Non-mobile individuals living in a community undergoing a linguistic change usually display a pattern of variation where citation styles are more advanced than naturalistic styles with respect to the change in progress. This suggests that speakers' intentions or norms, while they may shift only gradually, can do so more easily than their productions. Two groups of 'mobile' speakers—adults who grew up in one dialect area and moved to another, and children who acquired one dialect at home and another in the community—showed the opposite pattern: spontaneous speech approximated the dialect of the second community more closely than did word-list productions. Analysis of these speakers' low back vowels (the LOT and THOUGHT word classes) also suggest that most adults can at least partially learn a vowel distinction as well as a merger, though children are able to do both things more quickly and completely.
Johnson, Daniel Ezra and Nycz, Jennifer
"Partial Mergers and Near-Distinctions: Stylistic Layering in Dialect Acquisition,"
University of Pennsylvania Working Papers in Linguistics:
2, Article 13.
Available at: http://repository.upenn.edu/pwpl/vol21/iss2/13