A continuous-time approach to short-term activity-cognition dynamics

Prior research suggests that naturally occurring leisure activities may exert short-term, time-lagged benefits on cognition over hours in middle- and older aged adults. We extended this work by examining short-term activity-cognition dynamics in two ambulatory assessment studies of U.S. adults spanning diverse demographic backgrounds, using a continuous-time modeling framework. Both studies involved repeated smartphone-based assessments of leisure activities (cognitive [Study 1 only], social, physical, and passive) and cognitive performance (processing speed and spatial working memory) over 2 weeks. Study 1 included 288 older adults (n_observations = 16,057, M_age = 77.08, 58% non-White). Hierarchical Bayesian continuous-time dynamic models indicated that, compared with intervals without cognitive, social, or passive activities, intervals with these activities showed beneficial within-person cross-effects on subsequent processing speed and working memory over hours. In contrast, activities and cognition showed negative within-person correlated random fluctuations, reflecting faster timescale co-occurring relations in opposite directions. At the between-person level, more frequent engagement in cognitive, social, and physical activities was associated with better cognition, whereas greater engagement in passive activities was associated with poorer cognition. Study 2 included 224 young and middle-aged adults (n_observations = 12,928, M_age = 44.67, 92% non-White). Replicating the older adult findings, moments dominated by passive activities showed beneficial within-person cross-effects on subsequent processing speed, alongside negatively correlated random fluctuations. In contrast, between-person associations indicated that greater engagement in passive activities was related to better working memory. Overall, these findings demonstrate short-term activity-cognition cross-effects while underscoring their complexity, as associations may differ across timescales and life stages. (PsycInfo Database Record (c) 2026 APA, all rights reserved).