Yawning, Déjà vu & Hypnic Jerks

We can send a man to the moon (at least we can create television shows that convince naive 1970s people that we’ve sent men to the moon), but there’s all sorts of weird but ordinary things we have no real explanations for. For instance:


Why is yawning contagious? Science guys have mapped brains while their owners watch other people yawn and have figured out that people’s compulsion to yawn in response stems from “the apparent deactivation of a brain area called the left periamygdalar region.” The more strongly a participant reported wanting to yawn in response to another person’s yawn, the stronger was this deactivation. 

This same brain region is also where the unconscious analysis of emotional expressions on other people’s faces takes place. Interestingly, researchers have found that the more self-aware a person is and the more they are able to see things from another person’s perspective, the more likely they are to find yawning contagious.

Schizophrenics and babies under a year don’t find yawning contagious. You can watch your cat or dog yawn and it won’t make you want to yawn probably because you don’t have the same level of awareness or empathy with their feelings/emotions.

We tend to think everyone finds yawning contagious – watching a yawn, thinking about yawning, even reading or talking about yawning (Are you yawning yet?) But really, only 40 – 60% of people automatically find yawning contagious and yawn themselves.

One theory for contagious human yawning is that it’s a primitive response that used to help us communicate and coordinate sleep schedules. Group synchronization is apparently important for species survival. Science guys say it’s “action without understanding, like when a flock of birds rises to the air as soon as the first bird does it – perhaps because he notices a predator.”

I don’t know. Why of all things, would we have retained that for so long when we’ve lost other, more important things like the ability to chew hides and turn them into soft, supple leather garments? Because that would come in handy still, wouldn’t it?

Hypnic Jerks

You know when you’re about to fall asleep and you suddenly feel like you’re fallings and you experience an“involuntary myoclonic twitch during that state of hypnagogia? Ya, that’s called a hypnic jerk. Who knew?

Not me, that’s for sure and nobody else seems to know why, exactly these things occur. The best theory science guys can come up with is, that as our heartbeats and breathing slow down and muscles begin to relax and stop working, the brain, for some reason, thinks this means the body is falling. So, of course the brain tries to make the body catch itself.

Hmmm. Lame theory if you ask me. Other people think it’s just a twitch similar to people sometimes twitch when they’re dying. (Do they?) The hypnic jerk is kind of a last ditch reflex to keep the body functioning – like those ER paddles (CLEAR!). The brain registers the body shutting down for sleep as some sort of emergency and sends stimulation to the body to jerk it back to life.

This one makes more sense to me, though it’s kind of scary that the brain doesn’t seem to know what’s going on in its own body. But, they do say that hypnic jerks happen mostly when a person is overly tired, sleeping in an uncomfortable place or has had his sleep schedule disrupted. So maybe we can cut the brain some slack under those circumstances.

There are also hypnic jerks that happen to some people when they wake up. They awake suddenly with what (to them) sounds like a very loud snap or crack which seems to come from the middle of the head. Sometimes there’s even a blinding flash of light.

Have you ever woken up with a hypnic jerk?

Déjà vu all over again

There are more than 40 theories as to what déjà vu is and what causes it, ranging from reincarnation to some sort of short-circuit in our brain’s memory centres.

What I find most interesting about déjà vu is that while about 70% of the population has experienced some kind of déjà vu, it is most common in adolescents and young adults and wanes significantly as we age. Come to think of it, I can’t remember the last time I experienced déjà vu. How about you? Wait…. I knew I was going to say that….

Anyhow, I don’t think déjà vu has anything to do with past-life experiences. I also don’t think it has anything to do with precognition. Déjà vu doesn’t foresee an event,  but happens during an event. And it’s usually a really normal, boring event. What would be the point of being forewarned about someone asking you to pass the chianti at dinner?

However, those busy science guys have pretty much determined, beyond doubt, that déjà vu is associated with temporal lobe epilepsy. It can occur just before a seizure or even during a seizure.

So, since déjà vu also occurs in people who don’t have epilepsy, it stands to reason that the phenomenon is somehow related to similar brain activity.

How or what exactly is occurring is still up for debate, but my favourite explanation is that there is simply an error in the brain between the timing of perception and cognative process. So, stuff is happening and this sensory information is making its way into the brain’s memory storage room as per usual, but there’s some sort of glitch en route which results in a short delay in perceiving the information. This short delay makes it seem like you’re experiencing the event and remembering it at the same time.

But, if you don’t like that explanation, maybe you agree with Freud who says déjà vu is “an expression of repressed desires.” Or perhaps you’re more of a Jungian who suggests it comes from “the tapping the collective unconscious”?

Or maybe you’re more of a physicist who believes that particles that can travel backwards in time (tachyons) and that déjà vu is a result of time loops and multiple universes. Perhaps déjà vu is a form of neurological “time travel”?

