1. THE FUNCTION OF PERCEPTION

NEED OF KNOWING THE MATERIAL WORLD.--It is the business of perception to give us knowledge of our world of material _objects_ and their relations in _s.p.a.ce_ and _time_. The material world which we enter through the gateways of the senses is more marvelous by far than any fairy world created by the fancy of story-tellers; for it contains the elements of all they have conceived and much more besides. It is more marvelous than any structure planned and executed by the mind of man; for all the wonders and beauties of the Coliseum or of St. Peter's existed in nature before they were discovered by the architect and thrown together in those magnificent structures. The material advancement of civilization has been but the discovery of the objects, forces, and laws of nature, and their use in inventions serviceable to men. And these forces and laws of nature were discovered only as they were made manifest through objects in the material world.

The problem lying before each individual who would enter fully into this rich world of environment, then, is to discover at first hand just as large a part of the material world about him as possible. In the most humble environment of the most uneventful life is to be found the material for discoveries and inventions yet undreamed of. Lying in the shade of an apple tree under the open sky, Newton read from a falling apple the fundamental principles of the law of gravitation which has revolutionized science; sitting at a humble tea table Watt watched the gurgling of the steam escaping from the kettle, and evolved the steam engine therefrom; with his simple kite, Franklin drew down the lightning from the clouds, and started the science of electricity; through studying a ball, the ancient scholars conceived the earth to be a sphere, and Columbus discovered America.

THE PROBLEM WHICH CONFRONTS THE CHILD.--Well it is that the child, starting his life's journey, cannot see the magnitude of the task before him. Cast amid a world of objects of whose very existence he is ignorant, and whose meaning and uses have to be learned by slow and often painful experience, he proceeds step by step through the senses in his discovery of the objects about him. Yet, considered again, we ourselves are after all but a step in advance of the child. Though we are somewhat more familiar with the use of our senses than he, and know a few more objects about us, yet the knowledge of the wisest of us is at best pitifully meager compared with the richness of nature. So impossible is it for us to know all our material environment, that men have taken to becoming specialists. One man will spend his life in the study of a certain variety of plants, while there are hundreds of thousands of varieties all about him; another will study a particular kind of animal life, perhaps too minute to be seen with the naked eye, while the world is teeming with animal forms which he has not time in his short day of life to stop to examine; another will study the land forms and read the earth's history from the rocks and geological strata, but here again nature's volume is so large that he has time to read but a small fraction of the whole. Another studies the human body and learns to read from its expressions the signs of health and sickness, and to prescribe remedies for its ills; but in this field also he has found it necessary to divide the work, and so we have specialists for almost every organ of the body.

2. THE NATURE OF PERCEPTION

HOW A PERCEPT IS FORMED.--How, then, do we proceed to the discovery of this world of objects? Let us watch the child and learn the secret from him. Give the babe a ball, and he applies every sense to it to discover its qualities. He stares at it, he takes it in his hands and turns it over and around, he lifts it, he strokes it, he punches it and jabs it, he puts it to his mouth and bites it, he drops it, he throws it and creeps after it. He leaves no stone unturned to find out what that thing really is. By means of the _qualities_ which come to him through the avenues of sense, he constructs the _object_. And not only does he come to know the ball as a material object, but he comes to know also its uses. He is forming his own best definition of a ball in terms of the sensations which he gets from it and the uses to which he puts it, and all this even before he can name it or is able to recognize its name when he hears it. How much better his method than the one he will have to follow a little later when he goes to school and learns that "A ball is a spherical body of any substance or size, used to play with, as by throwing, kicking, or knocking, etc.!"

