Too big to laugh

We used to read the book "Duck in the Truck" endlessly for Jacob but haven't read it in quite some time. This afternoon, he found it amongst all his stories and wanted me to read it with him. He always used to laugh at the ending of the book. When I was about to turn the last page, I was excited to hear his sweet laugh but it didn't come. He sat, just looking at the book...no laugh, no twinkle in his eye, nothing. I asked him why he didn't laugh and he simply said: I'm big now mom, I only laugh at this silly book when I'm a baby.

Sigh...he's growing up too fast.