# The Foundations of Normal and Abnormal Psychology/Part 2/XIX

Representative elements form what may be characterized as mental trains. The elements of a mental train are connected by relations of contiguity, resemblance, and contrast. Association by contiguity depends on the frequency, recency with which the elements have been associated, while resemblance and contrast may be regarded as two or more mental trains of representative elements associated by contiguity, crossing and intersecting in a few points, in other words having some element in common. From this standpoint associations by resemblance and contrast are often regarded as cases of contiguity which is therefore considered as the mode of association characteristic of representative elements. From another standpoint, however, resemblance may equally be considered as fundamental. It is nearer to the truth to regard both contiguity and resemblance or similarity as fundamental modes of association of representative elements.
Association by contiguity may be expressed in the following general proposition: Ideas or images which have frequently followed one another tend to recur in the same order. If a, b, c, d, e be images or ideas that have frequently followed each other in a definite order of succession, then the tendency is that the ideas or images will occur in the same order, if the initial idea or image is awakened. Thus if a, b, c, d, e be that order, then if a is to awaken the rest, b, c, d, e, tend to emerge in the same order in which they have followed each other previously.
The formula for association by contiguity may be expressed as follows: a+b+c+d+e+. . . .
Representative elements, however, as we have pointed out are derivative, they are functions of sensory compounds, and vary concomitantly with the wealth and differentiation of sensory life-experience. Blind people have no visual images, nor can deaf persons form any idea of a sound. Although representative elements are essentially different in nature from sensory elements and their compounds, still it remains true that sensory experience is the soil from which the rich variety of representative life grows up. Sensory elements and their compounds are prerequisites of representations of their combination and organization.
The course of associative relations of representations may be determined by the course of sensory series. If a series of sensations and perceptions have frequently followed each other pretty uniformly, then their corresponding representations will tend to recur in the same uniform order. Let A, B, C, D, E . . . .be the order of succession of the sensory series, then the order of the series of representations will be: a, b, c, d, e . . . . When sensation A with its corresponding representation a are awakened, or if a alone occurs, then the rest of the series of representations tend to emerge. The formula for association of contiguity may be somewhat modified and represented as follows:
A+a+(b+c+d+e), or simply a+(b+c+d+e). . . . B+b+(c+d+e), or simply b+(c+d+e) . . . .
We have shown that ideas and images are associated with motor and physical reactions, hence muscular movements or rather kinaesthetic sensations and their representations also enter the circle of the associative series. The series of representations gives rise to movements which in their turn give rise to kinaesthetic sensations, and these in turn may either give rise to another series of representations, or may maintain the same series. Hartley, the father of English associationism, who reduced all association to contiguity, states his doctrine of association in the following general proposition:
"If any sensation A, idea B or muscular motion C, be associated for a sufficient number of times with any other sensation D, idea E, or muscular motion F, it will at last excite d, the simple idea belonging to the sensation D, the very idea E or the very muscular motion F."
Turning now to association by similarity we find that the relations of the elements are somewhat more complex than in that of contiguity. Where mental life is complex and where there are present many different trains of ideas and images, there will be a tendency for them to cross and intersect at many points. The course of a given train of ideas and images instead of running in its habitual line will tend to become deflected along other lines and give rise to that particular form of association of representative elements known as association by similarity and contrasts.
Let a, b, c, d, e, f, be one series and let p, b, g, r, m, another series, q, r, k, l, n, a third series and s, l, x, y, z a fourth series and so on. The course of association instead of running along one line of habitual association determined by contiguity will tend to run on new lines. The course may be represented as follows:
Let each series be represented by a row of squares formed into a rectangle and let each crossing series be represented by a similar rectangle intersecting the preceding one at right angles, then the course of association by similarity may be diagrammatically represented as follows:
The course of the mental train of ideas is changed and deflected along lines which are otherwise unhabitual for the particular mental train. In association by similarity the mental train ever coruscates along new-lines.
Association by similarity may be expressed in the general proposition: like states often follow each other. What that likeness consists in we have already seen,―it is some common characters, some representative elements which two or more crossing trains of contiguous representations possess in common. The crossing of one train by another at a point where the representations have common features is purely accidental, as far as the crossed train is concerned; it is the play of the imagination. As an illustration of such a crossing of trains we may take the example when one, from a series of images and ideas about the recent Americo-Spanish war, is led to think of the Anglo-Spanish war in the 16th Century, the common representation being the destruction of the Spanish fleet; and from the mental train on the Anglo-Spanish war to the Franco-Prussian war the common representation being invasion, and from this to the Napoleonic war, then to the political affairs of France, and thence, to the peace conference of European powers. The course of the trains of ideas is every time deflected along new channels. The deflection depends largely on the complexity and number of the trains and their activity.
The relation of likeness is present not only in trains of representations, but also in presentations or in what is termed by us psychic compounds. Thus twins we say look alike, so do eggs, so do animals of the same species; a picture say of a landscape looks like the actual landscape, and a portrait or statue resembles the original. In all these examples the likeness is constituted by the sensory elements common to the presented psychic compound. Not that the sensory elements are exactly the same, subjectively considered, they may be totally different in their psychic stuff, in the psychic relations that cluster about them, as no two sensations, no two psychic compounds, are really the same, as far as the mental state is concerned, but they refer to the same characters in the external object. It is this common reference to the same traits or characters in the external object that constitutes the bond of association of likeness in sensory element or psychic compound. On the same grounds may be explained the likeness between the representations and the psychic compound, the percept, which it represents.