Ooh, it never occured to me to wonder about that, but it's a poser.

I'm guessing it's due to the same thing I experience in karate class when I face someone and they're supposed to punch me, only I can never figure out which is their right and which is their left, because their right is on my left and vice versa.

I finally gave up, and now I just point. "Punch me with that arm, whichever it is."

DebBee