I wonder when one learns a second language has anything to do with some of this stuff. I have a feeling somebody that learns a second language later in life has a lot tougher time thinking in that second language without translating in their head than somebody that learns a second language as a young child or even along side their primary language their entire life.
I've heard a theory that people are all born with perfect pitch and they gradually lose it by the time they're 5. That explains the fact that people don't have accents in their mother tongues, but do in languages learned after age 5.