“…Beyond its biological plausibility, fluid reasoning uniquely mediated (i.e., beyond other neurocognitive constructs) predictions of dimensionally-measured ADHD symptoms from birth weight in two prior studies, although both studies focused on youth with IQs above 70. First, the Arithmetic subtest of the Wechsler Intelligence Scale for Children (WISC; Wechsler, 2003), a measure of fluid reasoning (Keith, Fine, Taub, Reynolds, & Kranzler, 2006; Weiss, Keith, Zhu, & Chen, 2013), mediated birth weight and multi-method/informant ADHD symptoms in a prospective longitudinal study of 222 youth with and without ADHD (ages 5–10 years at baseline, 7–13 years at follow-up; M IQ = 106.88, SD = 14.55, range = 73–144), controlling for demographic factors and co-occurring internalizing and externalizing psychopathology (Morgan, Loo, & Lee, 2016). Indirect effects of other WISC subtests tested alongside Arithmetic (i.e., Digit Span, Vocabulary, Symbol Search) were not significant.…”