22 responses to “Yawning, Déjà vu & Hypnic Jerks

  1. the more self-aware a person is and the more they are able to see things from another person’s perspective, the more likely they are to find yawning contagious

    Well hell, I must be damn self aware because I can’t keep myself from yawning. And I recently even yawned when a friend’s cat did.

    Maybe i just really really need to sleep.

    As for the déjà vu – I have trouble believing that saying hello to a colleague while filling my glass of water at the cooler (my last instance of DV) is an expression of repressed desires. Sorry Freud.

  2. “Have you ever woken up with a hypnic jerk?”

    Well, I’m not *quite* sure he was hypnic, but yes.

    (Thank you, thank you, ladies and gentlemen, I’m here all week. Try the prime rib.)

  3. I could barely read this blog post. The title had me yawn right through the first paragraph. By paragraph three I was yawning so much my eyes began to water! It was a relief to make it to paragraph four and discover –

    “that the more self-aware a person is and the more they are able to see things from another person’s perspective, the more likely they are to find yawning contagious.”

    BUT it made me wonder because I realized I don’t actually know that Mr. Me always makes me yawn and he is a very yawn-y fellow. Intrigued I read on and there was a potential key to my troubles-

    “One theory for contagious human yawning is that it’s a primitive response that used to help us communicate and coordinate sleep schedules”

    After a decade of interrupted sleep and restlessness my heart nearly broke when we decided to sleep apart last year. There were many tear filled partings as we each established our own nest and ultimately our own rhythms.

    I can’t say that we will re-unite by knowing that I perhaps I need to be more intune with his yawns-
    nor that I want to for, on the rare nights we spend together, I find myself awake much of the time waiting for morning . I will however be watching for my response to his yawns because the shift from bed partner to to visitor status was something I never in thirty years anticipated .

    Myoclonic twitches – who knew?
    I am bad for this , not that it is a problem but I have wondered about it.

    And truly – dejà vu I can’t recall the last time I had that feeling BUT I am old and I used to experience it often at one time.

    X-up you amaze and delight me – keep up the great postings!

  4. Edie has been complaining the past couple of nights that her head feels like it is floating into outer space and she has to grab it and reattach it to her body. Any research you have on this phenomenon would be appreciated (and somewhat comforting!)

  5. Isn’t brain function a wonderous thing? I have not only had those jerks but sometimes, I even vocalize (like a grunt) when I jerk myself awake. It’s embarrassing if you do it in the back of a classroom when you think no one is noticing you nod off. Then you have to pretend that you were clearing your throat and stretching at the same time. No one is fooled.

  6. “Have you ever woken up [from] a hypnic jerk?”

    Mine, or someone else’s?

    (This is my B joke, since Alison stole the obligatory one)

    I think I’ve mentioned this here before (déjà vu?), but I always get weird dreams when I sleep on my back.

    – RG>

  7. I was worried that a ‘hypnic jerk’ was just another thing I’m not cool enough to know. So, phew…

    I do that whole twitch thing usually when I’m really tired and trying to force myself to stay awake for some stupid reason, like finishing the end of a boring movie, not because I could be falling off a cliff. Now I feel kind of guilty for making my body think there was going to be some falling going on and all it was, was the end of some crap movie.

    I wonder if it could have something to do with an adrenaline surge? Because when you wake up like that sometimes your heart is racing and you feel kind of hyper-alert, like in a flight or fight scenario.

    Human physiology is an amazing thing!

  8. I went to a naturopath recently…she made me fill out a detailed questionnaire. One of the questions was whether I experienced hypnic jerks. I figured it was a symptom of a health problem. (?)

    Oh…and I find yawns contagious, experience hypnic jerks and I am open to the possibility that deja vus might have something to do with past lives.

    Anyone sneeze in bright sunlight? lol

  9. Jazz – Don’t be dissin’ Freud. He Da Man. Or something…yawn….
    Alison – Thanks for being the first one to run with that nice little set-up I left ya’ll.
    Jay – You talking about yawning is making me yawn. Your relationship is intriguing. As the revival of your blog!! Congratulations.
    Edie – She’s been getting into your peyote again.
    Julia – Yes! The brain is so odd and interesting and there’s so little we know about it. It’s probably up there in our heads every day laughing its ass off at us.
    Grouchy – Oddly enough, I don’t remember you saying that. I’m afraid to sleep on my back because I think I stop breathing when I sleep on my back.
    Kimberly – I don’t know if that’s the same thing as being in bed and experiencing a hypnic jerk. When you’re in a car or watching a movie or at work, nodding off you actually do fall – or at least your head falls over – when you doze off. That startles you because your body is not expecting its head to fall over when sleeping – it expects the head to be comfortably nestled somewhere. That’s what scares you and wakes you up and gets your heart racing. That’s what I think, anyway.
    MM – Photic sneeze reflex — sneezing in bright light. Very common apparently. Too bad I hadn’t written this post before you went to the naturopath. Did he/she explain what it was?

