Why do we sleep?

October 26, 2011 7:37 PM

Why do we sleep?
posted by Brandon Blatcher (68 comments total)

Extensive personal research has shown me that we sleep because even amphetamine psychosis has NOTHING on sleep deprivation for the creeping fucking horrors.
posted by elizardbits at 7:42 PM on October 26, 2011 [11 favorites]

In short, the fact that I average about 6 hours of sleep per night just might be the reason I can't ever remember anything. I'll be damned.
posted by secondhand pho at 7:42 PM on October 26, 2011

The question right now is "why the heck can't I sleep." Tis co.ing up 4am and I'm wide awake.
posted by seanyboy at 7:46 PM on October 26, 2011 [1 favorite]

As a kid i just assumed my brain had to defrag.
posted by mek at 7:48 PM on October 26, 2011 [15 favorites]

So, when we sleep, it's like we're defragging the disk.
posted by Devils Rancher at 7:48 PM on October 26, 2011

even amphetamine psychosis has NOTHING on sleep deprivation for the creeping fucking horrors.

Related post: "the complete, annotated, unabridged story of I how I went bat fucking crazy for three months"

That shit gave me the willies.
posted by Devils Rancher at 7:53 PM on October 26, 2011 [2 favorites]

Because otherwise they'd make us work.
posted by jonmc at 7:56 PM on October 26, 2011 [32 favorites]

The question for me is not "why" but "when." And the answer is "I really don't know." Because the days after I work the graveyard shift are invariably the days when there must be jackhammering in the street or feeding trees into a giant woodchipper right outside my house. Or when my neighbor must listen to loud pop punk at topfuckingvolume. And you don't get much sympathy trying to sleep at noon.

Yet night sleepers can be as cranky about it as they want. "Oh, I must have everything perfectly dark and if you so much as drop a spoon I will stomp out and glare at you."

The moral of my story is that people who sleep at night are wimps and if you are wondering why I am a bitch now you know.
posted by louche mustachio at 7:56 PM on October 26, 2011 [13 favorites]

So we can become Vikings.
posted by uncanny hengeman at 7:56 PM on October 26, 2011 [34 favorites]

The division of one day to the next must be one of the most profound peculiaries of life on this planet. It is, on the whole, a merciful arrangement. We are not condemned to sustained flights of being, but are constantly refreshed by little holidays from ourselves. We are intermittent creatures, allways falling to little ends and rising to little new beginnings. Our soon-tired consciousness is meted out in chapters, and that the world will look quite different tomorrow is, for both our comfort and our discomfort, usually true. How marvelously too night matches sleep, sweet image of it, so neatly apportioned to our need. Angels must wonder at these beings who fall so regularly out of awareness into a fantasm-invested dark. How our frail identities survive these chasms no philosopher has ever been able to explain.

- Iris Murdoch, The Black Prince
posted by Two unicycles and some duct tape at 7:59 PM on October 26, 2011 [26 favorites]

Wait. Did you just link to an Ask Metafilter competitor?!! Why were you even on there to get the link in the first place? TRAITOR!
posted by crunchland at 8:00 PM on October 26, 2011

As an adult I just assume my brain has to defrag.
posted by cjorgensen at 8:00 PM on October 26, 2011

Perchance to dream?
posted by tumid dahlia at 8:01 PM on October 26, 2011 [4 favorites]

Yet night sleepers can be as cranky about it as they want. "Oh, I must have everything perfectly dark and if you so much as drop a spoon I will stomp out and glare at you."

What about these neurotic types who can't get back to sleep when woken up by said spoon? What's wrong with you people?!

