Published online by Cambridge University Press: 29 April 2014
A number of studies of African American communities show a tendency to approximate the phonological patterns of the surrounding mainstream white community. An analysis of the vowel systems of 36 African American speakers in the Philadelphia Neighborhood Corpus compares their development over the 20th century with that of the mainstream community. For vowels involved in change in the white community, African Americans show very different patterns, often moving in opposite directions. The traditional split of short-a words into tense and lax categories is a more fine-grained measure of dialect relations. The degree of participation by African Americans is described by measures of bimodality, which are applied as well to the innovative nasal short-a system. The prototypical African American speakers show no bimodality in either measure, recombining the traditional tense and lax categories into a single short-a in lower mid, nonperipheral position. The lack of relation between the two short-a systems is related to the high degree of residential segregation, in that linguistic contact is largely diffusion among adults rather than the faithful transmission found among children.