Maybe

Why do we only have head movements for yes and no? Why isn't there a head movement for maybe?

My answer to a lot of questions is maybe.

"Hey, would you save me if I was drowning?"

"Maybe." But instead of taking the time to say maybe, my head could move from the top right to the bottom left.

Maybe not could be from the top left to the bottom right.

"Are you saying you wouldn't save me?"

To that question I would move my head around in a frantic circle, meaning I need more clarification.

"Well, how cold is the water?"

"You want to know how cold the water is when I'm drowning?"

"No sense in both of us drowning."

This actually happened to me once, but when I asked my friend if he wanted me to save him, I couldn't tell if his head was saying yes, no, or maybe.