Fun With Neural Pathways

Try this:

1. Lift your right foot off the floor and move it continuously in clockwise circles.

2. While continuing to rotate your right foot, raise your right hand and draw the number 6 in the air.

If you write the number six, your foot will change directions no matter how hard you try to resist.

Now, rotate your left foot clockwise while writing the number 6 in the air with your right hand. You should be able to do both simultaneously with little effort.

So, what gives?

It's probably the case that the neural pathways directing limb rotation on the same side of the body share a common brainstem/spinal pathway. Thus, writing the number 6 (a counterclockwise movement) while making a clockwise rotation of the same-side foot is impossible. The shared neural pathway can't carry conflicting instructions.  But if you try to do this with right and left foot, or left hand and right foot, the impossible task becomes easy because you're using two different pathways to carry the opposing rotational signals.

Comments

[Pierre Corneille]

I had trouble doing it with my left foot/right hand, too, although not as much as with my right food /right hand. Does it matter that I'm left-handed?

[Dr X]

Good question. I don't think so, but can't say for sure.

[Johnny Au Gratin]

I find this sort of thing fascinating. I was unable to do it the conventional way, but hit on the idea of drawing the six by starting at the loop join and moving my hand in a clockwise spiral to make the same shape.

As a musician who mainly plays stringed instruments, I wonder if something like this could explain why when my two hands are performing the largely different tasks of picking or bowing with the right hand, and fretting or intonating with the left it comes very naturally to me. But playing separate left and right hand parts on a piano where the actions quite similar (mainly reversed) is much more difficult in my experience.

[Dr X]

"Easy" is evidently an overstatement. It would be more correct to say "can" or "possible" (versus impossible).