Performance on a neurocognitive measure of alerting differentiates ADHD combined and inattentive subtypes: a preliminary report.

The performance of 16 attention-deficit hyperactivity disorder (ADHD)/C, 26 ADHD/IA, and 24 control children was compared using a computer reaction time task designed to measure the effects of Posner's orienting, conflict and alerting attentional systems. No group differences in orienting or conflict were found. In contrast, children with ADHD/IA showed stronger alerting effects than those with ADHD/C, as indicated by relatively greater performance benefits following a warning cue. Although neither ADHD group differed significantly from controls on alerting, effect size comparisons indicated that children with ADHD/IA showed a somewhat larger (d=.57) and children with ADHD/C a somewhat smaller (d=.44) alerting effect relative to control children. The results are among the first to document unique patterns of attentional capacity for ADHD subtypes.