125. What kinds of mental states are called perceptions?
126. Illustrate the change of a percept into a mental state not worthy of the name, caused by a change of the situation which involves neither a subtraction nor an addition of stimuli.
127. What impressions become a part of the percept, and what impressions do not?
128. Show that a percept contains not only less, but also more than the sensations corresponding to the stimuli of the moment.
129. What can we learn about perception from the drawings of children?
130. Illustrate the perception of a thing whose parts appear spatially separate. (None of the illustrations in the text strictly answers this question.)
131. What changes occur when a rabbit’s head is perceived as a duck’s head?
132. Are illusions signs of mental abnormality? What are they?
133. What two classes of illusions are distinguished in the text?
§ 15. IDEATION
The same laws which govern the supplementing of impressions by images, govern also the supplementing of images by other images. We refer to the appearance of images supplementing other images by the word _remembering_, or _ideation_.
What we remember is always deficient in details compared with what we perceive. Remember a landscape, a street scene, a well-known person. Innumerable details are always lacking in the idea, although they were present in the corresponding percept. These details which are lacking may be either parts separable from the object, or mere attributes of sensation inseparable from the sensation. On the other hand, ideas are richer than percepts. They contain elements obtained from other similar perceptions and added by association, as when the idea of a landscape is enriched by a tower, the idea of a person by a beard, which actually are not present at these places.
Ideas are also strongly influenced and altered by other ideas which happen to be in consciousness at the same time (“set of the mind”); for instance by questions, particularly by questions in the negative form--“did you not,” “was this not,”--by the wish to make a good impression upon others, and by similar factors. We may have no intention of exaggerating, in Falstaff’s fashion, the significance of our deeds; nevertheless our memories become gradually modified so that the uncommon, the important, the valuable in them is emphasized, and the common, the insignificant, the unpleasant is obliterated. Wherever our memories are fragmentary and indefinite, they offer but slight resistance to questions attacking this point, for instance: Do you believe that the gentleman was as tall as you are?
Memories are thus, not exceptionally, but universally inaccurate representations of that which has been perceived. This has recently been proved by direct experimental tests. Since percepts, although they rest on a foundation of external stimulation, are so strongly influenced by the mind’s own manner of functioning, the existence of this influence in the case of imagery, lacking such a foundation, is not surprising. Although memories are but rarely totally misleading, mankind has long ago learned to rely upon memory in all important business and legal transactions only when there is agreement between the memories of several witnesses. The changeableness of memory is particularly strong in the child’s mind. The perceptual experiences have not been so often repeated as in the adult mind, and the practical importance of accuracy of remembering has not made itself so much felt. For both reasons the child’s memory is very unreliable.
The word _imagination_ is frequently used to signify a specially strong ability to modify memories by associated images. Thus we speak of the imagination of the child--but also of the artist and the scientist. Without imagination the scientist would not succeed in his task of making the phenomena of nature more comprehensible by showing the consequences of the remotest relations between things. It is clear, however, that imagination is not a fundamental “faculty” of the mind, separable from other “faculties,” but a result of the fundamental laws governing mental functions.
Let us turn to the fragmentary nature of reproduced experience and discuss its significance. That previous experience can be reproduced only in fragments is the direct result of the selective power of attention, which asserts itself in both perception and ideation. Not every quality of a thing presented is equally interesting. A child having a watch takes interest mainly in the ticking and in the glitter of the golden case. Meeting a dog, he gives attention to the terrifying bark and the multiplicity of legs. Suppose now that the dog regularly occurred together with a special impression, perhaps a spoken word; then the recurring of this symbol will tend to reproduce in the child’s mind the image of the dog. But the pressure of many competing tendencies does not permit the reproduction of all the qualities of the dog which have become conscious on former meetings with this animal. Only an extract, so to speak, of these qualities is reproduced, and this is made up of those which were formerly especially interesting,--the bark and the legs.
Another factor determining the selection of special qualities of a thing for reproduction is the frequency with which each quality reappears in things which are different in certain respects, but in other respects belong to the same class. The trees of a forest beside which I am walking have many individual differences. But certain features are common to all the trees. These common features reappear again and again, while each of the other features appears only now and then. The same can be said of various dogs met on the street, of various tones of a violin, and so on. If the perception of the trees is experienced together with a certain other percept which may serve as a symbol for the trees, for example the word _tree_, the association of the symbol with those regularly repeated qualities becomes firmly established, whereas the association with the other, more or less varying qualities, remains comparatively feeble. The result is that the symbol tends to reproduce almost exclusively the former qualities. These come to make up a separate group of images, a general idea.
The laws of attention, practice, and memory, together with the simple uniformity of nature just mentioned, produce thus a peculiar result. They remove ideation from the accidents of external events in an incomparably higher degree than perception. They bring about ideas of the separate qualities of the things perceived, _abstractions_, and ideas of common features, _general ideas_. In many cases an idea is both an abstraction and a general idea. Examples of such ideas to which no equally simple concrete object corresponds, are the idea of a mere length, the color red, sight, a dog in general, a tree in general.
These ideas are of eminent importance for all higher mental development. Mind, in them, departs from that which nature presents, but only in order to take possession of it more securely by systematization and by overcoming the narrow limits of the capacity of consciousness.
By separating the common qualities of things from those which vary we classify the things into kinds and species, we think of them as being in various ways related. Instead of having an incomprehensible mass of things standing side by side, we have a system of coördinated and subordinated things, of groups formed according to closer or remoter relationship; and thus it becomes a comparatively easy matter to survey the multitude of things of which nature consists. Not only order, but law too is thus brought into the phenomena of nature. If we collect sticks of wood and set fire to the pile, we notice that some of them burn lustily, others smolder and smoke, still others do not burn at all. Why so? Repetition of similar experiences is necessary before we can give an answer; but mere repetition of the same event does not enable us to give the answer. The event must be broken up and general ideas must be formed out of the elements of the event. Then only can we answer the question. Some of the sticks burn because they are dry. Others do not burn so well or do not burn at all because they are wet. Neither shape nor color nor origin nor many other qualities of the sticks have any causal connection with the difference of burning and not burning. Both order and law in nature are recognized by abstraction.
Equally important is the overcoming of the narrowness of consciousness by abstraction and generalization. When I am thinking of trees, the contents of my mind are very few. There may be a word image, a visual image of something tall and branching; hardly more. All the special features of trees of all kinds are absent from consciousness. So I can easily think of additional things, for instance of the age which trees may reach, or the elevation at which trees cease to grow. But the moment I begin by accident to think of a thing which does not harmonize with those features of the tree which thus far have been absent from consciousness, immediately those features become conscious and inhibit the contradictory thoughts. They have been unconscious and yet we cannot say that they have been sheer nothing. The consciousness of the general idea has in some way prepared the path for the special features from which it has been abstracted. They have been carried close to the door of consciousness, so to speak, and the slightest impulse coming from an associated idea will cause them to enter. This is our meaning when we say that within the general idea of which we are conscious all those special features are included. They are included by representation, the general idea being the deputy taking care of their interests. Thus our mind is freed from the necessity of carrying at any moment a heavy load of actual states of consciousness and is nevertheless able to act as reasonably as if those mental states were present. In using representative ideas, our mind has actually at its service the enormous number of all those individual ideas which are represented by them.
