Read Online The Illusion of Conscious Will by Daniel M. Wegner - Free Book Online Page A
Authors: Daniel M. Wegner
Tags: General, Psychology, Philosophy, Cognitive Psychology, Will, Free Will & Determinism, Free Will and Determinism
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anything back from them creates havoc.
Waterman still feels a sense of effort when he moves (Cole 1986), and this suggests that the loss of muscle feedback that he experienced did not eliminate this indication of his feeling of doing. So, perhaps the experience of will can come from merely having messages sent from brain to muscles. It might also be that without muscle sense, the visual perception of own movement gives sufficient feedback so that a sense of effort can be achieved. This is not an entirely telling case, though, because Cole mentions that Waterman’s loss of muscle sense may not be total. There is evidence from certain cases of paralysis, though, that also supports the conclusion that the feeling of effort may be more dependent on efferent (brain to muscle) than afferent (muscle to brain) neurons. When a muscle becomes completely unmovable, the experience of effortfulness of its movement also goes away, even if the muscle’s position can be sensed.
This phenomenon was illustrated graphically in an account by Ernst Mach (1906) of his own experience of suffering a stroke:
I was in a railway train, when I suddenly observed, with no consciousness of any-thing else being wrong, that my right arm and leg were paralyzed; the paralysis was intermittent, so that from time to time I was able to move again in an apparently normal way. After some hours [as] it became continuous and permanent, there also set in an affection of the right facial muscle, which prevented me from speaking except in a low tone and with some difficulty. I can only describe my condition during the period of complete paralysis by saying that when I formed the intention of moving my limbs I felt no effort, but that it was absolutely impossible for me to bring my will to the point of executing the movement. On the other hand, during the phases of imperfect paralysis, and during the period of convalescence, my arm and leg seemed to me enormous burdens which I could only lift with the greatest effort. . . . The paralyzed limbs retained their sensibility completely . . . and thus I was enabled to be aware of their position and of their passive movements. (174-175)
The experience of muscle effort in this case, it seems, must depend on having some movement capacity. With reduced capacity, as in fatigue or weakness or partial paralysis, the feeling of effort increased, whereas with no capacity at all the feeling of effort dropped to zero. The odd fact in Mach’s case, and one that has been substantiated in other, more modern instances (Rode, Rossetti, and Boisson 1996), is that these variations in the experience of effort or heaviness can occur even when the patient has some afferent (muscle to brain) pathways intact (Gandevia 1982; 1987). Mach could feel where his paralyzed limbs were. In this sense, Mach was the opposite of Waterman, in that he lost efferent (brain to muscle) control while retaining afferent (muscle to brain) contact, and in Mach’s case, the feeling of effortful movement was eclipsed entirely when he could no longer move. But without efferent control, unfortunately, there was also nothing for Mach to do (just as in the case of people who can’t wiggle their ears), so it is not too surprising that no effort was experienced. This case, then, is also not entirely conclusive about the source of feelings of effort.
It is interesting to note, though, that Waterman’s ability to use his visual sense to substitute for muscle sense indicates that in normal people the two senses may often be combined to allow judgments of movement. Lajoie and colleagues (1992) tested another patient who, like Waterman, had lost muscle feedback and had learned to guide her movements visually. The researchers were able to test this patient on a mirror drawing task (“Please copy these letters by watching your hand in the mirror”) and found that she was notably better than neurologically normal subjects. The bizarre mirror drawings most people produce
Waterman still feels a sense of effort when he moves (Cole 1986), and this suggests that the loss of muscle feedback that he experienced did not eliminate this indication of his feeling of doing. So, perhaps the experience of will can come from merely having messages sent from brain to muscles. It might also be that without muscle sense, the visual perception of own movement gives sufficient feedback so that a sense of effort can be achieved. This is not an entirely telling case, though, because Cole mentions that Waterman’s loss of muscle sense may not be total. There is evidence from certain cases of paralysis, though, that also supports the conclusion that the feeling of effort may be more dependent on efferent (brain to muscle) than afferent (muscle to brain) neurons. When a muscle becomes completely unmovable, the experience of effortfulness of its movement also goes away, even if the muscle’s position can be sensed.
This phenomenon was illustrated graphically in an account by Ernst Mach (1906) of his own experience of suffering a stroke:
I was in a railway train, when I suddenly observed, with no consciousness of any-thing else being wrong, that my right arm and leg were paralyzed; the paralysis was intermittent, so that from time to time I was able to move again in an apparently normal way. After some hours [as] it became continuous and permanent, there also set in an affection of the right facial muscle, which prevented me from speaking except in a low tone and with some difficulty. I can only describe my condition during the period of complete paralysis by saying that when I formed the intention of moving my limbs I felt no effort, but that it was absolutely impossible for me to bring my will to the point of executing the movement. On the other hand, during the phases of imperfect paralysis, and during the period of convalescence, my arm and leg seemed to me enormous burdens which I could only lift with the greatest effort. . . . The paralyzed limbs retained their sensibility completely . . . and thus I was enabled to be aware of their position and of their passive movements. (174-175)
The experience of muscle effort in this case, it seems, must depend on having some movement capacity. With reduced capacity, as in fatigue or weakness or partial paralysis, the feeling of effort increased, whereas with no capacity at all the feeling of effort dropped to zero. The odd fact in Mach’s case, and one that has been substantiated in other, more modern instances (Rode, Rossetti, and Boisson 1996), is that these variations in the experience of effort or heaviness can occur even when the patient has some afferent (muscle to brain) pathways intact (Gandevia 1982; 1987). Mach could feel where his paralyzed limbs were. In this sense, Mach was the opposite of Waterman, in that he lost efferent (brain to muscle) control while retaining afferent (muscle to brain) contact, and in Mach’s case, the feeling of effortful movement was eclipsed entirely when he could no longer move. But without efferent control, unfortunately, there was also nothing for Mach to do (just as in the case of people who can’t wiggle their ears), so it is not too surprising that no effort was experienced. This case, then, is also not entirely conclusive about the source of feelings of effort.
It is interesting to note, though, that Waterman’s ability to use his visual sense to substitute for muscle sense indicates that in normal people the two senses may often be combined to allow judgments of movement. Lajoie and colleagues (1992) tested another patient who, like Waterman, had lost muscle feedback and had learned to guide her movements visually. The researchers were able to test this patient on a mirror drawing task (“Please copy these letters by watching your hand in the mirror”) and found that she was notably better than neurologically normal subjects. The bizarre mirror drawings most people produce
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