Intraindividual Variability as an Indicator of Cognitive Function: Contrasting Operationalizations and Exploring Mechanisms

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Most research focuses on average performance (how much faster or better does group A perform a task relative to Group B). Unfortunately, this mean-centric focus has overshadowed research on intraindividual variability (IIV) in performance, such as the fluctuations in how fast or slow a given individual responds across a series of response latency trials, or the variation in the cortical haemodynamic response function (i.e., neural complexity) when performing a task. 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 the mean alone. To further our understanding of the characteristic patterns, underlying mechanisms, and correlates of IIV, this research program will: (1) employ and refine novel methodological and advanced quantitative approaches for measuring variability including the use of measurement burst research designs to facilitate indexing short-term (trial-to-trial) fluctuations and long-term (year-to-year) change for IIV in cognitive function, derive and contrast competing operationalizations of cognitive variability, and explore approaches for simultaneous modeling of mean and variability; (2) investigate novel definitions of variability in neural and physiological function (e.g., multiscale entropy for the neural activity signal indexed by NIRS and its superior temporal sampling properties; variability across temporal and spatial gait indicators), and examine these variability indices in relation to cognitive function; and (3) characterize potential mechanisms and processes underlying individual differences in variability by computing associations among cross-domain estimates of variability, by capitalizing on the strengths of the measurement burst design to examine the dynamic time-varying covariation for distinct variability signals and their corresponding impact on cognitive performance (e.g., is neural IIV systematically associated with cognition?), and to explore the malleability of IIV by assessing or manipulating key moderating factors including the impact of dual tasking (increasing cognitive load).******Key advantages of this program include the adoption of an intensive measurement burst design, as well as the use of novel instrumentation already installed in my research laboratory including a GAITRite computerized walkway, as well as a functional near infrared spectroscopy (NIRS) system. The expected significance of this research program to the field of cognitive science lies in the improved understanding of optimal ways to measure and compute estimates of variability, ascertaining whether systematic changes in variability and cognition are associated, and furthering our understanding of the potential mechanisms underlying variability.