Oh the box isn't so black. That's not to say that everything
will make sense but consider:
a) We're communicating
b) We have generalized knowledge of patterns observable through
behavior.
Yes, there is lying. Yes, many of the methods used to
"mind-read" fail. In fact, I say it frequently:
MINDREADING IS IMPOSSIBLE
But... you _can_ understand them and have a seat and look around
their house, once you understand their own patterns.
That's not to say they won't surprise you but up to a limited
point, it's certainly possible. And the more patterned someone
is, the easier it is to step in their mind. Might not see
everything but you can see a lot.