This paper considers the relative influence of the family and peer group on an individual’s grammar in a comparison of three female undergraduates at the University of Pennsylvania. Automatic vowel measurement is used to assess the degree of participation of these young women and their families in the local phonology. While each woman’s vowel system contains less markedly Philadelphian features than her family members’, in no case is there an abrupt jump from the Philadelphia system to an unmarked system. We therefore conclude that the phonological reorganization in progress in Philadelphia, specifically the emergence of the nasal short-a system, is accomplished via an intermediate weak-system stage.