The construct validity of daily cognitive variability.

Cognition is a dynamic process and is subject to substantial variation across short and long timescales. It is becoming common to assess cognition repeatedly over short intervals to determine the correlates and consequences of such "cognitive variability." A high-frequency cognitive assessment approach is also an ideal method for measuring how cognition operates in daily life. Nevertheless, several fundamental questions regarding the nature of cognitive variability remain unanswered. We utilize data from the COGITO study, which administered nine separate cognitive tests to more than 200 participants for 100 days to answer the following questions: Do different tasks exhibit similarly reliable levels of variability, and does variability cluster into distinct cognitive domains? This rich data set was analyzed using Bayesian mixed-effects location scale models which simultaneously estimate individual means and variability. All nine tasks exhibited significant variability across the 100 days of testing. Tasks within the domains of episodic memory or processing speed were moderately correlated with each other suggesting some degree of domain specificity. Working memory tasks, on the other hand, did not correlate well with each other suggesting variability in these tasks is dominated by momentary or task-specific influences. These findings not only advance our theoretical understanding of what cognitive variability is but also provide insight into which cognitive tests are most suitable for high-frequency administration and thus may be most amenable to use for studying aging and cognitive processes as they occur in daily life. Appropriate limits on the generalizability of our results are noted. (PsycInfo Database Record (c) 2026 APA, all rights reserved).