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Saturday, August 04, 2007

Does parallel processing in the brain show that there is really no mind?

Neurosurgeon Mike Egnor, who has said kind things about the forthcoming Spiritual Brain notes,
The parallel processing model of the mind has shown up in both materialist and dualist models of the mind.

Daniel Dennett has proposed that massive parallel processing in the brain is the cause of consciousness. He calls this his 'multiple drafts' hypothesis. He believes that the brain is constantly making 'drafts' of perceptions, and when there are enough drafts going on simultaneously, we become aware of ourselves- conscious.

There are a bunch of problems with Dennett's theory. Dennett's theory compares the mind to a computer, which is an intelligently designed model of dualism (hardware and software). Not a good analogy for a Darwinist.

Also, Dennett's theory leaves out irreducible first person experience like the actual experience of seeing the color red, etc. This is called 'qualia'. Also, the parallel processing theory implies that consciousness is in some way quantitative- that a blind person should be less conscious than a sighted person because the blind person has many fewer perceptions to process, or that we would be less conscious in a dark silent room, which is of course nonsense.

Another problem has been called the Chinese nation analogy. Imagine that all billion people in China decided to 'parallel process' at the same time- to do some brain function simultaneously, and to simultaneously communicate with each other about it. This would not cause the nation of China, as a single whole, to become 'conscious', in a way different from the individual consciousness of each person in China. There's no reason to think that any number of 'parallel' brain events would yield a unitary consciousness, and proponents of the theory have never proposed an actual mechanism as to how objective parallel processing becomes subjective first-person experience.

The parallel processing issue shows up in a more interesting way in the dualist beliefs of Wilder Penfield, who was the neurosurgeon who pioneered the study of electrical stimulation of the brain in conscious people (during surgery under local anesthesia) .

By stimulating the brain, Penfield was able to elicit all kinds of things- involuntary movements, sensations, thoughts, memories, emotions, etc. But patients always experienced these things not only subjectively but as observers. They always knew that these mental events were done to them, not by them. There was always an irreducible 'I' that could not be fooled or evoked.

Penfield studied thousands of patients this way, and on this basis was a convinced dualist. He believed the soul was distinct from the brain, and that his work empirically supported this view. I agree, and I've had the same experience as a neurosurgeon (without as many patients as Penfield had!)

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