I've never seen someone misinterpret a hand pointing in the direction a person wants to go. It's about as basic as you get. Even dogs understand. But my wife and friends started noticing people who have issues with the L-shaped right-turn signal. They know they have to use some kind of kink in their arm and raise it up but just can't seem to get it right. And they use it despite there being a perfectly good alternative.
We can blame this all on our obsession with automobiles. I'll explain.