Within-person variability as a dynamic measure of late-life development: New methodologies and future directions

Background: Intra-individual variability is becoming a focus of research in behavioural gerontology due to theoretical and methodological advances. Objective: New directions in the study of intra-individual variability are described and unanswered questions are proposed. Methods: Papers from the special issue of Gerontology on Intra-individual Change are reviewed. Results: Key findings and approaches from this set of papers are identified, including types of latent growth curve models that incorporate dynamic elements and applications to the study of late-life cognition and affect. Theoretical issues that remain unresolved are outlined. Conclusion: Dynamic approaches to the measurement of change provide novel methods to answer new questions and evaluate existing theories. The focus on intra-individual variability adds a valuable dimension to gerontological research that may refine the way we describe behaviour and measure change.