Thanks for your thoughts everyone!

I'm glad to hear that he's not the only one who's experienced this. It does sound like it happens more when he's doing something not too exciting (like putting on shoes, or other similar tasks). Perhaps it is his brain just working overtime...

I did a bit of googling about children's inner voices and children hearing voices - sounds like it's quite common and usually nothing to worry about (unless the voices say distressing things).

I'll talk to him a bit more and try to find out when this is happening, what his 'narrator' is saying, and so on.
CoastalMom - it's a good point about noticing vs not noticing this is happening. Perhaps if he accepts it's nothing to worry about, he can just let it fade into the background, or figure out how to turn it of...


I did find some interesting links on theories of child development and learning by Vygotsky, eg:

Inner speech in general is thought to be useful and helps children learn (see Vygotsky)

http://www.simplypsychology.org/vygotsky.html

http://en.wikipedia.org/wiki/Private_speech