ABSTRACT
This chapter considers the aspects of longitudinal studies by examining the dynamic status of African American Language (AAL), a variety that has been subjected to a full range of analyses covering many variables and speech communities. It argues that understanding the trajectory of language change over the lifespan can be very effectively described by using composite indices, rather than focusing on individual linguistic variables in isolation from each other. The chapter illustrates how longitudinal data collection can be facilitated via cross-disciplinary collaboration. It describes how a composite index, namely the Dialect Density Measure (DDM), has been used to assess the development of AAL across the lifespans of the many African American children. DDM trajectory analysis allows answering the question of when the minimal and optimal times for vernacular AAL usage are likely to be. Statistical smoothing of these trajectory trend lines results in the overall roller coaster pattern exhibited in the chapter.
