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April 15, 2009 6:28 PM   Subscribe

Why do my hands mirror each other's movements?

Something I've wondered my whole life, and that some anatomically savvy MeFite might be able to explain: moving one of my hands (say, making a fist or moving my thumb around in a circular motion, or writing with a pen) causes the other hand to make sympathetic movements (more like twitches of the corresponding muscles than exact copies of the other hand's motion). They aren't noticeable if I'm using both my hands to do something, but if one hand is at rest, it's obvious. It seems to be stronger one way than the other. My mother's hands do this too. Why?
posted by ocherdraco to Grab Bag (14 answers total) 2 users marked this as a favorite
Best answer: I think the term you want is "mirror movement." My hands do this to an extremely large degree, right mirroring left, but I have spastic cerebral palsy affecting my right side, and so for me it's kind of expected. I don't know if it's expected for the rest of you, though.

There doesn't seem to be much on the internet about it that I can find, but the first page of this article lists several conditions it is associated with, if that helps.
posted by sineala at 6:50 PM on April 15, 2009

I have this too, but I have a syndrome that corresponds with it (it's highly unlikely you have it; it's really rare).
posted by desjardins at 7:09 PM on April 15, 2009

Response by poster: Fascinating. It never occurred to me that it might be a symptom of something. I wonder if in my case it's more akin to being double-jointed: it's own thing, rather than connected to something larger.
posted by ocherdraco at 7:20 PM on April 15, 2009

Response by poster: Argh. I'm a book editor and I can't even punctuate "its" properly.
posted by ocherdraco at 7:30 PM on April 15, 2009

There is a condition called "mirror movement disorder" or maybe "mirror dystonia" that appears to explain your symptoms but nothing larger - it's hard to find any information online about it for some reason, though.
posted by mmoncur at 7:45 PM on April 15, 2009

I wonder how many people have this on a regular basis. I only get it when I'm doing something that requires intense concentration-- for example, I'm irritatingly right-handed and trying to correct that. So recently I've been brushing my teeth with my left hand. Whenever I do, my right hand gets into the act as well (muscles contract, sometime even the hand makes brushing motions). If I try to prevent the right hand from moving, my left hand can't figure out how to do the brushing.

Interesting article, sineala (seems to say I'm normal, which in this respect is expected).
posted by nat at 7:56 PM on April 15, 2009

are you left handed by chance? were you "forced" to use your right hand as a child? just a thought.
posted by desjardins at 8:31 PM on April 15, 2009 [1 favorite]

Response by poster: Nope. Right-handed.
posted by ocherdraco at 8:50 PM on April 15, 2009

I have worked as a personal trainer for a number of years. And I remember one client who had what you're describing. Gave him a dumbbell, and both hands grasped simultaneously, the empty hand doing a sort of smaller, echo of the hand with the weight in it.

Normal, healthy, fit guy. Just had a body quirk.
So casting my vote for: it's normal. don't worry about it.

The geek in me wonders though, if you've tracked the degree to which it happens for you- more when you're tired, stressed, focused on learning something new? My guy usually exhibited it more on new exercises, part of the learning process?
posted by SaharaRose at 9:44 PM on April 15, 2009

Response by poster: It doesn't seem to differ with those factors. But it does require specific movements—they don't mimic everything. I imagine this is because only certain muscles (or the nerves leading to those muscles, or the part of my brain responsible for those muscles) are affected.
posted by ocherdraco at 10:16 PM on April 15, 2009

posted by knile at 9:23 AM on April 16, 2009

Errr, sorry, ignore that link. I didn't fully read the question.
posted by knile at 9:24 AM on April 16, 2009

IANAD or any relevant type of professional, but perhaps practicing some sort of dancing or other rhythmic bodily movements where hands and arms do different things might help to retain the muscles and nerve connections. There are a lot of forms of dance where one hand follows the other and then vice versa, etc.

Certain sports might have the same effect
posted by jameslavelle3 at 10:41 AM on April 16, 2009

People become acutely aware of this phenomenon when they begin to play the piano, which naturally requires that you learn to do two completely different things with each hand.

I was teaching my student yesterday how to train his brain to dissociate the two hands. I use a snapping exercise - one hand snaps a triplet (waltzlike) rhythm while the other one snaps a straight one-two-one-two. The rhythm combination is called "polyrhythm" and is used frequently in music, which is where I first encountered the need for it. It's all very rub-your-tummy-and-pat-your-head, which is to say that your brain prefers simple things, and telling both of your pinkies to move identically is easier and is therefore its default setting. Can be overcome for most people though.
posted by greekphilosophy at 11:35 AM on April 17, 2009 [1 favorite]

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