Read Online The Illusion of Conscious Will by Daniel M. Wegner - Free Book Online Page B

arise because they have trouble integrating the mixed signals they receive from sight and from muscle feedback. The two senses tell them different stories about where the pencil might be and they get mixed up as a result. With-out muscle feedback, and after learning to control action with vision alone, this patient was able to do something that baffles everyone else.
    The studies of muscle sense seem to indicate that the feeling of effort that is part of the experience of conscious will may depend on outward signals from the brain to muscles and sometimes also on muscle sense, the returning signals from muscles to brain. It would be nice if we could sum things up at this point and head home for dinner and an evening of television, but we’re not done. There is a major additional mystery: The feeling of conscious will doesn’t always seem to go away when body parts go away.
    Phantom Limbs
    That’s right, people can sometimes feel they are willing movements that don’t even happen. Most people who have had an arm or leg amputated continue to sense the presence of the limb thereafter, what Mitchell (1872) called a “phantom limb.” Of some 300 amputees in prisoner-of-war camps during World War II studied by Henderson and Smyth (1948), for instance, fully 98 percent were found to experience a phantom limb, felt as a pleasant, tingling sensation that was not painful. Some people do experience such a limb as having pain, however, which makes it a particularly miserable burden.
    Here’s the intriguing part. A phantom limb can often be perceived to move, either involuntarily (as when the stump of the limb is pushed by someone else) or voluntarily (as when the amputee tries to move it). The apparent voluntary movement is not merely a gross motion of the limb, either, because the person may very well feel separate parts moving and changing position in relation to each other. Fingers may be wiggled, elbows or knees bent, arms or legs twisted—all with nothing really there (Jones 1988). As a rule, the more distal parts of the limb (fingers, toes) are felt more strongly than the proximal parts (nearer the actual stump), apparently because the distal parts are represented more fully in the brain. Movement of the phantom limb becomes more difficult with time, and eventually the ability to “move” the digits may be lost even though the limb may still be perceived to exist. As the feeling of voluntary movement subsides over a period of months or years, the limb may “telescope” toward the body such that the last sensations the person may experience are only of the digits extending from the stump.
    A fascinating feature of phantom limb movement is that, at least on first analysis, it suggests that the intention to move can create the experience of conscious will without any action at all . For a number of researchers working in the late nineteenth century, this feature of phantom limb movement was taken as evidence that messages from the brain to the muscles could be perceived by the brain before they even left the brain to go to the muscles (Helmholtz 1867; Mitchell 1872). After all, there were no muscles out there, only a phantom. Phantom limb movements always occur consciously and are not spontaneously made (Jones 1988), and this also seems to substantiate the idea that there is some consciousness of a signal being sent to the absent limb.
    Further research has found, however, that the sense of moving a phantom limb voluntarily depends on the continued functioning of sensory nerves and muscles in the stump. Henderson and Smyth (1948) observed that every voluntary movement of a phantom limb was accompanied by a contraction of the appropriate muscles in the stump, and that if the remaining muscles in the stump had lost their nerve connections, the ability to move the phantom was lost. If the brain has nowhere to send the movement commands, in other words, it no longer senses that the movement is occurring. The continued feeling