QI | Why Do We Sleep?

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michael Longford : Sleep was invented to cure being knackered.

Timothy McLean : Why do we sleep? Because we get sleepy. Why do we get sleepy? ...We're working on that.

Stevie Cole : This is a perfect video for someone perusing YouTube at ungodly hours of the morning

Patrick Headland : David's wearing his special travel dressing gown!!

Jacob Seager : Awww Alan got that fact at the start from a previous episode from Stephen

Victor Dalloz : To anyone interested in the topic, I highly recommend the book "Why we sleep" by Matthew Walker (former Harvard professor, currently at UC Berkley). It's really a fascinating read.

New Message : Sleep is a conspiracy to disable the population for 7 - 9 hours a day, perpetrated by the De-Illuminati.

Arctic IceFox : The description still says Stephen Fry lol

Rosalie MYFHC : I'm a simple girl, I see Noel, I click

r0bw00d : Oh no, I need my alarm clock. I went an entire summer vacation without using one and wound up staying up later and sleeping later until I was keeping vampiric hours. Then I spent a week using my alarm clock to get myself back on schedule in time for school.

Zake Budek : ...perchance to dream - ay, there's the rub, for in this sleep what dreams may come...

Hubert Cumberdale : Noel's starting to look like a tired old woman.

angelstouch92 : A study I read recently showed that during the day things build up in the brain that essentially intoxicates you and sleeping helps clear it away. It's why if you don't sleep you show signs like being drunk.

Widdekuu91 : A better question; Why aren't I sleeping? The answer; This video, I'm watching it.

Ben Blackburne : I’ve always imagined that it might have been a way for our ancestors to get through the night, as it was so dark they couldn’t get much done so sleep would essentially they could sleep and then wake up when it’s morning. I’m not saying that this is the reason for sleep as it’s obviously not the main reason, but I’ve always been fascinated as to how sleep seems to be a time machine to the morning time. You can’t feel yourself sleeping, you just sort of wake up and it feels instant to when you went to sleep but really 8 or 9 hours may have passed. I’ve just always found that quite cool

Doctor Witten : The answer's a bit misleading. There's a rather popular book published recently by neuroscientist Matthew Walker, that's literally called Why We Sleep. It talks about how studies have indicated sleep's important role in improving mental functions like learning and memory; maintaining the health of your immune system ; and even helping reduce/prevent serious illnesses like dementia and cancer.

The Winspear : 2:34 My brain can't be cleaned because I'm dirty minded.

Lena Oxton : Your brain cells don't grow back either, and that's both a blessing and a curse. On the downside, you have terrible degenerative neural disorders you can never recover from, but on the upside, you won't have to go every two years for a new skull fitting for that big growing brain of yours!

Get the Joke! : My dentist said to me, that my gum has to come out.

Veronica Bean : I've had my gums trimmed...

M Standenberg : Can’t even answer the question “does our consciousness continuity break during sleep, in which case, do we effectively die and our bodies generate a new ego as we wake?”

Combicon : Was honestly expecting this to be a 'Nobody Knows' answer.

MeFirst please : I kinda didn’t want this to end

MrWombatty : The weirdest dreams are 'wanting-to-wee' dreams, especially those where I'm searching for a toilet but can't find one anywhere!

cloudsRniceC0M3 : Havent slept in month I can see smells Feel colours Touch sound

WuXiit : Wasn't this a question back when Stephen Fry was hosting? I seem to remember brain cleaning being the answer then.

youcometome9 : Why do we sleep ? Cuz U don't got to be WOKE all the time !

FutureChaosTV : "gum dresser" ;-)

Alagass : Boosh

Yj k : We evolved the ability to sleep as an easy excuse to get out of work

Chriscom28 : I had almost the exact same sleep analogy. Sleep is when our bodies undergo maintenance and repair and is best done while the body is less active.

