WEBVTT

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Behold the human brain,

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it's lumpy landscape visibly split into
a left and right side.

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This structure has inspired one of 
the most pervasive ideas about the brain,

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that the left side controls logic

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and the right, creativity.

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And yet, this is a myth unsupported
by scientific evidence.

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So how did this misleading idea
come about,

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and what does it get wrong?

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It's true that the brain has a right
and a left side.

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This is most apparent 
with the outer layer, or the cortex.

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Internal regions, like the striatum,

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hypothalamus,

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thalamus,

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and brain stem

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appear to be made from continuous tissue,

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but in fact, they're also organized
with left and right sides.

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The left and the right sides of the brain
do control different body functions,

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such as movement and sight.

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The brain's right side controls the motion
of the left arm and leg and vice versa.

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The visual system is even more complex.

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Each eye has a left 
and right visual field.

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Both left visual fields are sent
to the right side of the brain,

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and both right fields 
are sent to the left side.

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So the brain uses both sides to make
a complete image of the world.

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Scientists don't know for sure
why we have that crossing over.

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One theory is it began soon after animals
developed more complex nervous systems

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because it gave the survival advantage
of quicker reflexes.

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If an animal sees a predator coming
from its left side,

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it's best off escaping to the right.

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So we can say that vision 
and movement control are two systems

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that rely on this left-right structure,

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but problems arise when we over-extend
that idea to logic and creativity.

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This misconception began in 
the mid-1800s

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when two neurologists, Broca and Wernicke,

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examined patients who had problems
communicating due to injuries.

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The researchers found damage to
the patients' left temporal lobes,

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so they suggested that language is
controlled by the left side of the brain.

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That captured the popular imagination.

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Author Robert Louis Stevenson

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then introduced the idea 
of a logical left hemisphere

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competing with an emotional 
right hemisphere

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represented by his characters
Dr. Jekyll and Mr. Hyde.

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But this idea didn't hold up when doctors
and scientists

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examined patients who were missing
a hemisphere

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or had their two hemispheres separated.

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These patients showed a complete
range of behaviors,

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both logical and creative.

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Later research showed that one side
of the brain is more active than the other

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for some functions.

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Language is more localized to the left

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and attention to the right.

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So one side of the brain may do more work,

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but this varies by system
rather than by person.

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There isn't any evidence to suggest

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that individuals have dominant 
sides of the brain,

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or to support the idea 
of a left-right split

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between logic and creativity.

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Some people may be particularly logical
or creative,

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but that has nothing to do with the sides
of their brains.

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And even the idea of logic and creativity
being at odds with each other

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doesn't hold up well.

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Solving complex math problems requires
inspired creativity

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and many vibrant works of art
have intricate logical frameworks.

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Almost every feat of creativity and logic

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carries the mark of the whole brain
functioning as one.