Fill in the blank

A normal evening goodnight ritual consists of reading a story, singing and song and praying together. Silas has been able to point to objects in his "Bunny book" and say what they are for awhile now.  He especially likes the word "toadstool" and if you take a break at the end of the sentence, he will put the word in just where it should be.  The other night we were reading "Goodnight Moon" for the 52nd time and wanted to try something out. I stopped just before the last word on every page, and waited before saying the last word.  To my suprise I never got to say the last word, as Silas was busy filling in the blanks.  He was saying words I didn't know he knew...mush, hush, chairs, tree, air....etc, etc.  He could fill in the blank to every single last word of every single page. I guess Silas does have the ability to listen, even though he is squirming around like crazy!