Question

Why does nodding of the head signify Yes and shaking of the head No?

Answer 1

Answer:

It's simply "human nature".

Answer 2

Answer:

Shaking the head usually indicates confusion or lack of comprehension. In several nearby countries like Greece and Albania, shaking one's head can actually mean yes. As to countries which practice the usual nod/shake arrangement, nodding likely originated as an informal bow.

Explanation: