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Chapter 3: Movement and the Image or Centrally Excited Sensation
Margaret Floy Washburn
IN the last chapter we found reason for thinking that a stimulus produces an effect on consciousness when it initiates a motor response which is partly checked in its execution by a process of inhibition, through the influence of an antagonistic motor response. The conscious process that is thus directly occasioned by the action of an outside stimulus is called a 'sensation,' and may be further distinguished as a 'peripherally excited sensation,' to denote the difference between it and a centrally excited sensation or image. For we can get, as conscious experiences, sensations not only from outside stimuli, but by the processes which are commonly known as 'memory' and 'imagination.' Not only can I see red when red light is acting on my eyes, but I can call up a mental image of red, and even, with fair accuracy, images of a whole series of different shades and tones of red. I can not only hear the tones of a violin playing the "Prize Song" from the Meistersinger when the violinist is actually before me (or the phonograph is actually running), but I can sit here in my study, with no actual sound stimuli acting on my ears save the voices of the children across the street, and hear the tones of the violin through the entire air. The very important question now confronts us as to whether these images or centrally excited sensations are each one of them dependent on an incipient motor process, as the corresponding sensations would be if outside stimuli were acting.
A fact clear to any observation is that there often intervenes, between the giving of a stimulus and the making of a movement that an outsider can see, a long interval. A man is sitting in his business office. To him there enters an acquaintance and
( 28) asks him to write a check for one hundred dollars. The man of business says nothing, and makes no visible movement for a considerable interval of time. His friend knows very well, however, that the request has been heard and is being pondered, and waits patiently. At the end of a certain period, the business man draws his check-book and his pen to him and carries out the request. He responds to the original stimulus by making the same movements which he might appropriately have made to it at once: but during the interval between stimulus and response. he will report from introspection, a train of processes has passed through his consciousness which had no outside stimulus: which belonged to the class of centrally rather than peripherally initiated conscious processes. He may have heard in memory the words of another friend urging the claims of the cause to which lie is asked to give; he may have had a mental picture of some scene from his past.
Now, it would be quite possible to hold (d) that while these conscious processes are, taken all together, the whole series of them, caused by the delay in responding to the original outside stimulus, and thus conditioned by the initiation of the final motor response, the several and individual centrally excited processes, images, or thoughts, that filled up the interval were not, each of them, dependent on an initiated motor response of its own. On the other hand, I think a very good case can be made out for the hypothesis (b) that each of these centrally excited processes, thoughts, or images, is dependent on its own special motor response. If the first view (a) is maintained, we should suppose that the energy of the stimulus S, not finding full discharge into the motor pathways of the response. passes directly through a series of sensory centres and finally, by this indirect route, finds its way back into the motor outlet which by the direct route was not fully open. As the nervous process traverses each of the series of sensory centres, there occurs, it would be held, a centrally excited conscious process in quality like the sensation which the centre in question would mediate if it were excited by an external stimulus. To take a simple ex-
(29) -ample: the words, 'I promised my wife to give this money,' may pass through the mind of the man who sits silently pondering between the request for the money and the writing of the check. According to hypothesis (a), the energy of the stimulus (the request for the money) passes directly through a series of auditory sensory centres, and the accompaniment in consciousness is the mental hearing of the words in question. The implication of this view is that every sensory centre may have its functioning accompanied by consciousness under two wholly unlike physiological conditions. The first condition is when the energy of an outside stimulus reaches the centre. As we have seen, it appears probable that in such a case consciousness results only when the motor response is partly but not fully produced; only when excitation is partly balanced by inhibition. The second condition is when energy travels to the sensory centre directly from another sensory centre. But if the mere passage of the nervous process from one sensory centre to another is sufficient to call up a conscious process; if, that is, the traversing of a sensory centre by a nervous process coming from another sensory centre and on its way to a third is sufficient to bring an 'image' into consciousness, why is not the passage of the nervous process through a sensory centre on its way to a free motor outlet sufficient to cause consciousness in the case of the peripherally excited process' Yet we have noted the probability that the traversing of a sensory pathway by the nervous process is unaccompanied by consciousness when the motor pathway is free. On hypothesis a, then, the conditions for consciousness produced by outside stimulation, on the one hand, and the conscious processes, 'centrally excited,' involved in memory and imagination, on the other hand, would be quite unlike: the former would demand not merely the traversing of a sensory centre by a nervous current, but the partial inhibition of a motor discharge: the latter would demand merely the passage of the nervous current through the sensory centre from another centre.