Zzzzzzzz. Wah, huh? Oh, spoon. Zzzzzzzz.
posted by uncanny hengeman at 8:01 PM on October 26, 2011

“Our dreams are a second life. I have never been able to penetrate without a shudder those ivory or horned gates which separate us from the invisible world.” -- Gerard de Nerval

Note that thinking of your dreams as separate but equal with your waking life may cause lobster-walking, mistaking of girls for mythological figures, addiction, and suicide.
posted by LucretiusJones at 8:18 PM on October 26, 2011 [4 favorites]

Personally, I think sleep is an evolutionary gag wherein the body moves all the bad-tasting chemicals from your bile ducts, into your mouth.
posted by tumid dahlia at 8:24 PM on October 26, 2011 [3 favorites]

I'm a bit sleep-deprived, and my brain keeps trying to replace "sleep" with "sheep" in the article.

I am also sheep-deprived, I suppose

better than sheep-depraved
posted by davejay at 8:35 PM on October 26, 2011 [2 favorites]

"Hey, I'm going to go lie down for a while and alternate total unconsciousness with vivid hallucinations, and then I'm going to get up and act like nothing happened. I think I'll repeat that every day or so for approximately 8 of every 24 hours. It's not weird at all."
posted by Eyebrows McGee at 8:37 PM on October 26, 2011 [33 favorites]

According to this (SLNYT), sleep scientists aren't really even sure what sleep is. For example, you brain is often far more active in REM sleep than it is when you're fully awake. Personally, I can lay in bed for an hour, fully awake, and still feel rested afterwards. Other times, I assume I've been fully awake the whole time, but then I remember a prior conversation with my wife that we never had. Slippery state, sleep.
posted by Gilbert at 8:38 PM on October 26, 2011

I'd tell you why we sleep, but I'm currently being chased by Marion Cotillard and holy fuck is she PISSED about something...
posted by Cool Papa Bell at 8:39 PM on October 26, 2011 [3 favorites]

Because we're tired.
posted by shakespeherian at 8:42 PM on October 26, 2011 [1 favorite]

better than sheep-depraved

Whatever you do, don't reach that point in your life where you're like "X sleeps until my next sheeps!"
posted by tumid dahlia at 8:45 PM on October 26, 2011

I sleep because I get bored.

Also, crazy.
posted by curious nu at 9:03 PM on October 26, 2011

Because we're tired.
posted by Scientist at 9:09 PM on October 26, 2011 [1 favorite]

Metafilter: Why you don't sleep.
posted by Panjandrum at 9:17 PM on October 26, 2011 [1 favorite]

I've heard it postulated that one reason cats of most species sleep so much may be to keep them from getting into trouble.
posted by longsleeves at 9:18 PM on October 26, 2011 [2 favorites]

Why do we sleep?

So we don't go fucking insane.
posted by 3FLryan at 9:24 PM on October 26, 2011 [1 favorite]

One of the most mind-bending things I ever learned was that cave researchers, who live for months on end underground, completely isolated from the cycle of days, will gradually and without fuss length their days to around 70 hours, being awake for 40 and then sleeping for 30. The cycle of regular downtime is an invariant, but there's no particular bond to a 24 hour day.
posted by fatbird at 9:30 PM on October 26, 2011 [1 favorite]

What do you mean, "we"?
posted by baf at 9:45 PM on October 26, 2011

Do you have a citation for that, fatbird? I'm interested in that kind of thing and would love to read more about the ways they adapted to that environment.
posted by winna at 9:50 PM on October 26, 2011

Some quick googling found this:

two German scientists conducted an experiment in which they locked up volunteers in a bunker where no sunlight could enter.

Unfortunately I'm remembering something from a while ago, like a Discovery article. The link I found indicates that humans actually did tend to fall into cycles that were multiples of days.
posted by fatbird at 9:57 PM on October 26, 2011 [1 favorite]

Sleep is less resource intensive. The question shouldn't be "why did we evolve to sleep?", but "why did we evolve to be awake so often?"
posted by painquale at 10:03 PM on October 26, 2011 [5 favorites]

Here's that link, I remember reading the article ages ago. Interesting stuff!
posted by tumid dahlia at 10:05 PM on October 26, 2011 [9 favorites]

That's it. Good catch, tumid.
posted by fatbird at 10:12 PM on October 26, 2011

We sleep because beds are so amazingly comfortable. What people did before beds were invented I have no idea...

