Here’s an interesting experiment I would like to see.  Look at adults who learned a second language as a child from one of their parents.  For example, the father speaks only English but the mother speaks English and Hungarian.  English is the standard language outside of the home.

Profile the personalities of the parents.  Now have a Hungarian speaker interview the subject and profile his personality and separately have an English speaker profile the subject’s personality.  Is the subject’s personality different in the two languages and is he more like his mother when speaking Hungarian?