The left and Right Side of our brains carry out different functions

In split-brain patients, the corpus callosum, which connects the left and right hemispheres of the cerebral cortex, has been surgical severed. This surgery is performed very rarely to help control severe epilepsy, it is done to stop the unwanted electrical activity travelling across the hemispheres which can cause the person to go unconscious.

By studying these patients, Dr. Roger Sperry made some remarkable discoveries about the human brain, for which he was awarded the Nobel Prize in 1981. What he found was that consciousness exists independently in the two different hemispheres and that the two sides can operate independently. The left side of the brain contains the speech center and can express itself verbally and logically, while the right side of the brain is more visually oriented.

In one of the experiments, an object was shown to the left visual field (which connects to the right side of the brain). Because the right hemisphere cannot process language, the patient was unable to say what the object was. However, they were able to pick up the matching object with their left hand. This is because the right hemisphere of the brain knew what the object was and could tell the left hand to pick it up, it just couldn’t express it with language.