Abstract
<jats:p> Sociolinguistics and socio‐historical linguistics make clear and testable predictions about the linguistic behavior of the individual speaker across the lifespan. While Sankoff and Blondeau's (2007) call to action has resulted in a wealth of small‐scale panel studies, the dearth of large longitudinal data‐sets means that we continue to know very little about the range of linguistic lability past adolescence and about the factors that condition changes in adult speakers' linguistic habits. This chapter explores intra‐speaker lability on the basis of a novel corpus that spans the entire adult life‐course. We first address some key theoretical and conceptual issues related to language acquisition and intra‐speaker malleability. We then report on three empirical studies that probe the degree and the conditioning factors of linguistic (in)stability in the individual. The chapter focuses on intra‐speaker malleability during (i) age‐grading (the regular association of vernacular forms with certain portions of the lifespan, such as adolescence or old age), as well as (ii) changes in progress (the shifting of a speech community toward incoming forms in real time). We reflect on the implications of our findings and conclude that the language sciences need to work toward a better understanding of our linguistic abilities across the <jats:italic>entire</jats:italic> life‐course, including the later life stages. A comprehensive perspective on linguistic lability across the complete adult life history is not only important for our models of language variation and change, it also counteracts widespread stereotypes about the linguistic abilities of older individuals. </jats:p>