In fact, to go further, although I don't believe we are "blank
  slates" per se, we just may be composites of every person who
  ever talked to us, whether in person or through TV or song,
  chopped up and reformed and recombined in a unique fashion. The
  inner monologue is often "voices from the past" anyway;
  sometimes it's easy to identify who (Mom, Dad, 7th Grade Coach,
  3rd grade teacher, mean Aunt) - and sometimes it becomes such a
  part of a mental/subvocal process that we use regularly, it
  becomes us entirely.

  So I think we can tell via personality. We *do* have a two good
  "anticipation machines", one that does quick assessments
  (prejudice/assumptions/emotional/amygdala) - and a much slower
  assessment, given time to reflect (pre-frontal cortex, rational)
  etc - the amygdala gets first and final say of course (as the
  pre-frontal cortex computes but the "push" seems to be
  emotional/amygdala based).

  I think that's how we could know. Whether we *would* know....
  well, that might have to do with our suseptibility to influence;
  some of the trust factors that you've been working on and such.

  "Do I trust myself completely or am I capable of things that I
  am not yet aware of?"

  It's funny; we still stigmatize "voices in the head" and yet -
  to some degree, we all have them. Different "me's" all in a
  crowded little space.