Patients who have undergone a commissurotomy, "split brain patients," experience strange, acute post-operational symptoms: many have trouble speaking, or are completely mute; often they experience inter-manual conflict, where their hands cannot cooperate; when speech is possible, many remark that their left hand is behaving in a "foreign," "alien" manner, and they express surprise that it is acting so "purposefully." These symptoms fade over time. The long-term symptoms are much more difficult to distinguish in an everyday setting. Split brain patients function normally in social settings, except for slight memory problems. Pianists can still play the piano, artists can still paint. Once in an experimental setting however, more phenomena can be observed which point to the dramatic impact of full commissurotomy on cerebral function.
Commissurotomy patients are usually tested with a tachistoscope, a device that presents to the patient a screen with a focal point in the center. The tachistoscope then flashes a word, picture, or scene in the non-overlapping visual field of one eye. This is done faster than the eye can move, to ensure that only one hemisphere of the brain receives the input. When a key and a ring are flashed simultaneously in the left and right fields respectively, a normal viewer reports seeing "keyring". A split brain patient reports seeing only "ring". Even more notably, if the patient is told to use his left hand to pull the object he saw out of a bag, he pulls out a key. When asked what it is he pulled out, (without looking) the patient says, "A ring."
.....if you have additional questions, read more. Here is a link to a paper entitled Of Two Minds: click here
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