In the early 1960s, after experimenting on animal brains, neurosurgeons discovered that life-threatening cases of epilepsy could be treated by slicing through the part of the brain that connects the left and right hemispheres.
Patients could be cured of their seizures, but the two halves of the brain now operated independently, each with its own separate mental processes.
It was discovered that each half of the brain controls the opposite half of the body and that they each draw sensory input from one eye and one ear.
Generally, only one side of the brain has a good understanding of language and will have the ability to speak and write. In 95% of right handed people and 70% of left handed people, this will be the left side of the brain. By directing questions to this half of the brain, it was discovered that language skills are vital for logical and analytical thought processes.
The other side of the brain, usually the right side, specializes instead on interpreting visual imagery. It is also better at comprehending emotions. By directing questions to this half, it was discovered that understanding visual imagery was vital for conceptualizing how things work.
While the language dominant side of the brain focused on specific details, the visually dominant side of the brain was much better at seeing the whole picture.
In a few split-brain patients, both halves had a good understanding of language. In other cases, the mute half adapted over time by learning better language skills.
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~~Human Mind Evolution~~
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