[eavc]

I've recently wondered if shaking the head to signify disagreement or refusal stems from that being an effective way for a child to refuse food it doesn't want. My son shakes his head almost reflexively, and it makes it very hard to feed him something he doesn't want.

[gbog]

Probably not. When I was in Nepal, I noted shaking head left and right means "yes". And "no" is done with the hand open, rolling it on the axis of the arm ("couci-couça" in French).

BTW Children are sponges, they copy you. For instance my wife and I do not like that much fruits, and our kid don't either, which is sad.