Inner Voices

Those inner voices - what are they? How do we relate to them? How do they relate to us? What
kind of existence do they have, if any?

By inner voices I mean those quasi-collections of thoughts and emotions that act as representations of 'Significant Others' in our mind. Those we consult with, those who tell use to do this and not that, those who we imagine what they'd say and think about our choice of clothes. I'm not talking about a modern Jiminy Cricket or a Freudian super-ego, nor the detached voices that often plague a schizophrenia patient. Those voices represent others who we care about but they do so by being a part of ourselves, by being our own creation. They are an integral part of the human way to internalize others (and so play a pivotal social and ethical role within us) while also manifesting and testing desires and thoughts of our own (thus enhancing our creativity, our sense of order and our cohesive-seeming Self). Sometimes, they show that we are not alone in the dark.

But how is this phenomenon called? Why do some people get 'internalize' and not others? Are all
the representations the same (in essence, power, function, internalization status)? Where do they
fit in in relation to our 'own' internal monologue, our own main 'Stream of Consciousness'?

I'm looking for some answers.