premise: It is quite firm about the r -sound when it follows a vowel-sound or is at the ends of words , not dropping it as is usual with the RP but insisting that it be given full value , in various ways , as it is in Scots and Irish and , generally but not always , in the speech of most Americans except for those in New England and the South .
hypothesis: Many Americans whose roots ile in Ireland or Scotland still have some of the same speech patterns as their ancestors .