Reaction time variability in children is specifically associated with attention problems and regional white matter microstructure

Background: Increased intraindividual variability (IIV) in reaction times (RT) has been suggested as a key cognitive and behavioral marker of attention problems, but findings for other dimensions of psychopathology are less consistent. Moreover, while studies have linked IIV to brain white matter microstructure, large studies testing the robustness of these associations are needed. Methods: We utilized data from the Adolescent Brain Cognitive Development (ABCD) Study baseline assessment to test the associations between IIV and psychopathology (n=8622, age=8.9-11.1), and between IIV and white matter microstructure (n=7958, age=8.9-11.1). IIV was investigated using an ex-Gaussian distribution analysis of RTs in correct response go trials in the stop signal task. Psychopathology was measured by the Child Behavior Checklist and a bifactor structural equation model was performed to extract a general p-factor and specific factors reflecting internalizing, externalizing, and attention problems. To investigate white matter microstructure, fractional anisotropy (FA) and mean (MD), axial (AD), and radial diffusivity (RD) were examined in 23 atlas-based tracts. Results: Increased IIV in both short and long reaction times was positively associated with the specific attention problems factor (Cohen’s d=.13 and d=.15). Increased IIV in long reaction times was also positively associated with RD in the left and right corticospinal tract (d=.12 (both tracts)). Conclusions: Using a large sample and a data-driven dimensional approach to psychopathology, the results provide novel evidence for a small but specific association between IIV and attention problems in children and supports previous findings on the relevance of white matter microstructure for IIV.