Neil Bevan : Why do we sleep? It's the only legitimate excuse a person has to mentally get away from their partner.

nriab23 : That blond woman on the panal just isn't funny, I don't believe her jokes are supposed to funny rather her presentation of them, but even at that. I don't find either funny

Ras Putin : When we were a kid we don't like to sleep, now that we're adult we want to sleep all day!

sed8me69 : Regenerating, Hence we all wake up with that taste that's like fish fingers and custard 🤣

Mark Landgraf : Something tells me that David Mitchell would prefer jammies and a robe to be his normal everyday dress.

Jordan : Greatest feeling ever when you don't have school or work so you can sleep in. Wake up really early to go pee then go back to sleep.

Jeremy Baker : Itsa socialist phalisy to reduce workers hours. iworked 16 hr days now and then. It builds character you mongs.

Jack Versey : We don't know why we sleep? Really? Ask Matthew Walker, he's written a great book about it.

FortisConscius : I like Daniel C. Dennet's take on "why do we sleep?" The real question is "why do we wake?" - plants are a profoundly successful organism and they spend their whole lives asleep - seems a perfectly viable evolutionary strategy. (Waking is vastly overcomplicated by comparison. We wake because it gives us a competative advantage - moving where we need to be, not where we're drifting to. I.e. Outmanouevring predators and prey, etc. It's costly in development and maintenance but an advantage overall. No need to be awake all the time though - that's a good way to go crazy with information overload. The so-called Brain Cleaning seems apt alongside that line of reasoning.)

Thomas Cameron : We do know now. That old QI fact decay

Cyba IT : I would've thought it was obvious that we sleep to recuperate and recharge our bodies which is why babies sleep a lot and also if one is unwell.

Christian Buczko : This cannot be correct about energy saved when sleeping. It only works if you compare sleeping to lying down awake. If your highly active, you will burn far more energy than if lying down awake. So compared that to being asleep, your saving far more. You also sleep to allow your brain to sort out the accumulated crap, its like refreshing the cash memory on a computer. It fills up while awake, until your mentally exhausted, then you sleep. It's not physical, its mental. To refresh physically you eat, to resupply the energy used. I've tested this, and often go 3 days no sleep. If you don't exercise much, its your brains thinking which suffers, but you don't get physically tired. I've also gone without food, mentally you can handle it, but physically you become exhausted....

B uppy : It is my understanding that the body repairs itself during this downtime. Anecdotally, In one of the James Herriott stories he talks about getting ready to put down an ailing sheep, of which he could do nothing for. He had given it the painkiller/sleeping agent and was ready to give it the lethal injection, when he was called away. He'd came back a few days later to find the same sheep was alive and well, and frolicking, and not needing of euthanasia. We also tend to sleep more when we are ailing, additionally we do receive injuries to ourselves during the day that might overwhelm the body without the extra repair time of sleep. There also seems to be the time spent dreaming resolving issues. Dreams are powerful in their ability to encapsulize conceptually the problems/issues we experience during wakefulness and give us a different way of resolving them.

Benedict Harrison : Didn't Freud say it's because we secretly crave death?

MrUmandMrEr : An alarm clock? What on Earth is that?

Tom Lees : I swear Alan is a Time Lord

Brian The Destroyer : I mean something interesting for you lot to consider. Artificial Intelligence will probably need to sleep too if/when it gets made. Currently in computers there are many problems like buildup of spam files and fragmention and a whole bunch of other stuff. This problem will probably be many many times worse with AI than with normal computers. Now you could have background stuff working on all that but that would take a chunck of your resources. SO why do that when you can just have it "sleep" and clean itself up just as the theory suggests we do.

Dragon Curve Enthusiast : I'm disappointed they didn't mention sleep's role in learning and memory. There's a whole group of wikipedia articles about it: https://en.wikipedia.org/wiki/Sleep#Memory_processing It' not like that's a recent finding or especially contested (they brought up the energy consumption for goodness' sake!). I know a lot about this field and not even mentioning it makes me question the rigour with which the QI elves do their research. Or did they discuss it and it was just cut out for time?

Callum ash : Sleep was invented to dream Stephen is presenting again.