My research focuses mainly on cognitive function in later life from a lifespan individual differences perspective – on normal patterns as well as on the impact of disease and other characteristics and risk factors. I am particularly interested in the universal challenges of science: on developing construct measurements, study designs and statistical analyses to address essential developmental questions. My attention is currently on issues surrounding the specification of time in longitudinal models. These interests come together in my work with the Integrative Analysis of Longitudinal Studies on Aging (IALSA) network. This collaborative international network provides extensive opportunities for coordinated analysis and replication of developmental research from a within-person perspective.