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Chapter 7: Simultaneous Movement Systems
Margaret Floy Washburn
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A SIMULTANEOUS movement system is one where the movements, instead of being dependent each on the one which preceded it in time, are mutually interdependent and occur together. The linking by associative dispositions takes place in both directions. or in all directions if the system is composed of more than two movements. Not only are the kinaesthetic excitations produced by the movement A the necessary stimulus to movement B, but the excitations resulting from B are the stimulus to movement A. It is evident that in such systems the component movements must be compatible. They must be of such a nature that they can be performed at the same time. Thus two articulatory movements could not enter into a simultaneous movement system: you cannot pronounce t and b at the same moment. But the movements involved in pronouncing a word and those involved in looking at the word printed, or calling up a mental image of its appearance, are compatible, and could enter into a simultaneous system. In our perceptions of objects, some of the movements are compatible and enter into simultaneous systems, while others do not.
An originally simultaneous system is formed by the actual occurrence of the movements together, and strengthened by each repetition of their synchronous occurrence. Meyer (83), in 1910, following a method suggested by Ach, tried to bring about the formation of simultaneous systems under experimental conditions. The observer was shown a series of cards, each card carrying two groups of simple figures, and each shown for the very short instant of 135 thousandths of a second: the interval between each card and the next was the same very brief time. In the test, the observer was shown one half of the card and required to draw from memory the figures that were
( 129) on the missing half. The brief exposure was intended to keep the observer from attending successively to the two halves of the card, and force him to attend to them simultaneously. The short interval between exposures would, it was thought, in a similar way keep him from attending successively to the two parts of the memory after-image of the card. Learning and correct recall proved to be possible by this method. It is evident that only those parts of the card could really be simultaneously attended to which did not involve incompatible movements. It is also evident that most of the learning which we do in ordinary life is performed under conditions very different from these.
Where the movements which enter into the system are very simple, they may form themselves into simultaneous systems, probably, by actually occurring together. But in all the concrete examples one can think of where simultaneous systems are formed, one comes to do the two things together, or attend to them together, through a preliminary process of attending to them alternately. The leg and arm movements of a practiced swimmer form a simultaneous system, but in learning to swim they are performed alternately, and even after one really begins to swim one has difficulty in not attending to them alternately. The static movement system of holding the head perfectly still and the phasic system of the arm swing are formed into a simultaneous system when one learns to make a golf stroke, but their simultaneous performance is possible only by having attended to them alternately as a beginner. When one has perfectly learned a language, the sight of a word and its meaning are simultaneous; but in the beginning one attended alternately to the printed word and the idea of its meaning. When associative dispositions leading in both directions are formed between two movements, so that either one can excite the other successively, if they are compatible movements the tendency is apparently always for them to form simultaneous systems. The greatest aid to the formation of simultaneous systems is the association of each of the two movements with
(130) a common third. If C and B are compatible movements, and associative dispositions have been formed between A and C and between A and B, then when A occurs, there is a tendency for B and C to be simultaneously excited. Thus Miller and Pilzecker (90 found that if a syllable such as 'bez' were learned at one time in connection with the syllable 'gaf,' and at another time with the syllable 'jip,' when 'bez' was later given the observer might respond with a kind of hybrid like 'gap.' Both of the former associates of 'bez' were reproduced, but the incompatible movements were forced out and a compromise was reached in the combination of elements from both syllables. This method of forming simultaneous systems by linking each of several movements to a common motor response is of the utmost importance for our experience. It is precisely thus that those simultaneous movement systems are formed on which are based what we call perceptions of objects, as well as ideas of concrete objects and of abstractions.
The perception of an object consists of a number of sensations, some of which are peripherally excited, that is, caused by the activity of our sense organs at the moment, while others are centrally excited, that is, the revival of former sense experiences. A piece of ice looks smooth, white, hard, and cold: we realize that only the whiteness of it is the result of present sense stimulation, and that the hardness, smoothness, and coldness are the effects of former experiences with the senses of touch and temperature. Now the way in which we form such combinations of sensations into perceptions is evidently not so much by adding bit to bit to form a mosaic, as by digging one bit after another out of an original whole. In first making acquaintance with an object we respond to it as an undifferentiated whole: later we come to make specialized responses to various parts and aspects of it; but it is the fact that it can be still responded to as a whole that keeps these specialized movements together in a single system, and thus gives the object its unity. An orange, or a chair, or a tree, is a single object, and not a mere aggregate of qualities and parts, because it can be