  10. XUP – that’s likely related. When you sleep on your back, you risk letting your tongue close off your throat. This is why the ‘recovery position’ in first aid is for the patient to be on his or her side.

    As for my dreams (since it’s not a repeat here), I sometimes half-wake up where I’m cognizant of my surroundings (e.g. bedroom) but unable to move. I dream that someone has broken into the house and I’m trying desperately to pretend that I’m still asleep so they don’t think I saw them (and therefore could identify them). But I also want to attack them, and can’t because of the paralysis.

    Then I wake up and notice I was sleeping on my back.

    – RG>

  11. How’s this for strange, I remember and experience deja vu around certain things. Specifically the colour orange. Anytime I’m doing something with certain shades of orange or visualize those shades in my head I can expect a deja vu experience in about a 3 minute window.

    I do the hypnic jerk thing when I’m trying to force myself to stay awake.

    And I yawn just thinking about yawning.

    Its all very cool.

  12. Yawning – I yawn when anything yawns. Yawning is a way to get more oxygen and I’m a very shallow breather, so maybe it reminds me to get more oxygen. It’s a good thing I never had the hungry hungry hippos game or I’d probably yawn myself to death.

    Hypnic jerk- I rarely get those. I had read they were the pent up electrical energy in your muscles bursting out when no longer needed. And by the time I go to bed, I am very relaxed, so, no pent up energy for me. (The only thing my body does to startle me awake is a weird hog-sounding snore.)

    Deja Vu- I get that way too often. But 80% of the time, instead of feeling like I did it before, I feel like I have dreamed it.

  13. Go Alison — good one!

    I have woke up with a jerk but didn’t have the sensation I was falling. My body just jerks like crazy and scares me awake. I hate that! I think my breathing slows down to next to nothing or maybe I even stop for a minute. Sleep apnea?

    As for yawning, I’ve noticed that I only yawn around certain people; weird. And, they never yawn back.

    And déjà vu — I get them quite often. Ahem… I believe that before we are born our soul maps out our lives. Déjà vu occurs in those moments of recognition that we are on the right path 🙂 #BelieveItOrNot

  14. I have bad sleep hygiene. I actually do watch a lot of movies and television in bed & that’s when I jerk. I’m pretty sure it is from trying to force myself to stay awake and thinking ‘I have to stay awake just a little longer’.

    And what kind of slacker do you think I am, I don’t fall asleep at work! LOL Of course, I work from home. 🙂

  15. Grouchy – Backsleeping is bad. It’s like dead. No other animal sleeps on its back. That’s because it’s bad.

    Mudmama – Orange, eh? Have you seen the Annoying Orange videos on YouTube? http://www.youtube.com/watch?v=ZN5PoW7_kdA That might cure you of that déjà vu orange thing.

    MM – Okay. Don’t forget to report back.

    Geewits – It’s all so bizarre. They can come up with speculation on why this stuff happens, but it seems like everyone experiences a bit differently and probably for different reasons too.

    Davina – Well, that’s as good an explanation of déjà vu as any, I suppose. I don’t believe it for a minute, but I won’t argue with you if you believe it. As for the yawning thing – I don’t think I’ve ever yawned in front of anybody that didn’t yawn back. That would be creepy.

    Kimberly – Why do you feel like you need to keep yourself aware if you’re tired and want to sleep?

  16. I mostly try to stay awake when I’m watching something interesting and I want to see the end of it. Recently, I was watching a documentary on something and trying so hard not to fall asleep, but it didn’t work I was out cold well before the end of the program. I don’t know why I don’t just DVR these things instead of trying to stay awake.

    You never try to stay awake when you’re tired like that?

  17. Kimberly – only if my daughter is insisting that I stay up with her to watch a movie or something (and it’s only 8:30) otherwise I just go to bed. Nothing is more important than sleep!!

  18. I hear that loud noise thing that wakes me up, but I always think I woke myself up snoring.

  19. Have you ever heard of the idea that memories could be inherited? It would mean that some deja vu could be actual memories from ancestors. I’m not sure about this, but when my mom went to Italy a number of years ago, she was HOME. Even though she had never been there before. It’s all so interesting for sure.

    And now I’m yawning, but definitely not from boredom!

  20. Cedar – It could be that, too!! lol

    Finola – I have heard something like that about gene memory. Also about tissue memory – that your memory doesn’t just house in your brain, but in all your tissues and organs and genes. They figured that out from people who’ve had transplants of some sort – organ, skin whatever – they often have memories of things that never happened to them, but which, apparently happened to the organ donor. (cue weird music)

  21. Hypnic Jerks. there’s a name for it. wonderful! I’d be wondering about if there were. been getting that a lot lately. almost asleep. woah, what? did one of those sleep sheep just ram me?

    what’s the use of being forewarned of pass the chianti. heh.