topic

Split brain

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What happens to a mind when you cut the cable between its two halves. To stop epileptic seizures crossing from one hemisphere to the other, surgeons severed the corpus callosum — and the patients, who seemed remarkably normal, turned out to be the cleanest natural experiment in the science of consciousness. With the hemispheres disconnected, you can show something to one half of the brain and not the other: the left hemisphere talks and the right hemisphere, mute but competent, answers with the left hand. Roger Sperry read the results as two separate spheres of awareness in one skull and won a Nobel for the programme; Michael Gazzaniga, working the human cases, found the left hemisphere's *interpreter* — the narrator that invents confident explanations for behaviour it did not cause and cannot see. A reading list around the operation and what it revealed: the surgery (Vogel and Bogen), Sperry's 1968 unity-of-consciousness claim, Gazzaniga's 1967 popular account and his 2000 and 2005 syntheses of the interpreter, and the Pinto 2017 challenge arguing the split brain divides perception but not consciousness. The bridge to [[topic:black-box|the black-box topic]] is the interpreter, which is the same [[concept:confabulation|confabulation]] the black-box literature finds in ordinary self-report and in a machine's chain of thought.