A Multidisciplinary View on Intraindividual Variability: Capturing the Ups and Downs of Human Behaviour

People are remarkably inconsistent. From behavior to neurotransmitter activity, variability is the rule, not the exception. However, data- and analytic challenges have hindered empirical progress. Here, we highlight technological and methodological innovations that provide new insights into human variability and its relations to learning, cognitive performance, brain function, and aging.