I'm convinced this isn't actually a thing for most people, but people mix up thinking with the translation of thought into words.
Its not for everything. It's mostly for intellectual tasks or planning. Eg Trying to solve a programming problem, or remember the list of items are needed for dinner while shopping. Personally I reason "out loud" in my head while doing those things, some people don't.
Though, also, I think that the internal monologue is maybe less an aspect of how we think, and more an aspect of how we remember. I haven't looked into it, but my feeling is that a more active internal monologue might be correlated with someone who has an easier time remembering sounds than, say, images.
It doesn't have to mean that every action is accompanied by a monologue, a task like tying laces can be done with no active thought about the specific movements.
Take the top lace under the cross and through the hole.
Make a loop in one lace.
Wrap the other lace around the loop and push some lace through the hole that is made at the bottom to make a second loop.
Pull both loops tight.
Usually it's packaged in a story about rabbits.
It's like the minds-eye or "hearing music", I can do those but only if I intentionally need them.
I talk to myself to find good ways to express a thought with language, but not to think.
> Or written in a journal?
I do this to remember and sometimes to prompt thinking, but writing isn't the thinking. It's the outcome of it.
Do I just have a narrower definition of reasoning?
The reason I'm interested in this is because I have a very low verbal IQ but a relatively high spatial IQ. I have often wondered if this divergence is because I don't reason with language, or perhaps what I experience is normal but I just disagree about the semantics of reasoning. Unlike some people, I can do internal monologues, I just have no idea what people mean when they describe that as reasoning.
For example, if you're trying to work out why some electrics aren't working, do you say in your head, "I should check the fuse box" or do you just visualise the system and components that need checking? I do the latter, and words would only enter my head if I need to write that down or say it to someone else. Furthermore, I don't even understand how you can monolog in your head about something prior to thinking it. This concept makes no sense to me and would be an alien form of reasoning to me if people can do this.