This is a sort of silly question but it has been going on for a while now but I am just curious if anyone else's kid does this. My four year old spends quite a bit of time thinking. Like thinking is its own activity. It takes two forms. One is a sort of pacing/skipping in a circuit around the room or yard while thinking and the other is a lying around thinking. He doesn't talk to himself while he does it. He is always able to articulate what topic he is considering if I interrupt to ask. He isn't sad. He actually seems happy to get lost in his own head. It is just that lately I will ask "Do you want to (insert activity)?" and he'll respond "no thanks, I just want to think" and off he'll go.

Yes. DS6 does this all the time and it can be quite disconcerting when you're in the middle of something completely unrelated and he suddenly has to share whatever observation/conclusion/factoid he has come up with in his head.

I wish my DS would think inside his head more. My DS5 loves to ponder but needs to talk outloud to process it....ad nauseam. His kindergarten teacher is going to LOVE him.