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8 The Fictional Self
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chapter eight The Fictional Self Michael S. Gazzaniga, Ph.D. What makes us human? This question has been debated for centuries —what is it that di≠erentiates us from the rest of the animal kingdom? The philosophers have talked about “persons” as narrators of the self, as rational agents, and as social beings who can form theories about themselves and those with whom they interact. We neuroscientists seek the human spark by looking at the mechanics of brain function, hoping to find the intersection of biology and personhood. Thus, neuroscience has tended to define our species by focusing on our cognition and language skills. That is, we humans think, control our actions with conscious thought, and communicate through language to make our thoughts known. But the more neuroscientists come to understand about the human brain, the more we want to identify the specifics of human consciousness. After all, much of the research on the human brain comes from finding similarities with other species’ brains—be it the mouse or the chimpanzee. In fact, one of the major recent discoveries in cognitive neuroscience—mirror neurons —was made in monkey brains. Mirror neurons have opened the door to understanding concepts such as empathy and theory of mind (more on this later). But while the motor neurons in a monkey’s brain may fire when it sees another monkey pick up a banana, the monkey has not sat down to figure this out in a laboratory setting. In other words, we may have a theory about monkeys , but monkeys don’t have the same level of theory about us. There’s a big di≠erence between the monkey’s instinctive learning, and even its ability to communicate, and ours. What is it about human consciousness that is unique? The deeper we delve, the more neuroscience seems to agree with the philosophers: what makes us persons, rather than merely creatures, is our ability to create a story about ourselves, and we want that story to hang together , to make some kind of coherent sense, even if our brains have to distort our perceptions to do so. Neuroscientific research has identified a mechanism , which I call the interpreter, in the left hemisphere of the human brain that generates such a narrative. No other species can sit around the campfire weaving experiences into a saga of personal or cultural identity. The human brain’s interpreter was discovered over a period of years of research on “split-brain” patients. I began this work in the 1960s with Roger Sperry, examining the behavior and cognition of epileptic-surgery patients. In some epilepsy patients, the corpus callosum, the nerve tract system that connects the left and right brain hemispheres, is severed to stop seizures. Postsurgery , the patients are able to return to normal life, seizure free. In fact, they appear perfectly normal unless they are tested in specific ways, which reveal that while they can still name and describe, in a normal way, information receivedbytheirleftdominanthemisphere ,theycanrespondtoteststimulipresented to their right hemisphere only through nonverbal means—they are unable to provide a spoken response. The challenge of split-brain testing was to find ways to communicate with the nonverbal, right hemisphere, without letting the left hemisphere know what we were asking. We devised nonverbal modes of responding to questions , such as patients’ pointing to answers instead of speaking. To explain how we did this, understanding a basic principle of brain organization is important : if you fix your eyes on a point—for example, on a dot—all visual information to the right of the dot travels through the visual nerve pathways to your left brain hemisphere, and everything to the left of the dot is projected exclusively to your right hemisphere. For instance, in a “simultaneous concept” test, we presented split-brain patients with two pictures, projecting one to the right hemisphere by showing The Fictional Self 175 [3.224.147.211] Project MUSE (2024-03-29 07:28 GMT) it only to the left visual field and one to the left hemisphere by showing it only to the right visual field. We then spread several other pictures in front of the patients and asked them to point to the ones related to the pictures they had seen. In one such test, we flashed a picture of a chicken claw to the left hemisphere and a picture of a snow scene to the right. When choosing the related pictures, the patient, as expected, pointed to...