The left brain vs. right brain myth - Elizabeth Waters

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The human brain is visibly split into a left and right side. This structure has inspired one of the most pervasive ideas about the brain: that the left side controls logic and the right side controls creativity. And yet, this is a myth, unsupported by scientific evidence. So how did this idea come about, and what does it get wrong? Elizabeth Waters looks into this long held misconception.

Lesson by Elizabeth Waters, animation by Daniel Gray.

Behold the human brain,

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

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

that the left side controls logic

and the right, creativity.

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

So how did this misleading idea
come about,

and what does it get wrong?

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

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

Internal regions, like the striatum,

hypothalamus,

thalamus,

and brain stem

appear to be made from continuous tissue,

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

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

such as movement and sight.

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

The visual system is even more complex.

Each eye has a left
and right visual field.

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

and both right fields
are sent to the left side.

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

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

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

because it gave the survival advantage
of quicker reflexes.

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

it's best off escaping to the right.

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

that rely on this left-right structure,

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

This misconception began in
the mid-1800s

when two neurologists, Broca and Wernicke,

examined patients who had problems
communicating due to injuries.

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

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

That captured the popular imagination.

Author Robert Louis Stevenson

then introduced the idea
of a logical left hemisphere

competing with an emotional
right hemisphere

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

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

examined patients who were missing
a hemisphere

or had their two hemispheres separated.

These patients showed a complete
range of behaviors,

both logical and creative.

Later research showed 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.

So one side of the brain may do more work,

but this varies by system
rather than by person.

There isn't any evidence to suggest

that individuals have dominant
sides of the brain,

or to support the idea
of a left-right split

between logic and creativity.

Some people may be particularly logical
or creative,

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

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

doesn't hold up well.

Solving complex math problems requires
inspired creativity

and many vibrant works of art
have intricate logical frameworks.

Almost every feat of creativity and logic

carries the mark of the whole brain
functioning as one.