(Also: not going mad is also a good reason to sleep.)
posted by lesbiassparrow at 10:17 PM on October 26, 2011

If you've ever lived for an extended period without artificial light you know that you sleep because it's boring at night.
posted by fshgrl at 10:21 PM on October 26, 2011 [1 favorite]

Personally, I think sleep is an evolutionary gag wherein the body moves all the bad-tasting chemicals from your bile ducts, into your mouth.

I saw a documentary about that once.
posted by louche mustachio at 10:21 PM on October 26, 2011

Personally, I think sleep is an evolutionary gag wherein the body moves all the bad-tasting chemicals from your bile ducts, into your mouth.


Which is why I tuck a couple of these in my mouth at night before I go to bed.
posted by Xoebe at 11:08 PM on October 26, 2011

I always assumed it was so my brain could sync up with the giant quantum computer sustaining reality at the end of time.
posted by AElfwine Evenstar at 11:16 PM on October 26, 2011

The question for me is not "why" but "when." And the answer is "I really don't know." Because the days after I work the graveyard shift are invariably the days when there must be jackhammering in the street or feeding trees into a giant woodchipper right outside my house. Or when my neighbor must listen to loud pop punk at topfuckingvolume. And you don't get much sympathy trying to sleep at noon.

I've been there, and working the graveyard shift is very close to the top of my list of "factors contributing to my becoming an alcoholic."
posted by treepour at 11:20 PM on October 26, 2011 [2 favorites]

What will really keep you up at night is the question:

Why would you do anything except, sleep?
posted by alex_skazat at 11:29 PM on October 26, 2011 [1 favorite]

To rest our eyes so we can play Minecraft the next day.
posted by zennish at 11:58 PM on October 26, 2011 [2 favorites]

well eventually you don't
posted by This, of course, alludes to you at 11:58 PM on October 26, 2011

Listen, we all saw what happened to Blanche.
posted by wreckingball at 12:05 AM on October 27, 2011 [1 favorite]

Modafinil ("wakefulness promoting agent")
posted by jcruelty at 1:53 AM on October 27, 2011

Because narcolepsy.
posted by Civil_Disobedient at 4:06 AM on October 27, 2011

To elaborate: I can hit full REM in less than 5 minutes. All the time, no matter what time of day it is, what I'm doing, how awake I am. I did a sleep study where they must have attached fifty different electrodes to me, piped them all through this box, like I was some kind of next-generation Radio Shack 101 Electronics Kit. They would have me look left, then right, then up, then down, then repeat. Then I'd close my eyes, and they gave me 10 minutes and ordered me to fall asleep.

I remember asking them how in the hell I was supposed to fall asleep with all these electrodes attached to me and doing all these eye movements, and they said if I had a problem then I shouldn't have any problem, and they were right. The bitch of it was, as soon as they detected REM rhythms they'd wake you up. You know how annoying that is? Right when you pass through the dream gates, to be yanked back into the waking world? Over and over again throughout the day.
posted by Civil_Disobedient at 4:29 AM on October 27, 2011

So we have time to repair our fragile systems by taking the stress off them long enough to let the day's wounds heal, and because the night is a good time to curl up somewhere safe from invisible beasties and just lie still. Dreams are just what happens when your brain is idling.
posted by pracowity at 4:35 AM on October 27, 2011 [1 favorite]

Sleep was also explained at length in this ask mefi thread last month.
posted by wanderingstan at 4:50 AM on October 27, 2011

I seem to be cathemeral. Good to have a word!
posted by running order squabble fest at 5:20 AM on October 27, 2011

You had to wake me up to ask me this?
posted by Splunge at 5:32 AM on October 27, 2011 [1 favorite]

Yeah, I don't think that 70-hour anecdote is right. Per the very good AskMe answer by Nomyte that wanderingstan linked to, absent daylight, people fall into a roughly 24-hour cycle. What I recall reading is that it's not exactly 24 hours, but slightly longer than that, like 25, and so clockwise such subjects' sleep cycles will move around the clock over time.

