The Divided Brain

by Iain McGilchrist

Why is the brain divided? If it is about making connections, why has evolution so carefully preserved the segregation of its hemispheres? Almost every function once thought to be the province of one or other hemisphere—language, imagery, reason, emotion—is served by both hemispheres, not one.

There is nonetheless a highly significant difference in how the two hemispheres work, giving rise to two wholly distinct takes on the world. Normally we synthesize them without being aware that we are doing so. But one of the two hemispheres can come to dominate—and just as this may happen for individuals, it may also happen for a whole culture.

The neuropsychological evidence shows that the right hemisphere pays wide-open attention to the world, seeing the whole, whereas the left hemisphere is adept at focusing on a detail. New experience, whatever its kind, is better apprehended by the right hemisphere, whereas the predictable is better dealt with by the left. And because the right hemisphere sees things in context, as inseparably interconnected, it recognizes the vast extent of what remains implicit. By contrast, because of its narrow focus, the left hemisphere isolates what it sees, and is relatively blind to things that can be conveyed only indirectly.

In humans, the left hemisphere controls the grasping right hand and the bits of language that enable us to pin down meaning unambiguously. It helps us manipulate and use the world, in pursuit of our aims. The left hemisphere's world is sharply delineated and certain, along the lines of the general's strategy map on the command room wall, where the complexity of the world is stripped away. Yet we still need to see the essentially human world as it is before we simplify and disconnect it. A general needs to be in touch with the world in which his soldiers actually fight. The knowledge that is mediated by the left hemisphere is knowledge within a closed system. It has the advantage of perfection, but such perfection is bought ultimately at the price of emptiness.

The right hemisphere's take on the world is far more complex and nuanced. Instead of distinct mechanisms, the right hemisphere sees interconnected, living, embodied entities. In communication the right hemisphere recognizes all that is nonverbal, metaphorical, ironic or humorous, where the left is literalistic. The right is at ease with ambiguity and the idea that opposites may be compatible.

There is a reason we have two hemispheres: We need both versions of the world.

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