Left and Right Brain – Dual Process Theory

People often say things like “I’m right brained. I’m creative” or “I’m left brained. I can figure out any logical problem.” Although that’s a fun path for casual conversation, the left-right distinction is overblown and inaccurate. However, let’s not neglect the real distinction. This post examines one function, language, which has identifiable locations on one side only of the brain.

Laterality

Laterality is the dominance of one side of the brain in controlling particular activities or functions, or of one of a pair of organs such as the eyes or hands. Language is a crucial and very human function with laterality. Of all humans, 91% use the left hemisphere for language.

I will simplify by naming Left as the hemisphere performing language processing, although in 9% of the people language is done in the Right hemisphere. The important consideration is that one side is dedicated to language while the other is free from that requirement.

Left Brain

Two more specific language areas have been identified in the left hemisphere – Broca’s and Wernicke’s.

Left brain, language areas with connecting neural bundle. Motor cortex shown to orient view

Left brain, language areas with connecting neural bundle. Motor cortex shown to orient view

Broca’s Area has been identified as essential to our ability to generate speech. It is located in the frontal lobe, near the muscular control of throat, lips, and larynx with neural connections from the prefrontal lobe where decisions of what to say are made. It also has a bundle of nerves, the arcuate fasciculus, connecting it with the other major language focus, Wernicke’s Area.

Wernicke’s Area is essential to understanding speech. It is located in the temporal lobe, as the outer part of the auditory system, after vibrations are converted to morphemes and then to words.

Implications of Language

With language, we are comprehending experience into words and we are composing thoughts into words for speech.

The left brain focuses on literal as captured by words and logical as derived from the literal. It takes time for the words to be assigned (100 Step Post) and then more time for the results of logical thinking.  Also, it is well observed that it takes effort to think logically.

As a consequence of the time, the effort and the potential consequences, the left brain focuses on planning for beyond the immediate present.

Right Brain

The right brain has been observed as specializing in spatial analysis, although the laterality is not as exclusive as language. Spatial analysis includes not just what is “out there” but its physical relationship to our body.

The right brain retains the evolutionarily important function of responding to the immediate situation.

Sensory patterns are categorized but retain some of their imperfections in categories that words obscure. There is communication between the two sides of the brain.

Left-Right Communication

The corpus callosum is a wide band of 200 million neural axons which synchronize information across the brain’s central divide.

Here the brain is seen from above. On the right side an inch or so of the top has been lopped off. We can see the band of the corpus callosum fanning out after crossing, and joining every part of the two hemispheres.

Here the brain is seen from above. On the right side an inch or so of the top has been lopped off. We can see the band of the corpus callosum fanning out after crossing, and joining every part of the two hemispheres. (The front of the brain is at the top of the picture.)

Soon after the left brain has a language description of a part of its current situation, it sends that information to the right brain. The right brain can use that information, if it hasn’t already reacted to the stimulus (it can take ¼ to ½ second for the verbal assignment to be made).

Dual Process Theory

This independence of two core brain functions is called a Dual Process Theory. One process is immediate action. The other is planned action.

Left Hemisphere

  • Language
  • Literal. Fixed meanings
  • Logic
  • Effort to use
  • Planning. Delayed gratification

Right Hemisphere

  • Spatial
  • Patterns, Categories
  • Similarity
  • In control by default
  • Immediate response

The separation of function is sensible whether or not assigned properly to an individual hemisphere or even brain region. It’s just nice that the independent functions seem to be broadly aligned with one side of the brain or the other.

Mental Construction develops in greater detail the source and implication of dueling logical and similarity modes of thoughts – without reference to hemispheric locations.

Leave a Reply

Your email address will not be published. Required fields are marked *