I'm a bit curious about sleep because my sleep has been disturbed and generally unusual for as long as I can remember. I've also suffered from chronic major depression for about as long as I can remember, too—which, per Nomyte's comment and many, many other sources, is probably not unrelated.

I have pretty much zero dream-latency, going into REM sleep immediately when I fall asleep and, as far as I can tell, have only REM sleep and none of the deep sleep I should be getting. Which probably explains why I'm always pretty tired. But, man, is my dream life active. I also have never had a stable sleep schedule, though I strongly tend to being a night-owl than otherwise. But left to my own devices with absolutely nothing to set a pattern, I don't fall into a cycle but, rather, just go through irregular cycles where I have interrupted sleep around the same part of the day for a number of days in a row, with it somewhat moving later or earlier, then maybe a big disruption (a long period of being awake or a long period of sleep) that changes where it's anchored, then rinse-and-repeat. It's not healthy, I'm pretty sure.
posted by Ivan Fyodorovich at 5:32 AM on October 27, 2011

Sleep and our need to do so has always fascinated me, even as a kid. Technically, it doesn't seem like we physically need it, but mentally we're dead in the water without it.
posted by Brandon Blatcher at 5:36 AM on October 27, 2011

According to the article part of sleep is growing new neurons, so the is a physical aspect to it. Although not below-the-neck wise.
posted by Splunge at 5:50 AM on October 27, 2011

I'm currently lucky enough to completely control my own time. I sleep until I feel like I should get up, and it is GLORIOUS. That is all.

Not an A-type personality, let me tell you.
posted by flippant at 5:55 AM on October 27, 2011 [2 favorites]

Civil_Disobedient,

It's called a Multiple Sleep Latency Test, or as i like to think of it: torture.
posted by jindc at 6:13 AM on October 27, 2011

cave researchers, who live for months on end underground, completely isolated from the cycle of days...

You're maybe thinking of Michal Siffre who spent 2 months in a French cave in 1962, and 7 months in Midnight Cave in west Texas in 1972. I got to spend about 6 hours there back in 1997.
posted by Devils Rancher at 6:23 AM on October 27, 2011 [1 favorite]

I can't speak for the rest of you, but I sleep because the kid wears me right the fuck out.
posted by gern at 6:40 AM on October 27, 2011

Eh, I wake up to eat and go to the bathroom. Otherwise, it would be just like that weekend in Tijuana during spring break.
posted by Brandon Blatcher at 6:52 AM on October 27, 2011

Sleep is absolutely fascinating, really, isn't it. Not in the least for the process of dreaming, but also for the general personal and social implications of sleep.

First and foremost, sleep cements memory; short-term memory is codified and moved into long-term memory. This is an active, observable process and one of the reasons babies and infants sleep to such a degree; because they are literally always, constantly learning and creating new, short-term memories.

Secondly, sleep puts the body in a state of rest, reducing the energy load of the brain and muscular systems in favour of the digestive and immune systems. If you imagine the body has a finite amount of energy, shutting down the Big Consumers (brain and muscles) allows the systems to focus more on efficient processing of food and immune response.

In fact, one of the reasons fasting has such a healing effect on the physical body is it deletes the energy demands of the digestive system from the process, thus allowing the immune system to consume a great quantity of clean energy (from fat, essentially).

On a tangent, this is the reason that overeating is so harmful. All of the food that humans consume have microbes and bacteria. When we ingest food and other substances, the immune system must release agents to neutralise harmful bacteria and pathogens. Thus, if one is overeating, the immune system is 'cleaning' inputs that the digestive tract cannot absorb, thus there is a deficit of immune products to do deep cleaning and repairs.

Thirdly, the immune system teaches you kung fu, to use a neologism from the Matrix. One of the nascent theories on dreaming is that the brain runs threat scenarios to prepare itself for potential threats in the real environment.

