You all constantly hear about how getting plenty of sleep is essential to staying healthy and that you can reap tons of benefits from snoozing, but do you ever think about why sleep is necessary in the first place? Why do living creatures have the need to sleep, and what causes exhaustion? According to Dr. David G. Meyers at Hope College in Michigan, "sleep commands roughly one-third of our lives - some 25 years, on average". It is quite obvious that we need to sleep in order to "…feel refreshed, sustain better moods, and perform more efficient and accurate work". But isn't entirely clear why sleep is necessary and why humans require a certain amount of it. Psychologists are able to dish out a handful of fascinating theories as to why sleep evolved and they are totally worth checking out!
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This is one of my favorite theories as to why sleep is necessary. As humans our lives shut down at night when we lose the light from the sun. This lack of light may not seem like a huge disadvantage to the modern-day human; however, our distant ancestors would have had a terribly difficult time being productive in the dark because they would have been unable to hunt, gather, or travel by night. Psychologists theorize that sleep evolved in order to force humans to hide and sleep until the sun rose. Falling asleep ensured that our ancestors would not attempt to wander around in the dark and encounter dangerous predators or lose their way.
Differences across Species
This theory makes sense of the different sleep requirements that various species require. This is a branch off of the previous theory, and it makes a very interesting point! An animal's size and needs can affect its sleeping pattern. For example, a bat requires a whopping average of 20 hours a sleep a day! On the other hand, a giraffe requires a mere two hours. Because a giraffe is large in size and bright in color, any attempts to hide itself would be totally futile!
Aside from sleeping for protection, catching enough zzzs is necessary for restoring and repairing brain tissue. There is a theory that animals with a high waking metabolism, such as bats, need to sleep for longer periods of time due to the fact that they burn through their energy so quickly while they are awake! Also, when we sleep, our brains take the opportunity to sift through our neuron connections, organizing and eliminating the ones that we don't use. Have you ever run a file cleanup or "disk optimization" on your computer? Think of it like your brain going through "files" in your mind, compacting some and deleting others to provide you with the storage space you need to function more efficiently!
Another interesting sleep theory is that sleep is an integral part of restoring your memory. When you're asleep, your mind is able to stabilize and solidify memories in a way that it can't when you are awake. Many studies show that people who sleep after learning new information retain it to a much higher level than those who learn and then stay awake for another few hours. If you're a student or you're learning a new language, taking a nap after studying and hitting the books at night before you sleep will help you preserve all of your study efforts without any extra exertion!
Some psychologists suggest that dreams serve the purpose of sparking our creativity and helping us develop solutions to our problems! There have been countless instances in which dreams have inspired noteworthy literary, artistic, and even scientific achievements. Our minds and subconscious are far more powerful than we even realize, and our brains know that they can experiment in our dreams with a lack of negative consequences. This theory really appeals to the cliché problem-solving advice: "sleep on it!"
A sleep and dream theory that I find incredibly fascinating is that dreams are simply a mind's way of deciphering neural static. Neural static is a garbled and random neural activity. It is an instinct for our brains to make sense of information, grouping thoughts together like pieces of a puzzle in order for us to understand a bigger picture. Because neural activity is so random when you're asleep, your brain attempts (quite unsuccessfully) to make sense of all the static buzzing around in your mind. This is most likely why dreams hardly ever make any sense and why they can be so utterly bizarre!
Sleep and Growth
One final theory that explains the evolution of sleep is that sleep helps support growth! During deep sleep, your pituitary gland is responsible for releasing a growth hormone that is essential for muscle development. As you age, you release less of this hormone and as a result, you spend less time in deep sleep. A newborn baby requires an average of sixteen hours of sleep, and a full grown adult requires only half of that amount. As we age, we release less of a certain hormone, causing us to both grow and sleep less!
Learning about these theories in my psychology course really opened my eyes to the flurry of reasons why sleep is necessary, and now I understand much more about my mind and my body. Did you find any of these theories interesting? Which one (or ones) do you agree with most?
Source: Meyers, David G. Exploring Psychology. Ninth ed. New York: Worth, 2014. Print.
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