Characteristics and Correlates of Intraindividual Variability in Executive Control Processes

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Most scientific research focuses on average performance (how much faster does group A perform a task relative to Group B). Unfortunately, this focus on mean performance has largely overshadowed research on variability in performance, such as the fluctuations in how fast or slow a given individual responds across a series of trials. Growing consensus from various scientific disciplines, including cognitive neuroscience, neuropsychology, and mathematical modeling, suggests that theoretically interesting aspects of cognitive function are not captured by mean group performance. Moreover, strong claims are made that reliance on mean performance estimates may reflect a critical oversimplification of behavior patterns. Measures of executive function, reflecting our ability to attend to important information or inhibit irrelevant detail, are particularly well suited for assessing variability. Recent findings have shown that performance fluctuations across response latency trials are pronounced for executive measures, increase under more difficult task conditions, and are associated with brain structures linked to efficient executive processes. Despite growing interest in variability across disciplines, key questions endure. To further our understanding of the nature, underlying mechanisms, and correlates of performance variability, this research program will examine three key research objectives including: (1) the direct comparison of competing definitions of variability for measures of cognitive (executive function), physiological (gait), and brain (blood oxygen level dependent or BOLD response) function; (2) the examination of associations among changes in the various indices of variability (are fluctuations in cognitive functioning linked to fluctuations in brain activation patterns?), as well as change in other indicators (stress, brain structure and function), across short-term (trial-to-trial) and long-term (year-to-year) follow-up intervals; and (3) the identification of potential processes underlying increased variability by assessing or manipulating key factors such as cognitive training and cognitive load.