When you fall asleep, the reticulum paralyses limbs via the musculature, thus the brain is free to simulate real-world experiences by generating false stimuli. The machinery that normally makes your legs move activates, however the legs do not move. This simulation environment allows the brain to process short-term memory and review it for perceived threats. When a threat is encountered, the brain can 'act it out' and prepare the amygdala, essentially programming the fight or flight responses of the body.

A genius effect of evolution, as once fight or flight kicks in, there is little perceptual processing of external stimuli, rather the brain executes a programme. And where does that programme come from? The pre-programming.

Psychologists are split on the intersection of dreams and emotions, however there is a school of thought that says the stimulus and imagery of dreams are less relevant than the emotions that play out in the dream. The individual figments of imagery have subconscious tags. Your father may not represent your literal father but may represent authority or power. Your car may not represent that shining piece of metal in the driveway but rather pride... or expenses... or freedom.

It really doesn't matter because you'll probably never have a clear indication of that symbolic attachment without deep study and meditation. Regardless, the brain puts the scenarios together and runs them... again and again... playing out what could happen. What happens if you run? What happens if you punch the threatening person in the face? What happens if...

You then execute that programming -- the emotional programming -- in reality, and over subsequent sleep cycles, fine-tune it so that you become better and better as assessing threat. After all, in the risk-reward continuum, if a risk destroys you, that is not a good risk. However, if you 'flight'ed from everything, there can be no achievement, no challenge. Thus the brain slowly builds up a lexicon for understanding what are real threats and what are simply new situations.

This is closely tied into the fact that anxiety and excitement have the same biological signalling -- a change in the environment. Anxiety is perception of negative outcome and excitement is perception of positive outcome. That process is fine-tuned in moving short-term memory in to long-term, reviewing the data and refining the programmes.

Finally, there is a tremendous social component to sleep as well. If one is asleep, one is a great target for predation. Thus, to really enjoy some snoozing, one has to first and foremost be safe. That is, when I sleep, you have to be fending of the (Lions, Tigers, Bears, Romans, Mongolians, Ottomans). Thus, 'rich' societies have great 'access' to sleep and can therefore create strong memories and better 'programmes'.

This is why "sleeping" with a partner can be more intimate than "sex", because of the inherent vulnerability involved in the process and the necessary trust that whoever you are sleeping with is not going to steal your (candles, gold, salted meats, kidney, MacBook, horses, children).

Further, apparently, the 'natural' sleep cycle previously was in two four-hour segments. Light (candles, oil) was expensive, thus, societies would fall asleep at sunset, after dinner (when the tummy was full and the digestive system took over). People would awake at random shifts throughout the night and 'share' light, in the form of socialising in a central location. This permitted the light resources to be shared across a great number of people. They would sit and chat for an hour or two, and then retire for another four hours until natural light returned.

There is a whole lot more to be said on the derivative meaning of sleep. Too much sleep indicates depression -- either avoiding life or spending a prolonged amount of time trying to work things out in the simulation. Too little sleep inhibits both the physical functioning of the body as well as the functioning of the mind and basic personality. If the personality is indeed composed of memory itself, interrupting the formation of the memory process leads to a dysfunction of the personality itself.

Overall, I have just butchered dirty many concepts of psychology and neuroscience, however whilst my cleaver is dull and my cuts are inaccurate, the song remains the same: sleep itself is fascinating on unlimited levels. Witness the cultural fascination with a little movie about multi-layered dreaming earlier this year...
posted by nickrussell at 7:52 AM on October 27, 2011 [13 favorites]

I think one of the things I'm grateful for, physiology-wise, is that I can go to sleep practically instantaneously. Every morning, I wake up, and my roommate talks about how she couldn't sleep at all, only managed to go to sleep at 2 am, and then was awakened by the stupid neighbors practicing guitar, and why don't they stop doing that and she's going to complain to the landlord etc. etc. and I nod politely and agree to call the landlord, but really I'm thinking, damn, it sucks to be you, because I was asleep at 11:30 pm, didn't hear the guitar and woke at 7:00 am feeling refreshed. My boyfriend reports that I often fall asleep within seconds. Sometimes we play guessing games in bed, twenty questions about a person or an object or the like. We often have games like this:
HE: Male?
ME: No
HE: Dead?
ME: Yes
HE: 20th century?
ME: Yes
HE: European?
ME: zzzzzzzz
I usually remember everything perfectly until when I actually fall asleep. (This can, understandably, sometimes be a bit frustrating to the boyfriend.)
posted by peacheater at 8:06 AM on October 27, 2011

