What Is Intra-individual Variation in Language?

Empirical and experimental work has yielded burgeoning evidence of intra-individual variation drawing on a variety of analytical frameworks and methodological approaches. A systematic review of intra-individual variation is thus timely both to provide guidance for researchers wishing to interpret and understand intra-individual variation and to provide some theoretical and methodological resources to evaluate the rapidly growing body of literature on intra-individual variation. The present chapter thus untangles intra-individual variation both terminologically and conceptually. We survey the scholarly discussion and evaluation of intra-individual variation in the interdisciplinary discourse of theoretical linguistic frameworks and empirical studies. By sketching previous research, we systematise various types of intra-individual and derive the proposal for a model of intra-individual variation followed by some remarks about the application of intra-individual variation.