Imagination it turns out is a great deal like reporting in your own head. Here is a paradox of fiction-writing. You are crafting something from nothing which means in one sense that none of it is true. Yet in the writing and perhaps in the reading some of a character's actions or lines are truer than others.
I align myself with almost all researchers in assuming that anything we do is a composite of whatever genetic limitations were given to us by our parents and whatever kinds of environmental opportunities are available.