Why? To get eaten by a clown.
posted by clvrmnky at 8:29 AM on October 27, 2011

I think one of the things I'm grateful for, physiology-wise, is that I can go to sleep practically instantaneously.

Ditto. This was a problem in college when sleep deprived and in large lectures, i.e. wake up with the lights out and some guy shaking your shoulder saying "hey buddy" ... or in clubs ~4am, etc.

But yeah, once you become a square adult with all the distractions and annoyances (neighbors)of square adultdom, the ability to fall asleep instantly is a huge bonus, I think. I don't think it's physiological, though. I had a hard time falling asleep as a kid. I learned how to sleep better.

My boyfriend reports that I often fall asleep within seconds. Sometimes we play guessing games in bed, twenty questions about a person or an object or the like.

See I wouldn't fall asleep doing that. I can keep talking all night if you want. And I can't fall asleep at all if I can hear my young daughter awake.

But usually, I will fall asleep before anyone has time to ask any questions. When I kiss my wife, say goodnight, and lay my head down, it's literally 5 seconds or less. *knock on digital wood*

First and foremost, sleep cements memory

I'd say first and foremost (i.e. infants), sleep helps you grow.

I found it odd the main link didn't mention it.

The "why do we dream?" question is about as relevant and effable as "why are we here?"
posted by mrgrimm at 8:59 AM on October 27, 2011

here's a better link... the relevant soundbite:

"Altered hypothalamic activity associated with initiation of sleep results in a major peak of growth hormone secretion unrelated to hypoglycemia or changes in cortisol and insulin secretion."

Growth hormone secretion during sleep; Y. Takahashi, D. M. Kipnis, and W. H. Daughaday (full study PDF)
posted by mrgrimm at 9:06 AM on October 27, 2011

er, the "why do we sleep" question, that is. the "why do we dream?" question is actually more interesting. imo. and just as thin a post. ;)
posted by mrgrimm at 9:07 AM on October 27, 2011

I feel like the thread has had enough life to point out this: Quora, the fourth best way to get an answer online after Ask.Metafilter, supports image tags of some sort.
posted by filthy light thief at 9:21 AM on October 27, 2011

"In the naval engagement that Augustus won of Sextus Pompeius in Sicily, just as they were to begin the fight, he was so fast asleep that his friends were compelled to wake him to give the signal of battle: and this was it that gave Mark Antony afterwards occasion to reproach him that he had not the courage so much as with open eyes to behold the order of his own squadrons, and not to have dared to present himself before the soldiers, till first Agrippa had brought him news of the victory obtained. But as to the young Marius, who did much worse (for the day of his last battle against Sylla, after he had marshalled his army and given the word and signal of battle, he laid him down under the shade of a tree to repose himself, and fell so fast asleep that the rout and flight of his men could hardly waken him, he having seen nothing of the fight), he is said to have been at that time so extremely spent and worn out with labour and want of sleep, that nature could hold out no longer. Now, upon what has been said, the physicians may determine whether sleep be so necessary that our lives depend upon it: for we read that King Perseus of Macedon, being prisoner at Rome, was killed by being kept from sleep; but Pliny instances such as have lived long without sleep. Herodotus speaks of nations where the men sleep and wake by half-years, and they who write the life of the sage Epimenides affirm that he slept seven-and-fifty years together." -- Montaigne
posted by blucevalo at 10:15 AM on October 27, 2011 [1 favorite]

Wait. Quora lets users insert images into their posts?

WHAT. THE. FUCK. MATT?!?!?!11111???//?
posted by slogger at 11:49 AM on October 27, 2011