Shaking His Head is the New Black

You know how sometimes a trend catches on, and within about a month people are doing it but have no idea why, or what the original connotation of the trend was?  That's Nicholas with shaking his head "no."  He's figured it out in the last few weeks, to the point where it became, for a short time, an effective method of communication.

"Nicholas, do you want more milk?"

[ Vigorous head-shaking. ]

But then he got a little too impressed with his ability to do so, and we have ended up with several conversations like this:

"Nicholas, do you want another cracker?"

[ Vigorous head-shaking. ]

"Okay."

[ Whimpering and reaching for the cracker.]

He'll figure it out eventually, of course, but for the moment it's a little frustrating that he learned something so effectively that it's no longer effective.  Sarah thinks this is what the terrible twos are like.  I'm assuming it'll be worse because by the time he turns 2 he'll know that he's saying no and being difficult, where right now, I still get the sense from him that he's trying to communicate honestly (for the most part) and just having trouble expressing himself in ways that are mutually agreeable and comprehensible.