Law of Contiguity.—The principle of association by proximity is not confined to ideas.• We must state it in a more comprehensive form, in order to comprise the full sphere of its application; for our mechanical habits are formed through the very same power of our constitution that enables us to recall or remember ideas. The taught movements of a soldier or of a skilled workman are connected together so firmly that One succeeds to another almost of its own accord. Everything of the nature of acquisi tion supposes a plastic property in the human system, giving permanent coherence to acts that have been performed together.
The following is a general statement of the law under consideration: Actions, sensations, states of feeling, and ideas, occurring together, or in close succession, tend to grow together, or cohere in such a way that when any one of them is afterwards pre sented to the mind, the others are apt to arise.
And first, as to association of actions, or voluntary movements. When we perform a train of movements without any further aid of the will than to commence the series, there must be a fixed connection between each and the one that follows, and tliis con nection may be either instinctive or acquired. There are various cases of instinctive trains, such as the action of the heart. lungs, and intestines, and the movements of deglutition. When a morsel of food reaches the back part of the mouth, the muscles of the throat seize hold of it, and transmit it to the stomach, independent of our will. The connected movements in this case are provided for in the original structure of the nervous and muscular system. In walking, there is partly an instinctive tendency to alternate the limbs, and partly a confirming acquisition, the result of practice. But in those complicated operations that human beings arc taught to execute in the various avocations of life, the associating principle is everything. The apparently simple and easy act of taking food is a complicated acquisition; in other words, an extensive group of associated movements. The seizing of the morsel is followed by the movement of the arm that carries it to the mouth; the mouth is opened simultaneously; after which follow the processes of biting and chewing; all which take place with the certainty of a machine, and without effort or attention directed to them. These associations were originally built up by slow degrees. " As a general rule, it takes many repetitions to cement so firm a union between successive and simultaneous movements as is implied in the above instance." A good example of the association of movements is furnished in our requirement of spoken language, as in committing to memory words, sayings, and passages of books. When a child has perfectly acquired the Lord's prayer, the chain of association is so firmly knit, that the articulation of the words "Our Father" is followed irresistibly with those next succeeding, and so on to the end. The cohesion in this case is between
the vocal movements corresponding to the enunciation of the words. Having gone many times through this one definite succession, the stream of nervous power, in some way that we cannot at present explain, acquires a tendency to fall into this one definite track, and in future to bring on the movements in the exact order that they have so fre quently followed.
It is not merely actual movements that can be joined together in this way, but the ideas of movement; for a man, meditating in language, and not speaking out hit thoughts, can consolidate his trains so as to remember them afterwards.
When we proceed to sensations and the ideas, or subsequent traces, of sensations, and take along with these the variety of our movements with their ideas, we finch an unlim ited scope for the associating principle; and the consequences of its operation spread far and wide in the domains of our happiness, our knowledge, and our active capacity. It is only possible here to present a few illustrative examples.
In the various mechanical acquirements, which include the whole of special handi craft, industry, and skill, as well as the use of the bodily members in the more general actions of daily life, there may be traced the linkings of actions with actions, or actions with sensations and ideas. The helmsman steering a ship associates in his mind each deviation of the needle from the proper point with the specific muscular exertion to be applihd to the wheel to rectify the ship's direction. The workman fabricating in wood, metal, or stone, acquires a firm connection between each aspect of the material and the muscular power to be applied to bring it one step nearer the desired form. The power of copying anything we see, as in writing, drawing, molding, etc., when completely Mastered, is made up of associations between a visible appearance and the train of movements calculated to reproduce it. After practice, all this it done, as it is called, mechanically, or without those operations of considering, willing, and remembering di rections, that are essential to the learner in a new art. The associations that grow up after a certain amount of practice, are in this case associations between movements and appearances to the eye, or sensations of sight. In the greater number of crafts, the eye is the guiding sense to the operator, but not in all. Sometimes the effect is vocal, as in performing music, and in making and tuning musical instruments, in speaking, etc. In other arts, the touch is the guiding sense, and in some, as in cookery, the taste and smell direct the operator. Each accomplished workman has in his mind many hun dreds, not to say thousands, of couples or aggregates of definite movements with other movements and with sensations, contracted in the course of his apprenticeship to his calling.