Linking temporal dynamics of children’s natural behavior to brain development

Across the school day, children must continually modulate their behavior to be appropriate to the classroom. Yet, children vary in their ability to sustain behavioral regulation over time. We previously showed that daily increases in activity levels (DIA) across the third-grade school day relate to questionnaire measures of self-control, and college completion. Here, we ask how individual differences in brain development relate to children’s ability to sustain behavioral regulation as measured by DIA. We use neuroimaging and actigraphy data from the ABCD study (N = 4,338, Mage = 11.98). We preregistered hypotheses that steeper DIA (lower sustained control) would be associated with thinner cortex, lower surface area, and weaker correlations between the executive control and somatomotor networks. We replicated typical patterns of DIA and associations between steeper DIA and lower inhibitory control. DIA was associated with thinner cortex in areas for executive control (βs = -0.04 to -0.06) and motor action (βs = -0.04 to -0.05). Greater DIA was also associated with lower connectivity between executive control and somatomotor networks (β = -0.07), and greater connectivity within somatomotor network (β = 0.12). DIA is a promising measure of naturalistic self-control for studying between- and within-person variability at scale.