I didnt really think about this before but after talking to some people close to me Iv come across something interesting.
Some people dont have internal dialogue, they dont think in there head. they either literally talk out loud or just impulsively go threw actions that have become routine.
for me, its my internal dialogue that helps me question and critically analyze things. im always thinking about things, working stuff out in my head.
even as I'm writing this i have a voice (mine as i perceive it) basically narrating different versions of what I'm going post in my head like how to properly word it, what i should say, how it may be perceived ect.
its strange for me to think that others dont do this.
where do you think thoughts come from? and what about "intrusive thoughts"? have you ever had a thought that clearly wasn't your own? like something completely ridicules and morally out of character pops into your head, something you know you wouldn't do but the thoughts just manifests itself anyway?
I've given a great deal of thought to such things.
Consider this: why does internal dialogue need to be in one's spoken language? By limiting our thinking process to the rules and conventions of speech and language, are we not encumbering, hampering, and impeding our minds?
That's why I like to occasionally practice quiet minded meditation. It's not a formalized system, but the formal systems that it is based on are Eckhart Tolle's "Practicing the Power of Now" and pranayama (yogic meditation that focuses on breathing).
FYI, I am Christian, and intrusive thoughts sometimes need to be dealt with by invoking the name of Jesus and seeking His intervention (never fails, for me, anyway, but obviously your mileage will vary according to your faith).