As you sit thinking, a company of you together, your thoughts run in many diverse lines. Yet with all this diversity, your minds possess this common characteristic: Though your thinking all takes place in what we call the present moment, it goes on largely in terms of past experiences.

1. THE PART PLAYED BY PAST EXPERIENCE

Present Thinking Depends on Past Experience.—Images or ideas of things you have seen or heard or felt; of things you have thought of before and which now recur to you; of things you remember, such as names, dates, places, events; of things that you do not remember as a part of your past at all, but that belong to it nevertheless—these are the things which form a large part of your mental stream, and which give content to your thinking. You may think of a thing that is going on now, or of one that is to occur in the future; but, after all, you are dependent on your past experience for the material which you put into your thinking of the present moment.

Indeed, nothing can enter your present thinking which does not link itself to something in your past experience. The savage Indian in the primeval forest never thought about killing a deer with a rifle merely by pulling a trigger, or of turning a battery of machine guns on his enemies to annihilate them—none of these things were related to his past experience; hence he could not think in such terms.

The Present Interpreted by the Past.—Not only can we not think at all except in terms of our past experience, but even if we could, the present would be meaningless to us; for the present is interpreted in the light of the past. The sedate man of affairs who decries athletic sports, and has never taken part in them, cannot understand the wild enthusiasm which prevails between rival teams in a hotly contested event. The fine work of art is to the one who has never experienced the appeal which comes through beauty, only so much of canvas and variegated patches of color. Paul says that Jesus was "unto the Greeks, foolishness." He was foolishness to them because nothing in their experience with their own gods had been enough like the character of Jesus to enable them to interpret Him.

The Future Also Depends on the Past.—To the mind incapable of using past experience, the future also would be impossible; for we can look forward into the future only by placing in its experiences the elements of which we have already known. The savage who has never seen the shining yellow metal does not dream of a heaven whose streets are paved with gold, but rather of a "happy hunting ground." If you will analyze your own dreams of the future you will see in them familiar pictures perhaps grouped together in new forms, but coming, in their elements, from your past experience nevertheless. All that would remain to a mind devoid of a past would be the little bridge of time which we call the "present moment," a series of unconnected nows. Thought would be impossible, for the mind would have nothing to compare and relate. Personality would not exist; for personality requires continuity of experience, else we should be a new person each succeeding moment, without memory and without plans. Such a mind would be no mind at all.

Rank Determined by Ability to Utilize Past Experience.—So important is past experience in determining our present thinking and guiding our future actions, that the place of an individual in the scale of creation is determined largely by the ability to profit by past experience. The scientist tells us of many species of animals now extinct, which lost their lives and suffered their race to die out because when, long ago, the climate began to change and grow much colder, they were unable to use the experience of suffering in the last cold season as an incentive to provide shelter, or move to a warmer climate against the coming of the next and more rigorous one. Man was able to make the adjustment; and, providing himself with clothing and shelter and food, he survived, while myriads of the lower forms perished.

The singed moth again and again dares the flame which tortures it, and at last gives its life, a sacrifice to its folly; the burned child fears the fire, and does not the second time seek the experience. So also can the efficiency of an individual or a nation, as compared with other individuals or nations, be determined. The inefficient are those who repeat the same error or useless act over and over, or else fail to repeat a chance useful act whose repetition might lead to success. They are unable to learn their lesson and be guided by experience. Their past does not sufficiently minister to their present, and through it direct their future.

2. HOW PAST EXPERIENCE IS CONSERVED

Past Experience Conserved in Both Mental and Physical Terms.—If past experience plays so important a part in our welfare, how, then, is it to be conserved so that we may secure its benefits? Here, as elsewhere, we find the mind and body working in perfect unison and harmony, each doing its part to further the interests of both. The results of our past experience may be read in both our mental and our physical nature.

On the physical side past experience is recorded in modified structure through the law of habit working on the tissues of the body, and particularly on the delicate tissues of the brain and nervous system. This is easily seen in its outward aspects. The stooped shoulders and bent form of the workman tell a tale of physical toil and exposure; the bloodless lips and pale face of the victim of the city sweat shop tell of foul air, long hours, and insufficient food; the rosy cheek and bounding step of childhood speak of fresh air, good food and happy play.

On the mental side past experience is conserved chiefly by means of images, ideas, and concepts. The nature and function of concepts will be discussed in a later chapter. It will now be our purpose to examine the nature of images and ideas, and to note the part they play in the mind's activities.

The Image and the Idea.—To understand the nature of the image, and then of the idea, we may best go back to the percept. You look at a watch which I hold before your eyes and secure a percept of it. Briefly, this is what happens: The light reflected from the yellow object, on striking the retina, results in a nerve current which sets up a certain form of activity in the cells of the visual brain area, and lo! a percept of the watch flashes in your mind.

