I’ve seen people playing video games (X-Box, etc) get really, physically into it. Hell, when I play a simple game on my Palm, I twitch quite a bit. But I don’t play any of those “serious” games. 
My question is; why? What do we hope to accomplish by expending all that energy? Few of these games have any real tactile feedback. Pushing harder on the “fire” button gets you nothing. Tilting the controller doesn’t either.
But try to not do it.
So, is it some kind of instinctual thing?
No tactile feedback (unless you’re using one of those vibration controllers or a PainStation) but plenty of visuals. I get motion-sickness if I play First Person Shooters for too long. Particularly the one where you bobbed up and down as you ran. oooOOOOoooooh. 
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I love watching the facial expressions of some who is juggling. 
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I think you meant ‘body language’ and ‘instinctive’.
But anyway, when I play video games, especially driving games or ones involving leaping and ducking, I often mimic the moves as they happen without thinking about it, and also will try to get extra oomph out of my joystick by moving my arms in various directions, even though all it needs is a gentle touch to achieve it.
I think we just get deeply involved in the action of the game.
In some games, it does. Hooray for analog controllers!
Actually, “Body English” is a specific term used in sports to describe the various contortions a player makes when willing a ball to go in a certain direction. “Instinctual” is also a perfectly good word, if less commonly used than “instinctive.”
Oh. I stand corrected.
But it sure sounds weird to my ears.
Nyah, nyah.
Yeah, in sports too. Ever watch a bunch of guys play bocci ball? That’s exactly what I mean. We know our actions will have absolutely no effect, but we do it anyway. In all cultures that I’ve observed.
I want to know why. Scientifically. We must expect, deep in our primitive brain, some result. Maybe human psychokinetic powers were once stronger than they are now. Throw a spear at a mastodon and then guide it to it’s target.
SPOOFE already mentioned it: I have a PS2, and ALL of the controls are analog. This can make for an intense and physical gaming experience.
because the human brain hasnt evolved to play computer games. As far as the brain is concerned, you ARE that skater.
I have also noticed that whenever you are feeding someone else, you instinctively open your mouth. Even when you are aware of it, its incredibly hard to stop.
A hundred million years ago when I was playing Descent II, a 3-D, first person game in which you’re piloting a ship in all three dimensions, I noticed that whenever I would, say, turn the ship right I would also turn my head to the right, eyes still locked on the screen. In fact, every time I turned the ship I would turn my head to match, even though my monitor wasn’t going anywhere.
Even if I were actually piloting a ship, I wouldn’t need to turn my head when I turned the ship – my view would swing around with the ship itself. Go figure.
Me and the mrs both looks like complete fools playing Tomb Raider. We keep craning our necks trying to “look around the corner”.
I think that’s probably it, Shalmanese. Kewl 
Yea, I was playing Apex and I kept tilting my body (and the controller) while trying to get around turns, swearing the whole time.
There’s even a word for it in the gaming industry: Immersion.
For me, it definitely depends on the game. I find myself doing it in some games, and not in others.
Hehe…I used to play CounterStrike, and when someone would come up behind me (in real life) I’d spin around in the game and be utterly confused when nobody was there. I’d stop firing, too, cause I didn’t want to “shoot” them 
Anyway, it usually took me a few seconds to realize that there was actually someone behind me. Sad, really…
There was a time in my life I felt strange going through doors simply because I didn’t have a grenade to throw through ahead of me.
I found after long CS sessions, I’d go into rooms like I would in CS. You know, slip in the door, sweep the room, hug the wall to get to the next door.
I find myself fully expecting to be able to select “undo” then getting really angry when I realize my botched (for example) shave is going to look goofy until the hair grows back. Always after a long session of word processing or Photshop.
Save states are the worst. After hours playing games with the auto save/auto load feature you start to do it in game without thinking.
Then IRL you start trying to do it, for example, I was playing pool and I didn’t like my chances of getting a shot. So I thought, hey, no big deal, I’ll just save here and load if it doesn’t work. I then went for the auto save button, quickly realizing there was no keyboard infront of me. I was just glad I was the only one who knew why my hand suddenly jerked out when I was lining up a pool shot.