It has been done.

Landon was in his highchair, stuffed full of breakfast goodness. I asked him "Do you want to get out?" and he shook his head firmly, NO! I thought, he probably doesn't have a clue as to what his head shake is, let alone that it means something. I go to get him out and he starts screaming at me. So I put him back down, and he's fine.

Ladies and gentlemen we have a concept of yes and no! Who'da thought?! Apparently 16.5 months is the month for understanding, this is good!