THE PERCEPT INVOLVES ALL RELATIONS OF THE OBJECT.--Nor is the case in the least different with ourselves. When we wish to learn about a new object or discover new facts about an old one, we do precisely as the child does if we are wise. We apply to it every sense to which it will afford a stimulus, and finally arrive at the object through its various qualities. And just in so far as we have failed to use in connection with it every sense to which it can minister, just in that degree will we have an incomplete perception of it. Indeed, just so far as we have failed finally to perceive it in terms of its functions or uses, in that far also have we failed to know it completely. Tomatoes were for many years grown as ornamental garden plants before it was discovered that the tomatoes could minister to the taste as well as to the sight. The clothing of civilized man gives the same sensation of texture and color to the savage that it does to its owner, but he is so far from perceiving it in the same way that he packs it away and continues to go naked. The Orientals, who disdain the use of chairs and prefer to sit cross-legged on the floor, can never perceive a chair just as we do who use chairs daily, and to whom chairs are so saturated with social suggestions and a.s.sociations.

THE CONTENT OF THE PERCEPT.--The percept, then, always contains a basis of _sensation_. The eye, the ear, the skin or some other sense organ must turn in its supply of sensory material or there can be no percept.

But the percept contains more than just sensations. Consider, for example, your percept of an automobile flashing past your windows. You really _see_ but very little of it, yet you _perceive_ it as a very familiar vehicle. All that your sense organs furnish is a more or less blurred patch of black of certain size and contour, one or more objects of somewhat different color whom you know to be pa.s.sengers, and various sounds of a whizzing, chugging or roaring nature. Your former experience with automobiles enables you to a.s.sociate with these meager sensory details the upholstered seats, the whirling wheels, the swaying movement and whatever else belongs to the full meaning of a motor car.

The percept that contained only sensory material, and lacked all memory elements, ideas and meanings, would be no percept at all. And this is the reason why a young child cannot see or hear like ourselves. It lacks the a.s.sociative material to give significance and meaning to the sensory elements supplied by the end-organs. The dependence of the percept on material from past experience is also ill.u.s.trated in the common statement that what one gets from an art exhibit or a concert depends on what he brings to it. He who brings no knowledge, no memory, no images from other pictures or music will secure but relatively barren percepts, consisting of little besides the mere sensory elements. Truly, "to him that hath shall be given" in the realm of perception.

THE ACCURACY OF PERCEPTS DEPENDS ON EXPERIENCE.--We must perceive objects through our motor response to them as well as in terms of sensations. The boy who has his knowledge of a tennis racket from looking at one in a store window, or indeed from handling one and looking it over in his room, can never know a tennis racket as does the boy who plays with it on the court. Objects get their significance not alone from their qualities, but even more from their use as related to our own activities.

Like the child, we must get our knowledge of objects, if we are to get it well, from the objects themselves at first hand, and not second hand through descriptions of them by others. The fact that there is so much of the material world about us that we can never hope to learn it all, has made it necessary to put down in books many of the things which have been discovered concerning nature. This necessity has, I fear, led many away from nature itself to books--away from the living reality of things to the dead embalming cases of words, in whose empty forms we see so little of the significance which resides in the things themselves. We are in danger of being satisfied with the _forms_ of knowledge without its _substance_--with definitions contained in words instead of in qualities and uses.

NOT DEFINITIONS, BUT FIRST-HAND CONTACT.--In like manner we come to know distance, form and size. If we have never become acquainted with a mile by actually walking a mile, running a mile, riding a bicycle a mile, driving a horse a mile, or traveling a mile on a train, we might listen for a long time to someone tell how far a mile is, or state the distance from Chicago to Denver, without knowing much about it in any way except word definitions. In order to understand a mile, we must come to know it in as many ways as possible through sense activities of our own.

Although many children have learned that it is 25,000 miles around the earth, probably no one who has not encircled the globe has any reasonably accurate notion just how far this is. For words cannot take the place of perceptions in giving us knowledge. In the case of shorter distances, the same rule holds. The eye must be a.s.sisted by experience of the muscles and tendons and joints in actually covering distance, and learn to a.s.sociate these sensations with those of the eye before the eye alone can be able to say, "That tree is ten rods distant." Form and size are to be learned in the same way. The hands must actually touch and handle the object, experiencing its hardness or smoothness, the way this curve and that angle feels, the amount of muscular energy it takes to pa.s.s the hand over this surface and along that line, the eye taking note all the while, before the eye can tell at a glance that yonder object is a sphere and that this surface is two feet on the edge.

