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AP Psychology Split Brain Experiments
Transcript of AP Psychology Split Brain Experiments
Experiments Roger Sperry and his colleagues sought to disprove
the commonly-held belief that the brain was a
mish-mash of neuron firings and thought
processes; instead, their research - which includes
the now-famous split brain experiments - proved
that there are distinct sides of the brain, and that
certain actions correspond to each one. How did this experiment work? To perform these experiments, Sperry used a group of eleven patients who had the callostomy done, as well as a "control group" of eleven healthy people who's corpus callosum was still in tact. Sperry used an projector that would flash words very quickly (less than 1/10th of a second) on either the left side or right side of the screen, just long enough for one eye to notice. This makes sure that the image is directed to only one hemisphere. There was also a tray that covered a series of objects that matched the pictures, which each person would be asked to reach into and try to find an object by touch. Sperry also would use the projector to flash words or symbols to both hemispheres and would ask the participants to draw that symbol with their left or right hand. They split open people's brains?! Not exactly. The patients in Sperry's study suffered from severe cases of epilepsy and the surgery performed (called
corpus callosotomy) was a last resort in order to treat their
epilepsy. In the corpus callosotomy, the surgeon cuts the
corpus callosum in half. The corpus callosum connects the
two hemispheres of the brain, and is their main form of
communication. When it is cut, there are interesting behaviors that can occur. So what happened? Odd Behaviors Resulting From Surgery When the corpus callosum is severed, the connection between the two hemispheres is interrupted, which causes behavioral changes. Some examples of this type of behavior would be decreased reaction times (as the brain tries to figure out which hemisphere should take over), ability to focus on two completely separate tasks with the same amount of attention, and alien hand syndrome. Background What did Sperry seek to achieve? Sperry wanted to prove that the brain had distinct sections that had distinct attributes. He and his colleagues wanted to show, by experimentation, that the left brain and the right brain control separate aspects of conscious life. Experiments showed that patients whose corpus callosum had been cut often had conflicting results. For example, when a patient was shown a question mark to his right eyes and a dollar sign to his left eye, his left hand wrote the question mark. If asked what he saw in the projector, however, the patient said he saw the dollar sign. When the researchers showed the patient the paper he wrote the question mark on, he was genuinely confused and said he didn't see the question mark at all. Sperry and his colleagues saw that this phenomenon (which was repeated in all of the patients) was evidence of a brain that had distinct sides to it, not just a mass of neurons. This had big implications for the fields of psychology and neuroscience. Right Brain vs. Left Brain The right brain is better at processing visual and auditory cues, and operates the left hand. The right brain is big on nonverbal, such as tone of voice and body language; the right brain is, however, mute. It cannot control vocal behavior, nor can it make the person speak. The right brain also handles imagination and spatial tasks, such as judging distances and using maps. The left brain is better at linguistics, grammar and verbal tasks. The left brain handles mathematics better, is better at accessing memories, and is the only side that can speak. Writing also comes in the relm of the left brain, though the right brain can write as well.