OK, this is interesting.
From the User’s Guide to the Brain by John Ratey:
If you want to verify the lateralization concept [of language dominance in the brain hemispheres] for yourself, take this test: Try to repeat a passage of poetry while you simultaneously tap a finger on the table. It is significantly more difficult to tap a finger on your right hand than your left, because the movement of the right finger is controlled by the left hemisphere and competes for neurons with the language areas there. The brain is not limitless. If you found the reverse, you may be one of the few people whose right hemisphere dominates language. If you can tap fingers on both hands equally well, you may be linguistically ambidextrous.
I had a shot at this under my breath, tapping fingers on my knees because I was in my favorite reading chair and there was a math tutoring session going on at the nearest table. I used my own poem, the one from my bouquet of love lyrics that starts out “Be damned and double damned, you cur…” Sonofagun if I didn’t blank on some of the words around the second line while I was tapping my left forefinger. I tried the right. Everything rolled out. Went through the sequence again. Same result. Not dramatic, not a total block, but it was easy tapping on the right, just a bit of work on the left, like speaking your own language versus your fourth year of foreign language in high school.
Apparently my brain is on backwards. Who knew?
This is even more interesting because although I am a kinetic bastard — ask anyone in the gym — I am also a klutz who can trip over a chalk line on the sidewalk and have all the grace of an intoxicated wolverine. There is some information enfolded here about language crowding into every crevice and interstice of my Mercury-intoxicated brain* and crowding out motor fluency, if I can figure it out.
Try it and see how your mileage varies.
*The Olympian patron of language, not the heavy metal. I deplore heavy metal.