Everyday language use overflows with discourse-pragmatic features. Their frequency, form and function can vary greatly across social groups and change dramatically over time. And yet these features have not figured prominently in studies of language variation and change. This book demonstrates the theoretical insights that can be gained into both the structure of synchronic language variation and the interactional mechanisms creating it by subjecting discourse-pragmatic features to systematic variationist analysis. Introducing an innovative methodology that combines principles of variationist linguistics, grammaticalisation studies and conversation analysis, it explores patterns of variation in the formal encoding of I DON’T KNOW, I DON’T THINK and negative polarity tags in a north-east England interview corpus. Speakers strategically exploit the formal variability of these constructions to signal subtle meaning differences and to index social identities closely linked to the variables’ and their variants’ functional compartmentalisation in the variety.