Why do we dream? - Amy Adkins

8,620,344 views ・ 2015-12-10

TED-Ed


Please double-click on the English subtitles below to play the video.

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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 persistence,
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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 napped 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 asleep,
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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 research 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.
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