>Parfit begins this chapter by making a refreshing break from the philosophical practice of thought-experiments, building instead on actual cases documented in medical literature. These are the famous ‘split-brain’ cases, in which surgeons severed the corpus callosum, the main bundle of nerve fibres connecting the left and right hemispheres of the human brain, as a treatment for epilepsy. Cutting the connection reduces the severity of epileptic attacks by preventing seizures from spreading from one hemisphere to the other. But there are side-effects.
>The effect, in the words of one surgeon, was the creation of ‘two separate spheres of consciousness’. (p 245)
>This radical conclusion was strongly based on clinical evidence. The hemispheres of the brain have long been known to show strong left-right differentiation. Images from the left side of the visual field flow to the right hemisphere, and vice versa. The right hemisphere primarily controls the left hand, and vice versa. Parfit describes split-brain patients being presented with two colours: red in the left half of their visual field and blue in the right half. The patients are questioned about what they saw. Answers originating in the left hemisphere are given by the right hand, and vice versa. A patient is asked how many colours he can see. The response from each hand is, “One.” When asked to identify the colour, the left hand responds, “Red” and the right hand responds “Blue”. W-What the fuck Veeky Forums?
I actually studied this a little bit in my epistemology class. It's super strange. They report things like when they're trying to pick out an outfit and can't decide, one arm will just surprise them by grabbing something. The different sides of the brain can't communicate and I think our verbal thinking (the sort of inner monologue) is from one side so it isn't aware of stuff the other side deals with.
Just checked. Wernicke's area and Broca's area are both on the left side of the brain and those are our main speech areas.
It is sort of similar to two consciousnesses coexisting in the same body but I'm disinclined to call it that, as consciousness is pretty vague a concept. Plus, I think it's more like you're just not aware of what you're thinking.
Parker Kelly
It's a pretty good argument against the dualist notion of "consciousness" underlying the alleged hard problem since it shows how belief and reporting behavior aren't at all immediate and can totally be fucked with.
Confused language. You don't have a brain, you are a brain. And a split brain means there are two of you.
Andrew Adams
Good posts. The inner dialogue isn't to be conflated with thought itself. Awareness of experience has no direct access to knowledge of experience or of inner thought.
Xavier Fisher
I don't get it. The hemispheres can't communicate, they're testing out processes that can be carried out by one hemisphere, so both hemispheres give out a different answer. How does that imply 'two separate spheres of consciousness'?
Mason Morgan
I often wonder if there are more "spheres of consciousness" in my brain than just me. Maybe the subconscious is actually also conscious, for example.
