[vidarh]

You will often find authors talking about characters "telling them" what they do, and while some means that metaphorically, if you dig into it you'll find a lot of people who mean it literally. Not (usually) in the sense that they believe this is some separate entity, but that they do often have the characters story play out with varying fidelity of both visual and aural presence in their mind.

A surprising number of people also have e.g. multiple voices speaking in their minds (again, the distinction between mental illnesses causing people to have intrusive voices they believe to be other entities vs "just" seeing them as thoughts/imagination playing out)