Now I put the watch in my pocket, so that the stimulus is no longer present to your eye. Then I ask you to think of my watch just as it appeared as you were looking at it; or you may yourself choose to think of it without my suggesting it to you. In either case the cellular activity in the visual area of the cortex is reproduced approximately as it occurred in connection with the percept, and lo! an image of the watch flashes in your mind. An image is thus an approximate copy of a former percept (or several percepts). It is aroused indirectly by means of a nerve current coming by way of some other brain center, instead of directly by the stimulation of a sense organ, as in the case of a percept.

If, instead of seeking a more or less exact mental picture of my watch, you only think of its general meaning and relations, the fact that it is of gold, that it is for the purpose of keeping time, that it was a present to me, that I wear it in my left pocket, you then have an idea of the watch. Our idea of an object is, therefore, the general meaning of relations we ascribe to it. It should be remembered, however, that the terms image and idea are employed rather loosely, and that there is not yet general uniformity among writers in their use.

All Our Past Experience Potentially at Our Command.—Images may in a certain sense take the place of percepts, and we can again experience sights, sounds, tastes, and smells which we have known before, without having the stimuli actually present to the senses. In this way all our past experience is potentially available to the present. All the objects we have seen, it is potentially possible again to see in the mind's eye without being obliged to have the objects before us; all the sounds we have heard, all the tastes and smells and temperatures we have experienced, we may again have presented to our minds in the form of mental images without the various stimuli being present to the end-organs of the senses.

Through images and ideas the total number of objects in our experience is infinitely multiplied; for many of the things we have seen, or heard, or smelled, or tasted, we cannot again have present to the senses, and without this power we would never get them again. And besides this fact, it would be inconvenient to have to go and secure afresh each sensation or percept every time we need to use it in our thought. While habit, then, conserves our past experience on the physical side, the image and the idea do the same thing on the mental side.

3. INDIVIDUAL DIFFERENCES IN IMAGERY

Images to Be Viewed by Introspection.—The remainder of the description of images will be easier to understand, for each of you can know just what is meant in every case by appealing to your own mind. I beg of you not to think that I am presenting something new and strange, a curiosity connected with our thinking which has been discovered by scholars who have delved more deeply into the matter than we can hope to do. Every day—no, more than that, every hour and every moment—these images are flitting through our minds, forming a large part of our stream of consciousness. Let us see whether we can turn our attention within and discover some of our images in their flight. Let us introspect.

I know of no better way to proceed than that adopted by Francis Galton years ago, when he asked the English men of letters and science to think of their breakfast tables, and then describe the images which appeared. I am about to ask each one of you to do the same thing, but I want to warn you beforehand that the images will not be so vivid as the sensory experiences themselves. They will be much fainter and more vague, and less clear and definite; they will be fleeting, and must be caught on the wing. Often the image may fade entirely out, and the idea only be left.

The Varied Imagery Suggested by One's Dining Table.—Let each one now recall the dining table as you last left it, and then answer questions concerning it like the following:

Can I see clearly in my "mind's eye" the whole table as it stood spread before me? Can I see all parts of it equally clearly? Do I get the snowy white and gloss of the linen? The delicate coloring of the china, so that I can see where the pink shades off into the white? The graceful lines and curves of the dishes? The sheen of the silver? The brown of the toast? The yellow of the cream? The rich red and dark green of the bouquet of roses? The sparkle of the glassware?

Can I again hear the rattle of the dishes? The clink of the spoon against the cup? The moving up of the chairs? The chatter of the voices, each with its own peculiar pitch and quality? The twitter of a bird outside the window? The tinkle of a distant bell? The chirp of a neighborly cricket?

Can I taste clearly the milk? The coffee? The eggs? The bacon? The rolls? The butter? The jelly? The fruit? Can I get the appetizing odor of the coffee? Of the meat? The oranges and bananas? The perfume of the lilac bush outside the door? The perfume from a handkerchief newly treated to a spray of heliotrope?

Can I recall the touch of my fingers on the velvety peach? On the smooth skin of an apple? On the fretted glassware? The feel of the fresh linen? The contact of leather-covered or cane-seated chair? Of the freshly donned garment? Can I get clearly the temperature of the hot coffee in the mouth? Of the hot dish on the hand? Of the ice water? Of the grateful coolness of the breeze wafted in through the open window?

Can I feel again the strain of muscle and joint in passing the heavy dish? Can I feel the movement of the jaws in chewing the beefsteak? Of the throat and lips in talking? Of the chest and diaphragm in laughing? Of the muscles in sitting and rising? In hand and arm in using knife and fork and spoon? Can I get again the sensation of pain which accompanied biting on a tender tooth? From the shooting of a drop of acid from the rind of the orange into the eye? The chance ache in the head? The pleasant feeling connected with the exhilaration of a beautiful morning? The feeling of perfect health? The pleasure connected with partaking of a favorite food?

