The two halves of the brain are connected through a bundle of fibers called the corpus callosum. There are times when that bundle of fibers is cut, either through injury or surgery. Often, these cuts result in little noticeable change. Other times, they force people into pitched battle against their other selves.
You are almost always of two minds. Most of the time they get along together very well, but on occasion, things get crazy. You just don't notice, because between the two of those minds, you almost always come up with an explanation. The major split in you, at any given time, is one between the two sides of your brain. The right half controls the left half of your body, and the left side of your brain controls the right side of your body. The vast majority of the planet is right handed, especially when they write. This may be because, in the majority of human beings, the left side of the brain is in control of language. And it's in charge of more than that.
The left side of the brain is generally in control of the following: language, math, and logic.
The right side of the brain takes over other functions, including: imagery, including facial recognition, music, and spacial relations.
There are times when one of the major connections between these two hemispheres are severed through injuries, stroke, or medical intervention. This is when things get interesting. At the very least, people will, with the right experiment, show that they are very different than someone with their brain intact. Show an image of an apple to someone's left eye, and ask them to pick up an object associated with it, and they'll pick up an apple. They just won't be able to express why they picked up an apple. Some will even say that they didn't see anything at all. Show a familiar face to left eye, and they'll recognize it, picking up a picture of the person, but they'll say they saw nothing. Show the face to the right eye, and they'll say that they saw a face, but it will just be a face - not a face they know. These people are mostly able to go about normal lives, because most information comes in through both eyes. Whichever part of the brain can deal with the information coming in, does deal with it, and the other side doesn't need to bother.
More developed people often have a harder time of it. A famous patient, Paul S., had a right hemisphere that had developed language function. This made him literally a man of two minds. The left side of his brain, when asked, wanted to be a draftsman. The right side wanted to race cars. Another patient had a right side of the brain that wasn't fond of reading, and would try to close, or throw away, the books that the left side was looking over. Another patient had one hand trying to dress him while the other hand undressed him. The most famous split-brain patient's left hand hated his wife. In what must have been a thoroughly terrifying time for both of them, but a moment of black comedy for an observer, the left side of his body tried to slap at his wife while the right side held it back.
More tellingly, an experiment was devised in which split brained patients were asked about their feelings. One man was asked how he felt about a memory of being bullied as a child. The left brain was indifferent. The right brain was still angry. Another was asked how he felt about himself. His right brain liked him. His left brain thought he wasn't good enough. When we have conflicting feelings about ourselves, we might simply be getting a big mash of different perceptions from each of the two hemispheres of our own brain. I think the lesson we learn here is simple. When we need to judge ourselves, we should focus on the right brain. When we judge others, go ahead and take the high road offered by the left brain.
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