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Wednesday, October 16, 2002What Libet did was to measure electrical changes in people's brains as they flicked their wrists. And what he found was that a subject's ''readiness potential'' - the brain signal that precedes voluntary actions - showed up about one-third of a second before the subject felt the conscious urge to act. The result was so surprising that it still had the power to elicit an exclamation point from him in a 1999 paper: ''The initiation of the freely voluntary act appears to begin in the brain unconsciously, well before the person consciously knows he wants to act!'' And then there’s this: A subject, he said, would be repeatedly prompted to choose to move either his right or his left hand. Normally, right-handed people would move their right hands about 60 percent of the time. Then the experimenters would use magnetic stimulation in certain parts of the brain just at the moment when the subject was prompted to make the choice. They found that the magnets, which influence electrical activity in the brain, had an enormous effect: On average, subjects whose brains were stimulated on their right-hand side started choosing their left hands 80 percent of the time. And, in the spookiest aspect of the experiment, the subjects still felt as if they were choosing freely. ''What is clear is that our brain has the interpretive capacity to call free will things that weren't,'' he said. The brain is well known for its ability to trick the body - phantom pain in amputees, for example, or seizures that manifest themselves as visual or audio hallucinations; but that doesn’t mean that the essence of who we are is defined by our neurocircuits: And just because some processes in the brain are automatic does not mean they all are, he said. ''My take,'' Gazzaniga said, ''is that brains are automatic and people are free.'' Exactly. posted by Sydney on 10/16/2002 07:35:00 AM 0 comments 0 Comments: |
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