Power of Imagery Varies in Different People.—It is more than probable that some of you cannot get perfectly clear images in all these lines, certainly not with equal facility; for the imagery from any one sense varies greatly from person to person. A celebrated painter was able, after placing his subject in a chair and looking at him attentively for a few minutes, to dismiss the subject and paint a perfect likeness of him from the visual image which recurred to the artist every time he turned his eyes to the chair where the sitter had been placed. On the other hand, a young lady, a student in my psychology class, tells me that she is never able to recall the looks of her mother when she is absent, even if the separation has been only for a few moments. She can get an image of the form, with the color and cut of the dress, but never the features. One person may be able to recall a large part of a concert through his auditory imagery, and another almost none.

In general it may be said that the power, or at least the use, of imagery decreases with age. The writer has made a somewhat extensive study of the imagery of certain high-school students, college students, and specialists in psychology averaging middle age. Almost without exception it was found that clear and vivid images played a smaller part in the thinking of the older group than of the younger. More or less abstract ideas and concepts seemed to have taken the place of the concrete imagery of earlier years.

Imagery Types.—Although there is some difference in our ability to use imagery of different sensory types, probably there is less variation here than has been supposed. Earlier pedagogical works spoke of the visual type of mind, or the audile type, or the motor type, as if the possession of one kind of imagery necessarily rendered a person short in other types. Later studies have shown this view incorrect, however. The person who has good images of one type is likely to excel in all types, while one who is lacking in any one of the more important types will probably be found short in all.[4] Most of us probably make more use of visual and auditory than of other kinds of imagery, while olfactory and gustatory images seem to play a minor rÔle.

4. THE FUNCTION OF IMAGES

Binet says that the man who has not every type of imagery almost equally well developed is only the fraction of a man. While this no doubt puts the matter too strongly, yet images do play an important part in our thinking.

Images Supply Material for Imagination and Memory.—Imagery supplies the pictures from which imagination builds its structures. Given a rich supply of images from the various senses, and imagination has the material necessary to construct times and events long since past, or to fill the future with plans or experiences not yet reached. Lacking images, however, imagination is handicapped, and its meager products reveal in their barrenness and their lack of warmth and reality the poverty of material.

Much of our memory also takes the form of images. The face of a friend, the sound of a voice, or the touch of a hand may be recalled, not as a mere fact, but with almost the freshness and fidelity of a percept. That much of our memory goes on in the form of ideas instead of images is true. But memory is often both aided in its accuracy and rendered more vital and significant through the presence of abundant imagery.

Imagery in the Thought Processes.—Since logical thinking deals more with relations and meanings than with particular objects, images naturally play a smaller part in reasoning than in memory and imagination. Yet they have their place here as well. Students of geometry or trigonometry often have difficulty in understanding a theorem until they succeed in visualizing the surface or solid involved. Thinking in the field of astronomy, mechanics, and many other sciences is assisted at certain points by the ability to form clear and accurate images.

The Use of Imagery in Literature.—Facility in the use of imagery undoubtedly adds much to our enjoyment and appreciation of certain forms of literature. The great writers commonly use all types of images in their description and narration. If we are not able to employ the images they used, many of their most beautiful pictures are likely to be to us but so many words suggesting prosaic ideas.

Shakespeare, describing certain beautiful music, appeals to the sense of smell to make himself understood:

... it came o'er my ear like the sweet sound
That breathes upon a bank of violets,
Stealing and giving odor!

Lady Macbeth cries:

Here's the smell of the blood still:
All the perfumes of Arabia will not sweeten this little hand.

Milton has Eve say of her dream of the fatal apple:

... The pleasant sav'ry smell
So quickened appetite, that I, methought,
Could not but taste.

Likewise with the sense of touch:

... I take thy hand, this hand
As soft as dove's down, and as white as it.

Imagine a person devoid of delicate tactile imagery, with senseless finger tips and leaden footsteps, undertaking to interpret these exquisite lines:

Thus I set my printless feet
O'er the cowslip's velvet head,
That bends not as I tread.

Shakespeare thus appeals to the muscular imagery:

At last, a little shaking of mine arm
And thrice his head thus waving up and down,
He raised a sigh so piteous and profound
As it did seem to shatter all his bulk
And end his being.

Many passages like the following appeal to the temperature images:

Freeze, freeze, thou bitter sky,
Thou dost not bite so nigh
As benefits forgot!

To one whose auditory imagery is meager, the following lines will lose something of their beauty:

How sweet the moonlight sleeps upon this bank!
Here we will sit and let the sounds of music
Creep in our ears; soft stillness and the night
Become the touches of sweet harmony.

Note how much clear images will add to Browning's words:

Are there not two moments in the adventure of a diver—one when a beggar he prepares to plunge, and one, when a prince he rises with his pearl?