Have We Two Brains? (2)

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“Is There One ‘Left-Brain’ & Another ‘Right-Brain’?” (2)
A Myth that Began in the 19th Century

This “left brain/right brain” opposition originated in the First neurophysiology research. Intellectual capacities were often then described in two classes: critical and analytical aptitudes, on the one hand, and creative and synthetic aptitudes, on the other.



One of the major doctrines of neurophysiology from the 19th century associated each class to a hemisphere. In 1844, Arthur Ladbroke Wigan published A New View of Insanity: Duality of the Mind. He describes the two hemispheres of the brain as independent, and attributes to each one its own will and way of thinking: they usually work together but in some diseases they can work against each other.


This idea caught the imagination with the publication of Robert Louis Stevenson’s famous The Strange Case of Doctor Jekyll and Mister Hyde in 1866 which exploits the idea of a cultivated left hemisphere that opposes a primitive and emotional right hemisphere, which easily loses all control.



Paul Broca, a French neurologist, went beyond fiction to localise different roles in the two hemispheres. In the 1860s, he examined postmortem the brains of more than 20 patients whose language functions had been impaired. In all the brains examined, he noticed lesions in the frontal lobe of the left hemisphere, whereas the right hemisphere was still intact. He concluded that the Production of spoken language had to be located in the front part of the left hemisphere.



This was completed a few years later, by the German neurologist Carl Wernicke who also examined postmortem brains of those who had had language development disorders; he suggested that the capacity to Understand language is situated in the temporal lobe of the left hemisphere.

Thus, Broca and Wernicke associated the same hemisphere of the brain, the left, to two essential components of processing language – comprehension and oral production.

Brain Autopsy



Diagram of the Left Cerebral Hemisphere



Photograph of the Left Hemisphere "Normal"



Photograph of the Left Hemisphere "With the Damaged Broca's Area"

"Understanding the Brain", The Birth of a Learning Science, 2007, page 114, 115

(To be continued...)

Have We Two Brains? (1)

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“Is There One ‘Left-Brain’ & Another ‘Right-Brain’?” (1)
Two Brain Hemispheres Very Good Connected

The brain is made up of neuronal networks, it has functional areas that interact among themselves, and it is composed of Left and a Right Hemispheres. Each hemisphere is more specialised in certain fields than in others.

Do these facts justify the strange statements to be heard in everyday life, such as: “me, I’m more “Left-Brained””? or “women have a more developed “Right Brain”?”, Is there really a right “brain” and a left “brain”?



A rapid overview of the origin of these terms is needed to determine whether they correspond to facts, or if it is again a matter of questionable extrapolations of scientific data.

The Corpus Callosum Connects the Two Haves of the Brain

But to begin with, it needs to be underlined that the two hemispheres are not separate functional and anatomic entities: nerve structures connect them together (the Corpus Callosum) and many neurons have their cell nucleus in one hemisphere and extensions in the other. This alone should prompt reflection.






Lateralization of Brain Function:
It has been said that the “Left Brain” is the seat of rational thinking, intellectual thinking, analysis, and speech. It also processes numerical information deductively or logically. It dissects the information by analysing, distinguishing, and structuring the parts of a whole, by linearly arranging the data. The left hemisphere is the best equipped to deal with tasks related to language (writing and reading), algebra, mathematic problem-solving, logical operations. Thus, it can be believed that people who are rational, intellectual, logical, and have a good analytical sense “Preferentially Use their ‘LeftBrain’” and tend to be mathematicians, engineers, and researchers”.



The “Right Brain” has been called the seat of intuition, emotion, non-verbal thinking, synthetic thinking, which allows representations in space, creation, and emotions. It tends to synthesise, recreates three-dimensional forms, notices similarities rather than differences, and understands complex configurations. It recognises faces and perceives spaces. From this stems the Complementary Myth that people who are intuitive, emotional, imaginative, and easily find their way around, “Preferentially Use their ‘Right Brain’” and engage in the artistic and creative professions”.


However, despite the relative location of highest cerebral functions in the brain, it is always necessary to remember that this is One Brain with Two Hemispheres that are usually very well connected...

2-D images of the Corpus Callosum

"Understanding the Brain", The Birth of a Learning Science, 2007, page 114

(To be continued...)