That voice in his head

A conversation with Maddox while washing dishes together:
Hugs me and says: This is my friend Mommy. See, I'm gonna say it. [closes his lips tightly and looks like he's thinking really hard]
Me: what did you just do?
Him: I said it; didn't you hear it?
Me: Are you saying it in your head?
Him: Yeah, not in my mouth.