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the last rubric he gives the often quoted descriptions of the muscular mechanism of attention directed outwards toward external objects, and of attention directed inwards toward internal objects.1 Ribot finds his greatest difficulty in the application of the motor theory when he enters upon the consideration of attention to abstract ideas and concepts. He admits that the motor elements here are very feeble, but adds that "this is in accordance with the experience that abstract reflection is impossible for many, difficult and fatiguing for almost everyone." He finally explains the difficulty by maintaining that abstract thought deals only with words. A motor element is found in our word ideas, though its form varies somewhat according as the individual is more or less of the motor, visual or auditory type, 3
It seems unnecessary to give any further summary of a theory so generally known as Ribot's. Before we review any other theory, however, there are three criticisms to be passed on Ribot's discussion of the attention as essentially motor. (1) He assumes that the alternative to his own theory is a denial that there is any essential connection between muscular manifestations and attention. The crucial test would consist in seeing whether a man deprived of all power of external and internal motion, and of that alone, would still be capable of attention. The case is one that can not be realized."5 But the motor phenomena may be regarded as the inseparable concomitants of attention and yet not as its constitutive elements." They may be only one class among several of the conditions of attention. This is Külpe's view of their significance. Or they may be fundamentally related by the constitution of the nervous system to other processes that have a better claim to the name of attention. This accords with Bastian's view of attention as essentially sensory, yet inseparably bound up with motor activity." No theory denies that the muscles have an important part to play in the process of attention. (2) Ribot does not give any materials for the resolution of a difficulty that presents itself after a moment's reflection upon his explanation of at
Pp. 27, 28.
Op. cit., p. 86.
E. g., p. 84.
Ribot's treatment of the dependence of attention on affective states, and his definition of attention as an "intellectual mono-ideism," need not concern us here. Whatever may be the logical outcome of either position, neither is so developed by Ribot himself as to modify his conception of attention as essentially motor. Op. cit., p. 88.
"Outlines of Psychology," tr., p. 437.
'Brain, 1892, pp. 10, 11.
tention to abstract ideas. He states that the only motor element present in such attention is in the word itself, but the character of this motor element varies in individuals according to their mental type, whether visual, auditory, or motor.1 Now if the motor changes constitute the very nature of attention, attention itself must be dissimilar in persons of different types, and those in whom the motor element is most distinct will have the greatest power of attention. Different degrees of attention would be merely different degrees of motor adjustment. (3) Ribot fails to analyze the idea of movement. Ordinarily he refers to the purely physiological aspects of movement, and speaks of attention as their sum. But even when he is definitely concerned with the psychological aspect of movement,2 he refers to ideas of movement without analysis or definition of the term. The phrase, "idea of movement," can properly be used only in two senses: to mean (a) the idea to which movement itself is a stimulus; and (b) the idea upon which is based the knowledge that we have moved. Of the two definitions, the first presents the more legitimate use of the term. Just as the idea of sound is that to which the excitation of the auditory organ is a stimulus, so the idea of movement is the idea to which the excitation of the articular sensibility is a stimulus. By the second definition "ideas of movement" belong to the same class as ideas of magnitude or distance, and include in their content sensations of any and all sorts. But, in either case, the content of the term is a homogeneous or a heterogeneous mass of sensations. So it has come to pass that other psychologists, studying the same phenomena, reject Ribot's statement that the attention is essentially motor, and regard it as essentially sensory. The separation of these sensory and motor theories is an artificial one, but before completing their reconciliation, the differences between the two should be presented from the point of view of the "sensory" theorists.
II. Theory of attention as sensory. The sensory theory has been presented in a rather fragmentary way, by writers more directly concerned with the criticism of the motor theory than with the systematic formulation of their own views. The most complete statements of the position yet made are those of Bastian and Marillier. 4
Marillier defines attention as "a state of consciousness which is the result of the temporary predominance of one
Op. cit., pp. 84-88.
Op. cit., e. g., p. 72.
"On the Neural Processes underlying Attention and Volition,” Brain, LVII, 1892, pp. 1-34.
"Sur le Mécanisme de l'Attention," Rev. Phil., 1889, pp. 566-588.
representation over the representations which are coexistent with it at any given moment." He maintains that Ribot's analysis of the muscular movements in attention really proves "that what is essential here is the reinforcement of a representation, and that sensations are what determine this reinforcement. Movements are only a condition, as indispensable as you choose, but not an element of the phenomenon. What he [Ribot] succeeds in showing, after a long analysis of the mechanism of the voluntary attention, is the very important part played by muscular sensations in the memory of images and words."'2 Marillier goes on to say that after admitting that motor phenomena often play an important part in attention through the sensations which they excite, we must still protest against the implication that such peripheral excitation is the only way in which a representation may be reinforced. Account must also be taken of the interaction of the centres
upon one another. 3 His objection to Ribot's definition of attention as essentially motor is, then, up to this point, a two-fold objection.
