Correcting Brain Myths (1): Left Brain — Right Brain

I originally wrote this as the first in a series of posts on brain myths for teachers. But this is just as relevant for many people because the left brain right brain myth is one of the most popular and pervasive brain myths despite many years of trying to debunk it. The myth states that the left brain is the logical, rational, reasoning side of the brain, and this gives us “left brainers”, those logical people. The right brain, according to the myth, is the creative and emotional side giving us those creative and emotional “right brainers”. This is fundamentally wrong, but we do have two hemispheres and there is some location specific functioning. But first let’s understand the fascinating history to this myth.

Sperry & Split-Brain Patients

Much of the location in hemispheres dates back to the work and research of Sperry and his graduate student Gazzaniga on so-called split-brain patients in the 1960s and 1970s. This led to a Nobel prize for Sperry in 1981.

Split-brain patients had had the corpus callosum, the bridge between the hemispheres in the brain, cut through to relieve epilepsy — it always amazes me what neurosurgeons did and do do! They hence had two unconnected brains in their skull. Outwardly these individuals behaved completely normally — which in itself is pretty amazing — but on closer inspection and research some strange anomalies appeared:

  • Words project to the left hemisphere could be remembered and verbalised, but not when to the right.
  • But the words projected to the right hemisphere, that couldn’t be verbalised, could, however, be drawn by the left hand (controlled by the right hemisphere).
  • When projecting words to right hemisphere study participants could pick up the right object but couldn’t verbalise what it was.

Sperry hence saw that the right had language recognition but no articulation, and that the two hemispheres in split-brain patients did not acknowledge the existence of each other. A pretty impressive finding and one that could, and would, fascinate us human beings.

He did, however, presciently, warn that “experimentally observed polarity in right-left cognitive style is an idea in general with which it is very easy to run wild… it is important to remember that the two hemispheres in the normal intact brain tend regularly to function closely together as a unit”

Despite saying this, we did run wild with the concept of right and left hemisphere personality styles, and this was triggered by some high-profile newspaper articles. Read on:

The Myth grows

According to Psychology Today:

The New York Times Magazine in 1973 published an article, “We are left-brained or right-brained”, that began: “Two very different persons inhabit our heads, residing in the left and right hemispheres of our brains, the twin shells that cover the central brain stem. One of them is verbal, analytic, dominant. The other is artistic…” Two years later, Time magazine featured the left/right story. In 1976, Harvard Business Review published “Planning on the Left Side and Managing on the Right” and the following year, it was Psychology Today’s turn to trumpet the idea. The 1981 Nobel Prize in Physiology or Medicine that Sperry received for his split-brain research opened the floodgates.

Indeed, the floodgates were open with many different theories and even personality tests around the left/right brain personality. The myth is not so much a myth as a dangerous oversimplification. The brain does indeed have two hemispheres, and there is localisation of some functions, but even these always operate in tandem with other areas of the brain including alternate hemispheres. For example, language is normally based in the left hemisphere, but as a highly complex cognitive and behavioural process uses resources from many areas such as Broca’s and Wernicke’s areas in the left hemispheres but also for tone and intonation in the right hemispheres. The left seems to be more specialised in words and grammar and the right on the flow and tonality of language. This would suggest different processing of languages also for tone-based languages such as Chinese.

What the left and right hemisphere actually do

So, if we do have two hemispheres, and the logical creative description is fundamentally flawed, then what do the hemispheres actually do? Here are some functions which have been localised

  • Sides of body: left part of brain controls right side of body, and right side of brain controls left side of body
  • “Shield and Sword” — the dominant handed-side of the brain control approach and attack behaviours, “Sword”-based behaviours. The non-dominant handed side of the brain controls avoidant and defensive strategies — this is the “Shield”. These are also known as “Avoidance” behaviours in psychology. These are therefore opposite depending on one’s handedness.
  • Language (vocabulary and grammar) are clearly domains of the left hemisphere.
  • Emotion expression and recognition of these seems to be the domain of the right hemisphere
  • Internal attention seems to be controlled by the left and external attention by the right
  • Focused attention is left and broad attention (scanning) is the right

The best explanation and exploration of the hemispheres is that of Iain McGilchrist and his book “The Master and His Emissary”. He eloquently, and in scientific detail, outlines why he sees the right hemisphere as the Master and the left as its Emissary and why, tragically, in modern society we seem to have become slaves to the left. Iain McGilchrist lists these functions for the right and left and this is the description I find most useful:

Left vs. Right

  • Specific vs. Broad
  • Static vs. Evolving
  • Fixed vs. Moving
  • Object vs. Living
  • Mechanic vs. Organic
  • Isolated vs. Contextualized
  • Denotative vs. General
  • Abstract vs. Embodied

We can see here that the left is the domain of the specific and focused, much of this can be considered “cognitive ability”, but not exclusively. The right is the more generalist, embodied and human view of the world. McGilchrist cites the left as having “knowledge of the parts” and the right as having “wisdom of the whole”. His short animation video (11:24) can be viewed here.

Iain McGilchrist The Divided Brain

There are also a bunch of fascinating and intriguing aspects of the left and right brain. One is that the right hemisphere can take over functions lost in the left hemisphere but the left seems unable to take over functions lost in the right hemisphere. For example, following brain damage to the visual cortex we know that the right hemisphere can compensate for brain damage to the left hemisphere hence blindness in the right eye due to brain damage is unusual, but the left hemisphere cannot compensate for the right hemisphere so blindness in the left eye due to brain damage is vastly more common. This underlines the concept of the right being the generalist which can therefore rebuild other functions and the left as being the specialist.

Mixed personalities seem to be high performers

One particularly negative concept of the left and right concept is that one is better than the other, or that you are either, or that you are fixed in this. Indeed our research into personality using our Human Behavioural Framework (a fully comprehensive model of human personality) also shows that high performers in business, entrepreneurship, and teaching, show high cognitive abilities and high intuition which goes against the left/right principle but also against many other personality measurements which measure these on a sliding scale and not separately.

So high-performing brains seem to be not just more cognitive but better at everything! Here’s to balanced brains!

Some References

General reading

Why the left brain right brain myth will probably never die:

Roger Sperry’s Split Brain Experiments (1959–1968):

Divided Brain — Divided World, Iain McGilchrist:

The Master and his Emissary, Iain McGilchrist:

Scientific Reading

The split brain: A tale of two halves:

Scientific Papers

Left Brain, Right Brain: Facts and Fantasies:

Neuromyths in education: Prevalence and predictors of misconceptions among teachers:

Dispelling the Myth: Training in Education or Neuroscience Decreases but Does Not Eliminate Beliefs in Neuromyths:

The brain and human behaviour, in business, society, learning, and health.

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