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In the third millenium BCE,
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Mesopotamian Kings recorded and
interpreted their dreams on wax tablets.
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A thousand years later,
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Ancient Egyptians wrote a dream book
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listing over a hundred common dreams
and their meanings.
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And in the years since,
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we haven't paused in our quest
to understand why we dream.
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So, after a great deal
of scientific research,
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technological advancement,
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and persistance,
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we still don't have any definite answers,
but we have some interesting theories.
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We dream to fulfill our wishes.
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In the early 1900s,
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Sigmund Freud proposed that while all
of our dreams, including our nightmares,
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are a collection of images
from our daily conscious lives,
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they also have symbolic meanings,
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which relate to the fulfillment
of our subconscious wishes.
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Freud theorized that everything
we remember when we wake up from a dream
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is a symbolic representation
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of our unconscious primitive thoughts,
urges, and desires.
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Freud believed that by analyzing
those remembered elements,
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the unconscious content would be revealed
to our conscious mind,
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and psychological issues stemming
from its repression
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could be addressed and resolved.
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We dream to remember.
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To increase performance
on certain mental tasks,
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sleep is good,
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but dreaming while sleeping is better.
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In 2010, researchers found
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that subjects were much better
at getting through a complex 3-D maze
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if they had mapped and dreamed
of the maze prior to their second attempt.
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In fact, they were up to
ten times better at it
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than those who only thought of the maze
while awake between attempts,
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and those who napped but did not dream
about the maze.
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Researchers theorize that certain
memory processes
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can happen only when we are alseep,
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and our dreams are a signal
that these processes are taking place.
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We dream to forget.
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There are about 10,000 trillion
neural connections
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within the architecture of your brain.
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They are created by everything you think
and everything you do.
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A 1983 neurobiological theory of dreaming,
called Reverse Learning,
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holds that while sleeping,
and mainly during REM sleep cycles,
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your neocortex reviews
these neural connections
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and dumps the unnecessary ones.
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Without this unlearning process,
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which results in your dreams,
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your brain could be overrun
by useless connections
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and parasitic thoughts could disrupt
the necessary thinking
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you need to do while you're awake.
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We dream to keep our brains working.
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The Continual Activation Theory proposes
that your dreams result
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from your brain's need to constantly
consolidate and create long-term memories
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in order to function properly.
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So when external input falls
below a certain level,
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like when you're asleep,
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your brain automatically triggers
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the generation of data
from its memory storages,
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which appear to you in the form of
the thoughts and feelings
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you experience in your dreams.
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In other words,
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your dreams might be
a random screen saver your brain turns on
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so it doesn't completely shut down.
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We dream to rehearse.
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Dreams involving dangerous and threatening
situations are very common,
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and the Primitive Instinct
Rehearsal Theory
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holds that the content of a dream
is significant to its purpose.
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Whether it's an anxiety-filled night of
being chased through the woods by a bear
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or fighting off a ninja in a dark alley,
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these dreams allow you to practice
your fight or flight instincts
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and keep them sharp and dependable
in case you'll need them in real life.
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But it doesn't always have
to be unpleasant.
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For instance, dreams
about your attractive neighbor
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could actually give your reproductive
instinct some practice, too.
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We dream to heal.
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Stress neurotransmitters in the brain
are much less active
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during the REM stage of sleep,
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even during dreams
of traumatic experiences,
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leading some researchers to theorize
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that one purpose of dreaming is to take
the edge off painful experiences
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to allow for psychological healing.
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Reviewing traumatic events
in your dreams with less mental stress
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may grant you a clearer perspective
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and enhanced ability to process them
in psychologically healthy ways.
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People with certain mood disorders
and PTSD often have difficulty sleeping,
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leading some scientists to believe
that lack of dreaming
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may be a contributing factor
to their illnesses.
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We dream to solve problems.
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Unconstrained by reality
and the rules of conventional logic,
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in your dreams, your mind can create
limitless scenarios
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to help you grasp problems
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and formulate solutions
that you may not consider while awake.
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John Steinbeck called it
the Committee of Sleep,
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and researcher has demonstrated
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the effectiveness of dreaming
on problem solving.
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It's also how renowned chemist
August Kekule
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discovered the structure
of the benzene molecule,
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and it's the reason that sometimes
the best solution for a problem
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is to sleep on it.
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And those are just a few of the more
prominent theories.
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As technology increases our capability
for understanding the brain,
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it's possible that one day
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we will discover
the definitive reason for them.
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But until that time arrives,
we'll just have to keep on dreaming.