30-Second Psychology: The 50 Most Thought-provoking Psychology Theories, Each Explained in Half a Minute - Christian Jarrett 2011
Sperry’s split brains
The brain has two hemispheres, left and right, each of which is connected and coordinated across a bundle of fibres called the corpus callosum. During the 1960s, the neuroscientist Roger Sperry discovered that when this bundle is severed, the human brain not only continues to function, but each side is, to some degree, independently conscious. Sperry was studying patients with seemingly untreatable epilepsy who had had their corpus callosum surgically cut in an attempt to stop seizures spreading. Many years before, neuroscientists examining patients with brain damage had discovered that certain functions, such as language, were more reliant on the left hemisphere, whereas visual abilities were more reliant on the right. Sperry realized that ’split brain’ patients allowed these differences to be explored in detail. He found, for example, that a word presented to the language-specialized left hemisphere was read and understood as normal, whereas a word presented to the language-minimal right hemisphere went unrecognized. But when the task was to draw what the word described, the patient could produce sketches from words presented to the visual-arrangement-specialized right hemisphere, but not the other way around.
When the brain’s hemispheres are surgically divided, consciousness can be split in subtle and interesting ways.
Popular culture got carried away with Sperry’s discoveries and we often hear the inaccurate idea that the right side of the brain is ’creative’ while the left side is ’logical’. These are general tendencies, not absolutes, and are about as useful as suggesting that people from one country are ’emotional’ while those from another country are ’practical’. If anything, Sperry’s work highlighted that the brain is a complex network and that our abilities rely on the coordination of both hemispheres for their full potential.
The next time you’re in two minds about something, spare a thought for those epilepsy patients with a severed corpus callosum, literally splitting their minds in two.