or desire to do with what comes into his hand, as well as his imitative instincts, may be turned to account in building up an interest in various occupations. His social instinct, also, provides a means for developing permanent emotional interests as sympathy, etc. In like manner, the character of the child's surroundings tends to create in him various centres of interest. The young child, for instance, who is surrounded with beautiful objects, is almost sure to develop an interest in works of art, while the child who is early provided with fable and story will develop an interest in history.

=When to Develop Interests.=--It is to be noted further concerning many of these forms of interest, that youth is the special period for their development. The child who does not, during his early years, have an opportunity to develop his social tendencies, is not likely later in life to acquire an interest in his fellow-men. In the same manner, if youth is spent in surroundings void of aesthetic elements, manhood will be lacking in artistic interests. It is in youth also that our intellectual interests, such as love of reading, of the study of nature, of mathematics, must be laid.

=Interests Must be Limited.=--While emphasizing the importance of establishing a wide range of interests when educating a child, the teacher must remember that there is danger in a child acquiring too wide a range. This can result only in a dissipation of effort over many fields. While this prevents narrowness of vision and gives versatility of disposition, it may prevent the attainment of efficiency in any department, and make of the youth the proverbial "Jack-of-all-trades."

A study of the feeling of interest has been made at this stage on account of its close connection with the problem of attention, and in fact with the whole learning process. An examination of the other cla.s.ses of feeling will be made at a later stage in the course.

CHAPTER XXV

SENSE PERCEPTION

=Sensation and Perception Distinguished.=--Sensation and perception are two terms applied usually without much distinction of meaning to our recognition of the world of objects. When, for instance, a man draws near to a stove, he may say that it gives him a _sensation_ of heat, or perhaps that he _perceives_ it to be hot. In psychology, however, the term sensation has been used in two somewhat different meanings. By some the term is used to signify a state of consciousness conditioned merely upon the stimulation of a sense organ, as the eye, ear, etc., by its appropriate stimulus. To others, however, sensation signifies rather a mental image experienced by the mind as it reacts upon and interprets any sensory impression. Perception, on the other hand, signifies the recognition of an external object as presented to the mind here and now.

=Sensation Implies Externality.=--When, however, a sensory image, such as smooth, yellow, cold, etc., arises in consciousness as a result of the mind reacting when an external stimulus is applied to some sense organ, it is evident that, at least after very early infancy, one never has the image without at once referring it to some external cause. If, for instance, a person is but half awake and receives a sound sensation, he does not ask himself, "What mental state is _this_?" but rather, "What is _that_?" This shows an evident tendency to refer our sensations at once to an external cause, or indicates that our sensations always carry with them an implicit reference to an external object. Leaving, therefore, to the scientific psychologist to consider whether it is possible to have a pure sensation, we shall treat sensation as the recognition of a quality which is at least vaguely referred to an external object. In other words, sensation is a medium by which we are brought into relation with real things existing independently of our sensations.

=Perception Involves Sensation Element.=--Moreover, an object is perceived as present here and now only because it is revealed to us through one or more of the senses. When, for instance, I reach out my hand in the dark room and receive a sensation of touch, I perceive the table as present before me. When I receive a sensation of sound as I pa.s.s by the church, I perceive that the organ is being played. When I receive a colour sensation from the store window, I say that I perceive oranges. Perception, therefore, involves the referring of the sensuous state, or image, to an external thing, while in adult life sensation is never accepted by our attention as satisfactory unless it is referred to something we regard as immediately presenting itself to us by means of the sensation. It is on account of this evident interrelation of the two that we speak of a process of sense perception.

=Perception an Acquired Power.=--On the other hand, however, investigation will show that this power to recognize explicitly the existence of an external object through the presentation of a sensation, was not at first possessed by the mind. The ability thus to perceive objects represents, therefore, an acquirement on the part of the individual. If a person, although receiving merely sensations of colour and light, is able to say, "Yonder is an orange," he is evidently interpreting, or giving meaning to, the present sensations largely through past experience; for the images of colour and light are accepted by the mind as an indication of the presence of an external thing from which could be derived other images of taste, smell, etc., all of which go to make up the idea "orange." An ordinary act of perception, therefore, must involve not merely sensation, but also an interpretation of sensation through past experience. It is, in fact, because the recognition of an external object involves this conscious interpretation of the sensuous impressions, that people often suffer delusion. When the traveller pa.s.sing by a lone graveyard interprets the tall and slender shrub laden with white blossoms as a swaying ghost, the misconception does not arise from any fault of mere vision, but from the type of former knowledge which the other surroundings of the moment call up, these evidently giving the mind a certain bias in its interpretation of the sensuous, or colour, impressions.

