§ 2. The Motor Element in Ideal Revival. — Perceptual process is penetrated through and through by experiences of movement. Passive sensations only serve to guide and define motor activities. Besides the movements which directly subserve the attainment of practical ends, there are also constantly present the adjustments of the organs of sense involved in attending to percepts. There are the movements of exploration by which touch and sight follow the contours of objects. There are the attitudes of listening for sounds, and sniffing for smells, and the like. Ideal process, being a reproduction of perceptual, tends to reinstate the movements which form an essential part of it. In mentally reproducing the visual appearance of a thing we mentally follow the outline of it with the eye, and in general we tend to repeat in idea the movements of ocular adjustment. Similarly, in recalling a sound, we may mentally repeat the attitude of listening, or better still, mentally imitate the movements by which the sound is produced. If it is a sound which we are able more or less successfully to imitate by means of our own vocal organs, we mentally articulate it. Our power in this respect is greatest with the words of ordinary speech, so that when we recall them in the form of mental images, we constantly reproduce the motor process of articulation as well as the mere sound.

This revived motor element has a peculiar importance, because our power of freely controlling, detaining, modifying, and repeating mental images depends in a very large measure on our power of controlling their motor constituents or accompaniments. "The reason why revived movement is capable of discharging this special function is that our control over it is analogous and proportionate to our power of controlling actual movements."* "To show that this is so, we have only to point out that the more intimately a given experience is connected with motor processes peculiar to it and distinctive of it, the greater is our command over it in ideal representation." A good example is supplied by the articulate sounds of ordinary speech. "Let any one select for mental experimentation any word or sentence; he will find that he has almost as great a control over the internal articulation as over the external. The chief restriction appears to lie in the inability to make the represented sound as loud as the actual sensation; but, apart from this, one may do almost what one likes with it. We may repeat it thousands of times with unfailing definiteness, precision, and certainty; we may say it rapidly or slowly, with emphasis or without emphasis or with emphasis that varies; we may even invert the order of the sound with as much freedom as in actual utterance. The same holds good with the simpler geometrical figures. We can trace them mentally much as we trace them physically."* Contrast such cases as that of smells, or of organic sensations. Many persons can mentally reproduce odours with great vividness and accuracy; but vivid and accurate reproduction is one thing, and free control is another. We cannot, as in the case of articulate words, pass from one odour to another in a series, with greater or less rapidity, varying the order of succession according to our caprice or convenience. We cannot repeat the same odour "thousands of times with unfailing definiteness, precision, and certainty"; we cannot vary its intensity at will as we can the loudness of articulate sounds. So far as we have any power in this respect, it appears to be indirect and depends on the recall of the appearance of odorous objects or of other associative circumstances. We cannot simply take some smell, and in idea freely run up and down the scale of its varying intensities; according to all analogy, we should be able to do this, if we possessed and habitually exercised the power of actually producing the smell, and varying its intensity by our own movements.

It is in the motor elements of the mental image, and in the control which they yield over the image as a whole, that we have ultimately to look for the origin of expressive signs, or in other words, of language, in the broadest sense of the term. We have said that language is an appropriate means of fixing attention on ideally represented objects, as distinguished from perceived objects. Since the means of controlling ideal representations lies in the motor constituents of mental images, the source of language must be found here or nowhere. The first definite stage in the development of expressive signs is constituted by the tendency of ideas in so far as they have a motor aspect to issue in actual movements.