This book is the first to explore the development of sociolinguistic competence among adult second language (L2) learners in Austria, considering both productive and interpretive skills. Combining results from a cross-sectional and longitudinal micro-development study, this book focuses on issues of inter- and intra-individual variation and explores (a) why L2 learners acquire sociolinguistic competence, (b) which aspects of it they acquire, (c) which factors influence it and (d) when they acquire it, as well as how individuals measure up to group averages and the temporal dynamics involved in the development of sociolinguistic competence. The work is notable for its interdisciplinary nature, connecting topics rarely found in the same empirical piece, such as the roles of cognitive and psycholinguistic factors, the intra-individual longitudinal design, and the analysis of group and individual data. In addition, it offers new and valuable insights into issues of language acquisition, including group-to-individual generalisability, the benefits of mixed-methods approaches and the complex, late-acquired nature of many of the components of sociolinguistic competence.