The Brain: Lateralisation of Brain Function

“The great pleasure and feeling in my right brain is more than my left brain can find the words to tell you.” – Roger Sperry


The left hemisphere of our brain functions in reading, writing, speaking, arithmetic, reasoning and understanding. It is considered the major hemisphere because it has proven far easier to comprehend and study. Our right brain to this day is still very much misunderstood.  We do know that the right hemisphere is immensely important to our creativity, expression and social skills such as recognising faces and tone of voice. However, diseases that afflict the right side of our brain still befuddle scientists today.

Popular psychology and self-help books discuss the left versus brain dominance. Creative, free-spirited people who have excellent social skills but are poor at maths are considered right brain dominant; whereas, logical, analytical, linear people lacking creativity are considered to be left brain dominant. Like most self-help fads, there is some truth behind these claims. Most people generally rely on one side of the brain more than the other whilst thinking. This is known as brain lateralisation, a term that grew out of work by American neurobiologist, Roger W. Sperry. That is to say that, people that rely more on their left brain whilst thinking do posses a more logical, linear, objective perspective than those who rely on their right brain more. However, it is important to understand that all humans rely on both hemispheres for day to day activities and hardly anyone displays solely the characteristics of one hemisphere.


The left and right hemispheres are connected by a large band of neural fibres called the corpus callosum. It allows for messages to be carried between the two hemispheres. Sperry along with other psychologists, Myers and Gazzinga, concluded through the splitting of the corpus callosum of animals left them relatively normal. These findings were then applied as a form of treatment for extreme cases of epilepsy – a neurological disorder marked by sensory disturbance, loss of consciousness and convulsions as a result of excessive nerve firing in the brain. In these extreme cases of epilepsy the excessive firing would start in one hemisphere but cascades into a storm of firing across the corpus callosum to the other hemisphere. A surgery in which the corpus callosum was split was seen as the only alternative to treat the worst symptoms. The surgery enabled the patients to carry out normal life without the constant life-threatening symptoms; however, through these experimental surgeries the function of the corpus callosum was discovered.

Sperry and Gazzangia found that the corpus callosum did, in fact, have significance.  It enables communication between the two hemispheres. Each hemisphere continues to learn after the operation; however, the two hemispheres remain unaware of any learning and experience of the other side.


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