Other arguments against hypothesis a will present them-
Chapter 3: Movement and the Image or Centrally Excited Sensation
Margaret Floy Washburn
IN the last chapter we found reason for thinking that a stimulus produces an effect on consciousness when it initiates a motor response which is partly checked in its execution by a process of inhibition, through the influence of an antagonistic motor response. The conscious process that is thus directly occasioned by the action of an outside stimulus is called a 'sensation,' and may be further distinguished as a 'peripherally excited sensation,' to denote the difference between it and a centrally excited sensation or image. For we can get, as conscious experiences, sensations not only from outside stimuli, but by the processes which are commonly known as 'memory' and 'imagination.' Not only can I see red when red light is acting on my eyes, but I can call up a mental image of red, and even, with fair accuracy, images of a whole series of different shades and tones of red. I can not only hear the tones of a violin playing the "Prize Song" from the Meistersinger when the violinist is actually before me (or the phonograph is actually running), but I can sit here in my study, with no actual sound stimuli acting on my ears save the voices of the children across the street, and hear the tones of the violin through the entire air. The very important question now confronts us as to whether these images or centrally excited sensations are each one of them dependent on an incipient motor process, as the corresponding sensations would be if outside stimuli were acting.
A fact clear to any observation is that there often intervenes, between the giving of a stimulus and the making of a movement that an outsider can see, a long interval. A man is sitting in his business office. To him there enters an acquaintance and
( 28) asks him to write a check for one hundred dollars. The man of business says nothing, and makes no visible movement for a considerable interval of time. His friend knows very well, however, that the request has been heard and is being pondered, and waits patiently. At the end of a certain period, the business man draws his check-book and his pen to him and carries out the request. He responds to the original stimulus by making the same movements which he might appropriately have made to it at once: but during the interval between stimulus and response. he will report from introspection, a train of processes has passed through his consciousness which had no outside stimulus: which belonged to the class of centrally rather than peripherally initiated conscious processes. He may have heard in memory the words of another friend urging the claims of the cause to which lie is asked to give; he may have had a mental picture of some scene from his past.
Now, it would be quite possible to hold (d) that while these conscious processes are, taken all together, the whole series of them, caused by the delay in responding to the original outside stimulus, and thus conditioned by the initiation of the final motor response, the several and individual centrally excited processes, images, or thoughts, that filled up the interval were not, each of them, dependent on an initiated motor response of its own. On the other hand, I think a very good case can be made out for the hypothesis (b) that each of these centrally excited processes, thoughts, or images, is dependent on its own special motor response. If the first view (a) is maintained, we should suppose that the energy of the stimulus S, not finding full discharge into the motor pathways of the response. passes directly through a series of sensory centres and finally, by this indirect route, finds its way back into the motor outlet which by the direct route was not fully open. As the nervous process traverses each of the series of sensory centres, there occurs, it would be held, a centrally excited conscious process in quality like the sensation which the centre in question would mediate if it were excited by an external stimulus. To take a simple ex-
(29) -ample: the words, 'I promised my wife to give this money,' may pass through the mind of the man who sits silently pondering between the request for the money and the writing of the check. According to hypothesis (a), the energy of the stimulus (the request for the money) passes directly through a series of auditory sensory centres, and the accompaniment in consciousness is the mental hearing of the words in question. The implication of this view is that every sensory centre may have its functioning accompanied by consciousness under two wholly unlike physiological conditions. The first condition is when the energy of an outside stimulus reaches the centre. As we have seen, it appears probable that in such a case consciousness results only when the motor response is partly but not fully produced; only when excitation is partly balanced by inhibition. The second condition is when energy travels to the sensory centre directly from another sensory centre. But if the mere passage of the nervous process from one sensory centre to another is sufficient to call up a conscious process; if, that is, the traversing of a sensory centre by a nervous process coming from another sensory centre and on its way to a third is sufficient to bring an 'image' into consciousness, why is not the passage of the nervous process through a sensory centre on its way to a free motor outlet sufficient to cause consciousness in the case of the peripherally excited process' Yet we have noted the probability that the traversing of a sensory pathway by the nervous process is unaccompanied by consciousness when the motor pathway is free. On hypothesis a, then, the conditions for consciousness produced by outside stimulation, on the one hand, and the conscious processes, 'centrally excited,' involved in memory and imagination, on the other hand, would be quite unlike: the former would demand not merely the traversing of a sensory centre by a nervous current, but the partial inhibition of a motor discharge: the latter would demand merely the passage of the nervous current through the sensory centre from another centre.
Other arguments against hypothesis a will present them-