=Perception in Adult Life.=--In our study of general method, sense perception was referred to as the most common mode of acquiring particular knowledge. A description of the development of this power to perceive objects through the senses should, therefore, prove of pedagogical value. But to understand how an individual acquires the ability to perceive objects, it is well to notice first what takes place in an ordinary adult act of perception, as for instance, when a man receives and interprets a colour stimulus and says that he perceives an orange. If we a.n.a.lyse the person's idea of an orange we find that it is made up of a number of different quality images--colour, taste, smell, touch, etc., organized into a single experience, or idea, and accepted as a mental representation of an object existing in s.p.a.ce. When, therefore, the person referred to above says that he perceives an orange, what really happens is that he accepts the immediate colour and light sensation as a sign of the whole group of qualities which make up his notion of the external object, orange, the other qualities essential to the notion coming back from past experience to unite with the presented qualities. Owing to this fact, any ordinary act of perception is said to contain both presentative and representative elements. In the above example, for instance, the colour would be spoken of as a presentative element, because it is immediately presented to the mind in sensuous terms, or through the senses. Anything beyond this which goes to make up the individual's notion orange, and is revived from past experience, is spoken of as representative. For the same reason, the sensuous elements involved in an ordinary act of perception are often spoken of as immediate, and the others as mediate elements of knowledge.

=Genesis of Perception.=--To trace the development of this ability to mingle both presentative and representative elements of knowledge into a mental representation, or idea, of an external object, it is necessary to recall what has been noted regarding the relation of the nervous system to our conscious acts. When the young child first comes in contact with the world of strange objects with which he is surrounded, the impressions he receives therefrom will not at first have either the definite quality or the relation to an external thing which they later secure. As a being, however, whose first tendencies are those of movement, he grasps, bites, strokes, smells, etc., and thus goes out to meet whatever his surroundings thrust upon him. Gradually he finds himself expand to take in the existence of a something external to himself, and is finally able, as the necessary paths are laid down in his nervous system, to differentiate various quality images one from the other; as, touch, weight, temperature, light, sound, etc. This will at once involve, however, a corresponding relating, or synthetic, att.i.tude of mind, in which different quality images, when experienced together as qualities of some vaguely felt thing, will be organized into a more or less definite knowledge, or idea, of that object, as ill.u.s.trated in the figure below. As the child in time gains the ability to _attend_ to the sensuous presentations which come to him, and to discriminate one sensation from another, he discovers in the vaguely known thing the images of touch, colour, taste, smell, etc., and finally a.s.sociates them into the idea of a better known object, orange.

[Ill.u.s.tration: A. Unknown thing. B. Sensory stimuli. C. Sensory images.

D. Idea of object.]

=Control of Sensory Image as Sign.=--Since the various sense impressions are carried to the higher centres of the brain, they will not only be interpreted as sensory images and organized into a knowledge of external objects, but, owing to the retentive power of the nervous tissue, will also be subject to recall. As the child thus gains more and more the ability to organize and relate various sensory images into mental representations, or ideas, of external objects, he soon acquires such control over these organized groups, that when any particular sensation image out of a group is presented to the mind, it will be sufficient to call up the other qualities, or will be accepted as a sign of the presence of the object. When this stage of perceptual power is reached, an odour coming from the oven enables a person to perceive that a certain kind of meat is within, or a noise proceeding from the tower is sufficient to make known the presence of a bell. To possess the ability thus to refer one's sensations to an external object is to be able to perceive objects.

=Fulness of Perception Based on Sensation.=--From the foregoing account of the development of our perception of the external world, it becomes evident that our immediate knowledge, or idea, of an individual object will consist only of the images our senses have been able to discover either in that or other similar objects. To the person born without the sense of sight, for instance, the flower-bed can never be known as an object of tints and colours. To the person born deaf, the violin cannot really be known as a _musical_ instrument. Moreover, only the person whose senses distinguish adequately variations in colour, sound, form, etc., is able to perceive fully the objects which present themselves to his senses. Even when the physical senses seem equally perfect, one man, through greater power of discrimination, perceives in the world of objects much that totally escapes the observation of another. The result is that few of us enter as fully as we might into the rich world of sights, sounds, etc., with which we are surrounded, because we fail to gain the abundant images that we might through certain of our senses.

FACTORS INVOLVED IN SENSATION