I'm going to talk about daydreaming. But I want to point out that there is no visual aspect in what I am describing. It is all audible. The people in my daydream talk back, but I never confuse their words for being audible. Many times I am talking out loud to myself (I do not make voices for other people in the daydream), other times I am having the conversation in my mind. Thoughts are always in conversational form.
It begins instinctually never consciously. Sometimes I don't even realize I am doing it until I'm half way through a daydream. I will continue even after I am consciously aware of what is going on.
I very rarely speak out loud when others are in the room, although I will go through the daydream internally in the presence of others. Sometimes my lips are moving, but if I notice I consciously stop them from moving and continue on my daydream.
I want to describe how and when this occurs.
When I'm learning something I consume information. I think about the information I'm reading and try to form an understanding of it. When I feel I have grasped the information I generally go into daydream mode. The daydream will generally consist of me having a conversation with someone, or a group of people. In the daydream I assume the role of an expert even though I just learned the information.
Before certain events I do the same thing where I daydream an entire scenario before I encounter it. Say I'm going on a job interview. I will enter a daydream where I am interacting with the person having the interview. When I was younger I remember doing this before I would ask a girl. Often times unconsciously I feel this internal interaction is enough and I never actually follow through with the experience.
When I am watching something like a movie, the news, or reading a fiction book. I may go into daydream mode and relive the scene. If it was something like the news I will daydream that I am in a position of power where I can actually make a change. Again it is conversational form, perhaps I'm giving a press conference or perhaps I'm sitting with other government officials and I am telling them what I want to happen.
I can continue but I think you have gotten the point by now. What function(s) are being used here? Or does this go far beyond function theory?