3. THE PERCEPTION OF s.p.a.cE

Many have been the philosophical controversies over the nature of s.p.a.ce and our perception of it. The psychologists have even quarreled concerning whether we possess an _innate_ sense of s.p.a.ce, or whether it is a product of experience and training. Fortunately, for our present purpose we shall not need to concern ourselves with either of these controversies. For our discussion we may accept s.p.a.ce for what common sense understands it to be. As to our sense of s.p.a.ce, whatever of this we may possess at birth, it certainly has to be developed by use and experience to become of practical value. In the perception of s.p.a.ce we must come to perceive _distance_, _direction_, _size_, and _form_. As a matter of fact, however, size is but so much distance, and form is but so much distance in this, that, or the other direction.

THE PERCEIVING OF DISTANCE.--Unquestionably the eye comes to be our chief dependence in determining distance. Yet the muscle and joint senses give us our earliest knowledge of distance. The babe reaches for the moon simply because the eye does not tell it that the moon is out of reach. Only as the child reaches for its playthings, creeps or walks after them, and in a thousand ways uses its muscles and joints in measuring distance, does the perception of distance become dependable.

At the same time the eye is slowly developing its power of judging distance. But not for several years does visual perception of distance become in any degree accurate. The eye's perception of distance depends in part on the sensations arising from the muscles controlling the eye, probably in part from the adjustment of the lens, and in part from the retinal image. If one tries to look at the tip of his nose he easily feels the muscle strain caused by the required angle of adjustment. We come unconsciously to a.s.sociate distance with the muscle sensations arising from the different angles of vision. The part played by the retinal image in judging distance is easily understood in looking at two trees, one thirty feet and the other three hundred feet distant. We note that the nearer tree shows the _detail_ of the bark and leaves, while the more distant one lacks this detail. The nearer tree also reflects more _light_ and _color_ than the one farther away. These minute differences, registered as they are on the retinal image, come to stand for so much of distance.

The ear also learns to perceive distance through differences in the quality and the intensity of sound. Auditory perception of distance is, however, never very accurate.

THE PERCEIVING OF DIRECTION.--The motor senses probably give us our first perception of direction, as they do of distance. The child has to reach this way or that way for his rattle; turn the eyes or head so far in order to see an interesting object; twist the body, crawl or walk to one side or the other to secure his bottle. In these experiences he is gaining his first knowledge of direction.

Along with these muscle-joint experiences, the eye is also being trained. The position of the image on the retina comes to stand for direction, and the eye finally develops so remarkable a power of perceiving direction that a picture hung a half inch out of plumb is a source of annoyance. The ear develops some skill in the perception of direction, but is less dependable than the eye.

4. THE PERCEPTION OF TIME

The philosophers and psychologists agree little better about our sense of time than they do about our sense of s.p.a.ce. Of this much, however, we may be certain, our perception of time is subject to development and training.

NATURE OF THE TIME SENSE.--How we perceive time is not so well understood as our perception of s.p.a.ce. It is evident, however, that our idea of time is simpler than our idea of s.p.a.ce--it has less of content, less that we can describe. Probably the most fundamental part of our idea of time is _progression_, or change, without which it is difficult to think of time at all. The question then becomes, how do we perceive change, or succession?

If one looks in upon his thought stream he finds that the movement of consciousness is not uniformly continuous, but that his thought moves in pulses, or short rushes, so to speak. When we are seeking for some fact or conclusion, there is a moment of expectancy, or poising, and then the leap forward to the desired point, or conclusion, from which an immediate start is taken for the next objective point of our thinking.

It is probable that our sense of the few seconds of pa.s.sing time that we call the _immediate present_ consists of the recognition of the succession of these pulsations of consciousness, together with certain organic rhythms, such as heart beat and breathing.

NO PERCEPTION OF EMPTY TIME.--Our perception does not therefore act upon empty time. Time must be filled with a procession of events, whether these be within our own consciousness or in the objective world without.