(1) Admitting that motor phenomena have often a prominent part in attention, we must at the same time trace these phenomena backward to their rise in sensations, and forward to their excitation of the sensations of movement; so that on this ground alone attention should be called sensory rather than motor. (2) Ribot's account of the motor mechanism fails to recognize the interaction of sensory centres and of motor and sensory centres, and moreover-here Marillier introduces a yet more fundamental objection-the motor adjustment is often such that it fails to reinforce, or hinders the attention. This is ordinarily the case as attention grows more profound. Excitation of the sensory centres, up to a certain degree, occasions a series of muscular changes well adapted to reinforce the original sensory excitation by the sensations to which they give rise. By connate or acquired associations of certain sensations with motor adjustment, it is possible for an originally feeble sensation to be so intensified as to absorb attention. Take, for instance, the case of a dog perceiving the faint odor left in the track of a hare. The sensation has awakened strong impulses, and his attention is so absorbed that he can scarcely hear the shouts of his master.* But in both animals and men, if the excitation is further increased, its propagation is no longer confined to definite motor centres, so as to produce coördinated move
1Op. cit., p. 566.
2Op. cit, p. 572.
Op. cit., e. g., pp. 572, 587.
Op. cit., p. 574.
ments of a definite sort. It is diffused and results in irregular and disordered movements.
"They are no longer adapted to any end. A man makes gestures, speaks in a loud voice, walks back and forth, stops, starts again, waves his arms in the air, takes his hair in both hands; his mouth works in a thousand ways; sometimes his face becomes rigid, his eyes are fixed, his brows contracted, his forehead lined with wrinkles, his hands tremble, his voice is hoarse, speech is difficult, breathing is obstructed. If the excitation increases
still further, there is a change again: the muscles relax,
Marillier adduces as a subordinate proof of the lack of thorough coordination of the motor and sensory centres the fact that morbid states of the attention are not ordinarily associated with motor troubles.2
Illustrations of similar cases of attention, not covered by Ribot's theory, are presented in an article by Sully. The two most detailed descriptions can best be given in his own words:
"I was walking along a narrow lane lost in thought. I came on a lamp which shot its rays through the fog. I involuntarily stood still and fixated the lamp, thinking all the while intently on my psychological problem. When this intellectual effort relaxed, and not till then, I saw and recognized the lamp. Now here was energetic muscular action, and equally energetic concentration; but what was the relation of the two? That this involuntary assumption of the attitude of the seer, of the fixed head, convergent eyes, etc., somehow aided the process of mental concentration, is certain. But was this muscular adjustment the whole of the process? If so, I ought surely to have been mentally occupied by no abstruse problem of psychology, but with the concrete sensible object before my eyes, even though it had been far less brilliant and imposing an object than the lamp. The same partial independence of the process of attention and of the motor process appears, too, in ideational attention. If I think, for example, of a circle, with the eyes closed, . . . I not only have muscular sensations which tell me that the peripheral organ by means of which I acquired the idea is engaged, but I am aware of a motor impulse to retrace the curve of the circle. .. But now let us suppose that I am trying to visualize, not any particular form, but merely some shade of color, say, peacock blue. In this case I certainly find the motor element much less prominent. I am hardly aware, indeed, in this instance, of any ocular strain, and should say the eyes were in the easy and natural position, described by Helmholtz as the primary position, nor does attention resolve itself in this case into a renewal of the muscular action concerned in uttering the name of the color.
'Op. cit., p. 576.
2Op. cit., p. 580.
The Psycho-physical Process in Attention," Brain, 1890, pp. 145-165.
Indeed, I find that any thought of the name distinctly disturbs the visualizing process. And yet, though the muscular element in this case is, to say the least of it, considerably reduced, the active consciousness, the attention, is as clearly present as before."1
Sully compares the relation between attention and motor changes with "that which obtains between an emotion and the several sensory and motor phenomena which accompany it. Fear is always accompanied by characteristic physiological changes; and fear would not be fear but for these processes which contribute, in the sensations to which they give rise, characteristic features to the mental state. Yet when Prof. W. James of Harvard College not long since proposed to prove that emotion is nothing but the result of the organic changes and correlated sensations, most persons probably regarded the proposal as paradoxical."
Bastian is in substantial agreement with the parts of Marillier's and Sully's views that have here been presented. But he attacks two positions maintained by Marillier and Sully, not mentioned in the digest of their articles given above, because reserved for more extended notice here. The contested positions are : (1) The correlation of consciousness with efferent nerve currents in the cortex; and (2) the existence of motor and sensory centres in the cortex. After the discussion of these topics we shall pass on to the consideration of the second great class of theories of attention—the explanatory.
I. The correlation of consciousness with efferent nerve currents. With regard to the first position, the correlation of consciousness with efferent nerve currents in the cortex, Sully, Marillier, Fouillée, Waller and others maintain that there is such a correlation; while Bastian, Wundt, James, Münsterberg and others assert that motor centres or efferent currents have no correlative consciousness whatever. The point is not one of ultimate importance in the controversy between the sensory and motor theories, as is evident, indeed, from the fact that writers who agree in calling attention essentially sensory differ in regard to their ideas of motor consciousness." The opposing theories could be reconciled on the basis already suggested, i. e., the reference of the word "motor" to "ideas of movement," whether initiated solely by peripheral or also by central processes. Yet the subject is one of vital importance for the theory of attention in general, and it has been given such a prominent place in the sensori
Op. cit., pp. 156-157. Sully also cites Helmholtz's instance of attention to an object in the lateral regions of the field of vision. But recent experiments made by Heinrich in the laboratory at Vienna, show that there is a change in the accommodation of the eye when the attention is directed to the side of the field of vision or to mental operations. See Ebbinghaus' Zeitschrift, Bd. IX, Jan