Experiments with “split-brain” patients have uncovered the surprising effects that the procedure can have on their perception. As the right and left eyes were feeding information to the other side’s hemisphere as normal, but in this case, neither hemisphere could communicate what they were seeing to the other, each side gave different responses to stimuli when one eye was closed (via Nature.com). For instance, the left half could recognize the person in a picture presented to their right eye, while the right side couldn’t. Per Gizmodo, this led to extreme cases of literal internal conflict, with each half having different feelings on the patient’s occupation, childhood bullies, and even treatment of their spouse. 

This latter example relates to a case where one side of a patient’s brain attempted to hit his wife while the other tried to stop the attack. An extreme scenario to be sure, but even relatively minor tasks could leave them at odds, as one half may attempt to close a book that the other is reading. Contrary to popular assumption, this does not leave the patient with their original self and a disconnected “alien” personality. A recent analysis of these studies suggests, both halves are thought to instead be best characterized as different framings of the same original consciousness (via Mind Matters).