Hello, I am a FTM to an 18 month old boy. He says single words, he knows about 20 different words or so. When I ask him to say a word, or what is this called, or to show me something (that I know he knows) he won't. A lot of times he will look at me and nod no with his head after i ask him something. I've tried it 1st thing when he's woken up, after i feed him, during play. I'm not sure why he's saying no to me. I'm wondering if this is normal and if anyone has suggestions or recommendations with books, or practitioners i can look to talk to about this. I appreciate your help!