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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
( 131) reacted to as a whole, and because every one of the movements involved in attending to its parts is associated with the movement of reacting to the whole object. Some of these movements which are associated with various parts or aspects of an object are compatible: the fact that they lead to the common outlet of a movement made to the whole object may thus transform them into simultaneous systems. Others are incompatible, and must be united in successive rather than simultaneous systems; thus, for instance, one cannot attend simultaneously to both ends of a pen, but the whole object is a unity because of the possibility of responding to the whole of it by a single movement or movement system. Of the motor responses thus linked together by their common outlet, the compatible ones become simultaneous systems, relating to those parts of the object that can be attended to together; while the incompatible ones become successive systems, either reversible or irreversible, relating to those parts of the object which must be attended to in succession.
On a non-motor theory of association, which would make the formation of an associative disposition result from a lowering of resistances at the synapses on a pathway directly connecting two sensory centres, and resulting from their simultaneous activity, it is commonly held that all associations are based on simultaneous rather than on successive experience. Thus Offner (98) says that when two successively occurring impressions are associated, it is because the second impression is simultaneous with the memory after-image or perseverative process of the first. Wohlgemuth (154) has recently maintained on the basis of experimental results that all association is between simultaneously occurring experiences. He required his observers to form an association between a color and a form (a) when the form was colored; (b) when a black shape was shown on a colored ground; (c) when a colored field was shown alongside of a black shape on a white ground; (d) when a colored field was shown followed by a black shape on a white ground, or vice versa. It was found that "the more the members of a group
( 132) are apperceived as a whole, the stronger their association with each other," and from this it is concluded that " all associations are due to simultaneity." It is evident that the superiority of the associations in impressions that were apperceived as a whole, for instance, of the association between color and shape when the shape is itself colored, is due to the fact that besides the simultaneous responses made to the two factors of color and shape, there is a single response to the whole impression; thus the simultaneous impression has the great aid of a single unifying motor reaction.
Just as the unity of the perception of an object depends on the possibility of making a single movement or movement system in response to the object as a whole, so of course the possibility of reviving a memory image of an object as a whole depends on such a single response. Upon the strength of the simultaneous and successive systems thus linked together by their common outlet will depend the completeness and accuracy with which a memory image can be analyzed into details corresponding with the original. It is not necessary to emphasize the importance of a word or name as furnishing a convenient unifying response to the whole object. One cause of the low stage of intellectual development of animals is the very limited extent to which they can hold together the parts of their experience by making reactions to a whole group of such parts as a single group. Beasts that, like the monkey, the elephant, and the raccoon, have grasping organs with which to move things about have a great advantage so far as the formation of perceptions of objects is concerned. But the unrivalled instrument of unifying motor responses is of course language. By its help we can not only hold together into a system our responses to the various aspects of a single concrete object, but we can in a similar way form systems out of the aspects or features which a number of objects have in common. We can form those systems which are the bases of general ideas or concepts, such as the concept dog or animal. There is almost no limit to the complexity of the system combinations which