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It would be much easier to adopt a poker face if we were in control.
I really admire people with the ability to go all poker face.
Mine is said by friends to be transparently readable and the kids are always telling me what kind of face I've got on: the thin-lipped Angry Mum face, the oh-look-she's-going-to-blub movie face, the warning, headache approaching, frowny face, the soppy mummy smile.
Most of us might think we do a good job of keeping our feelings under facial wraps.
But I've been thinking about just how much of what our bodies express is almost absolutely involuntary. What's with blinking, for a start?
Why would our bodies require us to droop bits of skin over our eyeballs every few seconds?
And why is blinking so easy and natural (until you start thinking about it) and winking so blooming tricky? If I was in charge of human product development, I'd give us something really cool and space age like revolving eyeballs instead, that lubricated themselves by rolling back into our heads. Or not.
Because that would mess with a function whereby we actually have a little brain shut-off every time our eyes close for a blink.
Researchers worked this out by inserting blank frames into a Mr Bean video people were watching.
I hope they checked that their researchees weren't the highly evolved kind of people who switch off when they see Mr Bean anyway. And how about yawning?
Did you yawn when you read the word yawning? I yawned when I wrote it ... and when I wrote all those other yawns of explanation, too.
We all know yawning's catching. You might've just caught it off a word, for goodness sake. And it's a widespread catchment to catch on to, this yawning business. Apparently all vertebrates do it. Yep, if you've got a backbone, you yawn.
Even if you're a fish or a foetus. Although, weirdly, only chimps, dogs and humans over the age of four seem to find yawning catching.
That useful information was probably brought to the world by someone paid a stonkingly large research grant, so I might at least try to glean some value from it by passing it on to you.
And isn't it interesting to consider that humans, chimps and dogs are thought to be among the most empathetic of animals, thus giving rise to a theory that we actually open our mouths, drop our jaws and inhale a whole lot, not just out of boredom, or tiredness, but out of a deep natural understanding of each other.
OK. I'm sick of yawning now, so I'll move on to my most notable involuntary reaction of the moment. What Darwin called ''the most peculiar and most human of all expressions''.
The science says something about capillaries opening in your cheeks and all the blood rushing there: because your feet can't or won't move, your face does all that fight/flight instinct stuff instead.
Never mind that I feel like a beetroot-marinaded lobster, I've read that the majority of people subconsciously find those who blush to be more attractive and trustworthy.
Think blushing bride. Blush of youth. And as for the trust, it seems we like to be able to read implied guilt so clearly in people's faces. Blushability does not make for good poker-face physiology.
Incidentally, I am not sure if Darwin ever wrote about the pink Amazon River dolphin, which lives in rivers in the Amazon and, yes, blushes pink when embarrassed or aroused.
Overactive sympathetic nervous systems, those pink dolphins. All of them. Sneezing. Or sternutation, to give it its medical name.
Now that has something to do with the parasympathetic nervous system, which, instead of controlling your fighty, flighty blushy bits, is into helping you rest, digest and be all balanced. So sneezing is a reflex to help you reset your snuffly bits.
And get this: known sneeze triggers, as well as all that cold and allergy malarkey, include sunlight and sex.
An estimated 18% to 35% of the population have a photic sneeze reflex (the sunlight one) and there are no reliable percentages that I can find regarding sexually induced sneezing but it's a scientific phenomenon first noted in the 1890s, so who am I to dispute it?
Laughter is my favourite thing to do with my face, but it's not strictly involuntary unless you've got involuntary emotional expression disorder.
Still, I bet some scientist somewhere has coined an orderly disorder name for that brilliant thing where you laugh till you cry and when you try to explain, everything just gets funnier and more lame.
Extreme emotional enjoyment disorder, perhaps?
The very antithesis to poker face.