All longer periods of time, such as hours, days, or years, are measured by the events which they contain. Time filled with happenings that interest and attract us seems short while pa.s.sing, but longer when looked back upon. On the other hand, time relatively empty of interesting experience hangs heavy on our hands in pa.s.sing, but, viewed in retrospect, seems short. A fortnight of travel pa.s.ses more quickly than a fortnight of illness, but yields many more events for the memory to review as the "filling" for time.

Probably no one has any very accurate feeling of the length, that is, the actual _duration_ of a year--or even of a month! We therefore divide time into convenient units, as weeks, months, years and centuries. This allows us to think of time in mathematical terms where immediate perception fails in its grasp.

5. THE TRAINING OF PERCEPTION

In the physical world as in the spiritual there are many people who, "having eyes, see not and ears, hear not." For the ability to perceive accurately and richly in the world of physical objects depends not alone on good sense organs, but also on _interest_ and the habit of _observation_. It is easy if we are indifferent or untrained to look at a beautiful landscape, a picture or a cathedral without _seeing_ it; it is easy if we lack interest or skill to listen to an orchestra or the myriad sounds of nature without _hearing_ them.

PERCEPTION NEEDS TO BE TRAINED.--Training in perception does not depend entirely on the work of the school. For the world about us exerts a constant appeal to our senses. A thousand sights, sounds, contacts, tastes, smells or other sensations, hourly throng in upon us, and the appeal is irresistible. We must in some degree attend. We must observe.

Yet it cannot be denied that most of us are relatively unskilled in perception; we do not know how, or take the trouble to observe. For example, a stranger was brought into the cla.s.sroom and introduced by the instructor to a cla.s.s of fifty college students in psychology. The cla.s.s thought the stranger was to address them, and looked at him with mild curiosity. But, after standing before them for a few moments, he suddenly withdrew, as had been arranged by the instructor. The cla.s.s were then asked to write such a description of the stranger as would enable a person who had never seen him to identify him. But so poor had been the observation of the cla.s.s that they ascribed to him clothes of four different colors, eyes and hair each of three different colors, a tie of many different hues, height ranging from five feet and four inches to over six feet, age from twenty-eight to forty-five years, and many other details as wide of the mark. Nor is it probable that this particular cla.s.s was below the average in the power of perception.

SCHOOL TRAINING IN PERCEPTION.--The school can do much in training the perception. But to accomplish this, the child must constantly be brought into immediate contact with the physical world about him and taught to observe. Books must not be subst.i.tuted for things. Definitions must not take the place of experiment or discovery. Geography and nature study should be taught largely out of doors, and the lessons a.s.signed should take the child into the open for observation and investigation. All things that live and grow, the sky and clouds, the sunset colors, the brown of upturned soil, the smell of the clover field, or the new mown hay, the sounds of a summer night, the distinguishing marks by which to identify each family of common birds or breed of cattle--these and a thousand other things that appeal to us from the simplest environment afford a rich opportunity for training the perception. And he who has learned to observe, and who is alert to the appeal of nature, has no small part of his education already a.s.sured.

6. PROBLEMS IN OBSERVATION AND INTROSPECTION

1. Test your power of observation by walking rapidly past a well-filled store window and then seeing how many of the objects you can name.

2. Suppose a tailor, a bootblack, a physician, and a detective are standing on the street corner as you pa.s.s by. What will each one be most likely to observe about you? _Why?_

3. Observe carefully green trees at a distance of a few rods; a quarter of a mile; a mile; several miles. Describe differences (1) in color, (2) in brightness, or light, and (3) in detail.

4. How many common birds can you identify? How many kinds of trees? Of wild flowers? Of weeds?

5. Observe the work of an elementary school for the purpose of determining:

a. Whether the instruction in geography, nature study, agriculture, etc., calls for the use of the eyes, ears and fingers.

b. Whether definitions are used in place of first-hand information in any subjects.

c. Whether the a.s.signment of lessons to pupils includes work that would require the use of the senses, especially out of doors.

d. Whether the work offered in arithmetic demands the use of the senses as well as the reason.

e. Whether the language lessons make use of the power of observation.

CHAPTER VIII

MENTAL IMAGES AND IDEAS