IMAGE, Psychological. The term as em ployed in psychology has two different mean ings. Traditionally, the image is a copy or representation of a former perception, or a compound of such representations, as for ex ample, the picture we see when with closed eyes we recall or imagine some object. Such an image, however, is complex, and by analysis it reduces to a number of simple images which synthetically combine to form an idea just as a number of sensations combine to form a per ception. A more careful terminology, there fore, would regard the image as simple and would define it as tan elementary mental process, akin to sensation and perhaps indis tinguishable from it, which persists when the sensory stimulus is withdrawn or appears when the sensory stimulus is absent?' (Titchener). Notwithstanding the greater accuracy of this second definition we shall (since we are in terested primarily in the general nature of imaginal experience), employ the term in its common rather than in its technical sense. We shall, therefore, take the image to mean the conscious representation of former experience.
It is a moot question whether the image differs psychologically from sensation. Some psychologists believe that the image is more filmy and faded out than sensation, and that its intensity and duration are character istically less. But to this it is replied that these are differences in degree, and not in kind; that sensations themselves show these differences. The only certain distinction, therefore, is logical rather than psychological; we say that we have a sensation when the stimulus is present and an image when the stim ulus is absent. In everyday life, of course, there are still other cues which are taken by the individual to mark off sensory from imaginal experience; images are frequently less distinct, they are of shorter total dura tion, they fluctuate, they fade out and dis appear, they do not belong to the situation in which at the moment we find ourselves, etc., but all these when taken as cues are mean ings which we put upon the bare experience, and, therefore, we often find that we are wrong, that the experiences which we take to be perceptual are, after all, imaginal.
If, however, we compare different kinds of image, then we find some that are clearly more like sensations than others. One group contains images which are conditioned upon recent stimulation of the sense-organ. The positive after-image which has the same quality as the sensation which precedes it, the negative after image which always appears in an antagonistic quality, and the memory after-image which is similar to the positive but has other conditions — all three occur upon the cessation of the stimulus, and are undoubtedly sensory in character.
There are others, which we may call con comitant images because they fill out or occur concomitantly with perception, that are not so obviously sensory as those in the first group. The memory color image by means of which we always see an object in the same color quality that is familiar to us in daylight; the image* which, for example, appears in mutilated letters or outline drawings as gray lines or patches of color, and thus fills out the lacuna in the perception; and finally the image of synwsthesia, the best known example of which is colored hearing (sound accompanied by color)— all of these have the marks of sensory experience as regards their relative stability, uniformity of occurrence in the same individual, and their concomitance with other sensory experience; but, on the other hand, they appear also to be conditioned upon associ ative tendencies in the brain, i.e., we see ob jests according as they mean, or, as in synmsthesia, there is prolably some abnormality among the associative fibres. Images in this group are, therefore, peripheral in character but centrally initiated.
There remain still other images which are dependent neither upon recent stimulation, nor upon concomitant perception but only upon associative tendencies. There are two kinds of these ((free images,* the image of memory and the image of imagination. So long as the images are simple, psychology is unable to dis tinguish them, but in the complex form they are accompanied either by the feeling of familiarity or by the feeling of strangeness. In the former case the idea comes to us as consciously familiar, and we call it the image of memory; in the latter the idea comes to us as new, and we designate it the image of imagination. When once we have learned to ize them, however, we find that their are not the same. The image of memory, for instance, is subject to change in the course of time—it may fade out, it may approximate to a type, or it may be in corporated into a new complex of which is imaginal. The image of imagination, on the other hand, is more stable, it may maintain both form and quality for a long time and then it dies away. Furthermore, an image of memory may appear in different modes with out change of meaning, e.g., a series of • non sense syllables may be learned visually and recalled verbally, whereas the image of imagi nation cannot be replaced by imagery from another sense department.