The Split-Brain Discovery and the Left-Brain vs. Right-Brain Myth: Insights from Wilder Penfield and Roger Sperry

During the 1940s, Wilder Penfield, a famous Canadian neurosurgeon, treated epileptic patients at McGill University's Montreal Neurological Institute by surgically removing specific brain areas thought to be the origin of seizures. Prior to surgery, he stimulated discrete areas of the motor and sensory cortex with slight electrical impulses and, with his colleague Herbert Jasper, mapped the corresponding body parts that responded to the stimulation. Together, they constructed a homunculi map that represented the motor and sensory brain sites that affected specific body parts.

In the 1960s, the California Institute of Technology conducted studies that provided greater insight into brain lateralization or functional specialization. Although the left and right cerebral hemispheres are almost identical in appearance, they differ significantly in their functions. The two hemispheres typically communicate through the corpus callosum, a thick band of nerve fibers. However, since the 1940s, large portions of this band had been severed to treat severe epilepsy, resulting in split-brain patients, although these operations are rare nowadays.

Roger Sperry, a psychobiologist, and his graduate student Michael Gazzaniga tested the functioning of each hemisphere independently of the other in split-brain humans and monkeys. In approximately 1964, they discovered that while each hemisphere was capable of learning, one hemisphere had no awareness of what the other hemisphere had learned or experienced.

These studies' findings suggested that the left and right hemispheres are specialized in performing different functions. The left brain is primarily responsible for analytical, verbal, and language-processing tasks, while the right side is responsible for handling the senses, creativity, emotions, and facial recognition. Sperry won the Nobel Prize for his split-brain discoveries in 1981.

The belief that the left brain controls analytical and structured thinking, while the right brain influences creativity, is commonly known but has been largely discredited by neuroscientists.

Individuals are frequently characterized as either left-brain or right-brain thinkers. Left-brain people are believed to be more logical, fact-oriented, and linear thinkers who are concerned with structure and reasoning, while right-brained individuals are believed to be feelings-oriented, intuitive, creative, and musical. Although this may be an interesting topic for conversation, there is no compelling anatomical or physiological evidence to support these labels, and most scientists consider them a myth.