Rethinking hyperactivity in pediatric ADHD: Preliminary evidence for a reconceptualization of hyperactivity/impulsivity from the perspective of informant perceptual processes

Hyperactivity is a core ADHD symptom that has been both positively and negatively associated with cognition and functional outcomes. The reason for these conflicting findings is unclear but may relate to subjective assessments that conflate excess physical movement (hyperactivity) with verbally intrusive/ impulsive behaviors. The current study adopted a model-driven, rational-empirical approach to distinguish excess physical movement symptoms from other, auditorily perceived behaviors assessed under the "hyperactivity/impulsivity" umbrella. We then tested this alternative conceptualization's fit, reliability, replicability, convergent/divergent validity via actigraphy, and generalizability across informants (parents, teachers) in a well-characterized, clinically evaluated sample of 132 children ages 8-13 years (M 10.34, SD = 1.51; 47 girls; 67% White/non-Hispanic). The current DSM hyperactivity/impulsivity item pool can be reliably reclassified by knowledgeable judges into items reflecting excess physical movement (visual hyperactivity) and auditory interruptions (verbal intrusion). This bifactor structure showed evidence for multidimensionality and superior model fit relative to traditional hyperactivity/impulsivity models. The resultant visual hyperactivity factor was reliable, replicable, and showed strong convergent validity evidence via associations with objectively assessed hyperactivity. The verbal intrusion factor also showed evidence for reliability and explained a substantive portion of reliable variance, but demonstrated lower estimated replicability. These findings provide preliminary support for conceptualizing ADHD symptoms from the perspective of their cognitive-perceptual impact on others, as well as differentiating excess physical movement (hyperactivity) from other behaviors assessed under the hyperactivity/ impulsivity umbrella. "Verbal intrusion" appears to provide a better explanation than "impulsivity" for the reliable, non-hyperactivity variance assessed by these items, but the current item set appears insufficient for replicable measurement of this construct.