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The human brain is split -

When you look at a human brain, it is quite visibly split down the middle.

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The nature of the split is the foundation of assumptions -

This physical split is what got early psychologists over attributing psychological theories, i.e. left side vs. right side.

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Even parts which are located in the center are split -

The central areas of the brain like the striatum, thalamus, hypothalamus, thalamus, and brainstem are made of continuous tissue but are also organized with left and right sides.

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Left brain controls the right arm and leg -

The left and right sides do control different body functions, like movement and sight. For example, the left side of the brain controls the right arm and leg, and vice versa.

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1800s psychiatrists -

However, overextending this idea is where problems arise. The misconception that almost all brain functions are either processed by the left side of the brain or right side of the brain can be traced back to psychiatrists in the 1800s.

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Their conclusion -

They concluded that after discovering that patients who struggled to communicate had damage to their left temporal lobes, communication was controlled by the left side of the brain.

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Scottish novelist Robert Louis Stevenson -

This idea captured the scientific community’s imagination, as well as author Robert Louis Stevenson's, who wrote about a logical left hemisphere competing with an emotional right hemisphere.

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Dr. Jekyll and Mr. Hyde -

The left and right sides of the brain became personified in the characters Dr. Jekyll and Mr. Hyde (one side of which is good and the other evil). This leads to associations of order and chaos, too.

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A separated hemisphere or damaged hemisphere -

Later on, psychologists found that if they examined the behavior of patients who had their hemispheres separated or were missing one hemisphere, they could still show a range of behaviors, both logical and creative.

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Certain functions are localized, but not entirely -

However, it was discovered that one side of the brain is more active than the other for some functions. Language is more localized to the left and attention to the right.

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It varies by system, not by person -

Therefore, one side of the brain might do more work, but this tends to vary by function, not by the person.

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Nobody has a dominant side -

There is no hard scientific evidence to suggest that individuals have dominant sides of the brain.

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Being artistic doesn't have to mean that the right side is dominant -

Some people may be tremendously logical and others may seem wholly creative and artistic, but this has nothing to do with which sides of their brains are dominant.

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Logic requires creativity -

For example, if we have to solve a seriously complex math problem, we may need to be tremendously creative to do so.

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Creativity requires logic -

Similarly, many vibrant works of art must be approached using logical methods. For example, at the simplest level, an artist may have to work out how big a person’s head must be in proportion to their legs.

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Compartmentalized functions that work together -

Almost everything our brain does requires the brain to function as one, despite it being compartmentalized at the same time.

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When we converse, we're doing multiple things at once (remembering, processing, etc.) -

So the brain is working in a modular fashion, which would be wrong to boil down to just left and right, and those sections of the brain also work together to carry out functions (like when we speak to someone, we may be using multiple areas, if not all).

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Consider how the marketing department works with the financial department -

The brain works how a governmental system works: it has many different functioning parts that (should) work together now and again.

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Why our brains may have evolved to work like this -

From an evolutionary standpoint, the benefit of this is that if one part of the brain fails, a person doesn’t become completely incapable of doing anything.

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How two sides work together: with abstractions, we cannot speak -

Large-scale, low-resolution abstractions (i.e. understanding something as the sum of its parts) tend to be the province of the right and high-resolution, detailed knowledge structures (i.e. language) tend to be the province of the left.

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How two sides work together: we must find our feet before chartering into unknown territory -

The fundamental difference shouldn’t be understood by just language vs. non-language or mathematical vs. non-mathematical, and rather mastered territory vs. relatively unexplored and not mastered.

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How two sides work together: stopping and starting -

Another loose generalization is that the left hemisphere will function by activating behavior and the right hemisphere can be considered to be concerned with the inhibition of behavior.

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How two sides work together: words and images -

The left hemisphere deals with word processing, whereas the right hemisphere deals with images.

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How two sides work together: linear and holistic thinking -

The left hemisphere is concerned with linear thinking and the right hemisphere is concerned with holistic thinking.

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How two sides work together: detail recognition and pattern recognition -

The left hemisphere is concerned with detail recognition, while the right hemisphere is concerned with pattern recognition.

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How two sides work together: generation of details and patterns -

Similarly, the left hemisphere is good for generating details and the right hemisphere is good for generating patterns.

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How two sides work together: fine motor action and gross motor action -

The left hemisphere may be considered to mostly manage fine motor actions (knitting), while the right hemisphere deals with gross motor action (running).

Sources: (Healthline) (National Geographic) (Harvard Health)

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