Schilling-Estes, Natalie. “On the nature of isolated and post-isolated dialects: Innovation, variation and differentiation.” Journal of Sociolinguistics 6.1 (2002): 64-85.
The author compares the language varieties spoken in Smith Island, Maryland with Lumbee language, showing that isolated communities are not necessarily conservative and homogenous in their language. She briefly describes each isolated community, then discusses various meanings of the concept of isolation. The features of Lumbee English and of four generations of speakers are discussed on pages 73-76. Figure 5 shows percentages of /ay/ among Lumbee speakers in each of the four generations of speakers. Figure 6 shows percentages of r-lessness among Lumbee speakers by birth year, from 1870-1990. The author discusses the innovative [a>^I] feature, explaining that it appeared in Generations A and B but was then replaced by the more common Southern monophthongal variant during Generation C (people born 1939-1952). Interestingly, the innovative pronunciation was most heavily used in Prospect (the most isolated Lumbee community) during a period when most Lumbee were quite isolated.
The author concludes with an exploration of “reasons for the Lumbees' decreasing intra- and intercommunity distinctiveness vis-à-vis the increasing dialectal distinctiveness of Smith Island” (p. 78). Her reasons relate to the amount of contact with the outside world, type of contact, community size, sense of in-group identity, and the group's perception of the permeability of the linguistic as well as non-linguistic boundaries separating it from outsiders.