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”?