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Presentations.

Psychology must begin, then, by describing observed appearances (the literal translation of the word 'phenomena') without any prejudging of the issue as to what is the cause of these. So, though it may speak of such phenomena as if they were things, it must not be regarded as asserting that they are, at bottom, anything more than effects associated with brain-workings. It leaves, at the outset, that question open.

Field of Presentation.

All such phenomena it styles 'Presentations', and it regards them as located within the individual's private 'Field of Presentation'. (We shall employ this term in preference to the commoner 'Field of Consciousness', which is insufficiently definite.) This field of presentation contains, at any given instant of Time, all the phenomena which happen to be offered for possible observation. Let us take a concrete example of what that means. You are now reading this book, and your field of presentation contains the visual phenomena connected with the printed letters of the word you are regarding. It contains also, at the same instant, the visual phenomenon pertaining to the little numeral at the bottom of the page. This you 'failed to notice'; but the numeral in question was, clearly, inside the area covered by your vision—it was affecting your brain via the eye, its psychical 'correlate' was being offered to your attention. And that statement holds good for a host of other visual phenomena. On reflection, you will also agree that the field must have then contained—presented to attention but left 'unnoticed'—certain muscular sensations such as pressures against your body, quite a number of sounds, and the pleasant feeling produced by the air flowing into your lungs as you breathed.

Attention.

It would be unsafe to say that these comparatively unnoticed phenomena were not being consciously observed. When you are watching a fall of snow, observation may be concentrated upon a single floating flake; but that does not mean that you fail to perceive the remainder. Were these to vanish, leaving the single flake in the air, their disappearance would instantly distract your startled attention from the object of your previous pre-occupation. When listening to the playing of an orchestra, you do not need to cease following the music in order to be aware that the irritating person in the seat ahead has stopped beating time with his programme. As a general rule, however, observation seems to be definitely centred upon one or another specific part of the crowd of presentations—though we have no psychical evidence to show that this is anything more than a matter of habit. Observation thus centred is called 'Attention'. It is usual to speak of the part of the field centred upon as being in the 'Focus of Attention'; and it is a matter of common knowledge that, at and around this 'focus', attention may be concentrated in greater or less degree of intensity.^[1]

In Physiology (the science which deals with the brain as a physical organism) the field of presentation would be merely the particular part of the cerebrum which happens to be, at that moment, in the state of activity associated with the production of psychical phenomena. And the focus of attention would be simply that particular brain path which the maximum current of nervous energy happened to be following. One would be apt to suppose, off-hand, that this maximum flow would be produced by whatever happened to be the greatest sensory stimulation; but such could not be the rule. The hungry man, coming to the luncheon table, has his attention focussed, not upon the brightness of the shining silver, but upon the far duller sensory stimulation of the well-browned mutton chop. Attention, therefore, may be either attracted from without the organism or directed from within. If we were to attribute such directing to the ultimate observer, we should be admitting him to the status of a full-blown 'animus' with powers of intervention. For, as every schoolboy knows, the concentrating of attention has a very marked effect in the formation of memories. But the physiologist would argue that we have no right to regard this internal directing of attention as originating in anything beyond the purely mechanical internal condition of the brain.

Now, the field of presentation at any given moment may contain a great many observable phenomena besides those sensory appearances which we have been considering. It may contain, for example, 'Memory Images'.

What sort of a phenomenon is a 'memory image'?

Impressions.

Presentations may be divided into two sharply differing classes. The first of these comprises all phenomena which appear to the observer as directly attributable to the action of his outer sensory organs or nerve endings. That they are truly associated with the activities of such surface machinery is evident from the fact that movement of, or external interference with, the organs or nerve endings in question results in an alteration of the character of the phenomena observed, and from the equally significant fact that, in the absence of such movements or interferences, the phenomena remain unaltered and unescapable. They cannot, in popular parlance, be 'willed away'. Such phenomena are styled 'Impressions'.

Images.

But now, picture to yourself a room which you remember. There is no doubt that what you are observing is a visual presentation—a mental picture. The process is not one of saying to yourself: 'Let me see: there was a sofa in that corner, and a piano in the other, and the colour of the carpet was such-and-such.' Rather does the whole of what you remember come before your eyes in the form of a simultaneous vision. If, however, you want to make absolutely certain that such visual pictures are not things which you deliberately manufacture from a catalogue of verbally remembered detail, you may try the following experiment. Look carefully at a painting of a landscape; then, after half an hour, try to re-visualize what you saw. You will find that you can re-observe much of the exact colouring of the original impressions—the peculiar olives and browns and greys—even though many of these colours were quite beyond your powers of artistic analysis, let alone verbal description. So you must be observing, as an 'image', an arrangement of colours similar to those which you saw as impressions.

Reality Tone.

There is a difference between an impression and its related image which it has puzzled every psychologist to describe. It lies in the presence or absence of what is sometimes called 'sensory vividness', but what, I think, would be better referred to as 'Reality Tone'. As compared with a room which you can see with your eyes, the room you are remembering seems unreal, yet real enough to be recognizable as a visual, and not, say, an aural image. Again, strike the rim of a wine glass, and listen to the sound as it dies away. It grows fainter and fainter till it vanishes; but to the last (as Ward points out) it retains its reality tone. After it has entirely disappeared, you can remember what it sounded like just before it died away. That memory is recognizable as a memory of sound—an aural image. It has all the tonal qualities of the original faint impression; but it lacks the appearance of reality.

Again, compare the true memory image with the phenomenon commonly called an 'after-impression'. The latter may be easily observed. If you stare hard for sixty seconds at a brilliant red lampshade, and then look up at the ceiling, you will see, after a moment or so, a patch of green, shaped in outline like the lampshade. This phenomenon is dim, exhibits little, if any, detail within its boundaries, is of the opposite (complementary) colour to the original impression, and lacks all perspective—seeming to be flat all over. It possesses, however, reality tone, and is clearly an impression. It moves as you move your eyes. But, while actually watching this green patch floating before you, you can observe a true memory image of the original impression of the lampshade. It is of the original red colour, exhibits much internal detail, and appears to be three-dimensional—i.e., to possess the depth apparent to binocular vision.

Five minutes later, when all trace of the green after-impression has vanished, you can observe at will clear memory images of either red lampshade or green patch.

It may be noted, then, that images are phenomena quite distinct from mere fading impressions.

[1]

The reader should distinguish between the focussing of attention and the performing of body movements to assist observation. With his eyes focussed upon a dull object before him, he can focus attention upon a brighter object in his field of vision. And he can, subsequently, shift the focus of vision to the brighter object.