The ecological validity of delay aversion and response inhibition as measures of impulsivity in AD/HD: A supplement to the NIMH multimodal treatment study of AD/HD

Impulsivity is a primary symptom of the combined type of Attention Deficit/ Hyperactivity Disorder (AD/HD). The Stop Signal Paradigm is premised upon a primary deficit in inhibitory control in AD/HD, whereas the Delay Aversion Hypothesis, by contrast, conceptualizes impulsivity in AD/HD, not as an in ability to inhibit a response, but rather as a choice to avoid delay. This study compared the ecological validity of the Stop Signal Task (SST) and Ch oice-Delay Task (C-DT) measure of delay aversion, with respect to their rel ative utility in discriminating AD/HD children from normal control particip ants, and their correlations with classroom observations and with ratings o f impulsivity and other core AD/HD symptoms on the Conners and SNAP-IV chec klists. The tasks exhibited modest discriminant validity when used individu ally and excellent discriminant validity when used in combination. The C-DT correlated with teacher ratings of impulsivity, hyperactivity, and conduct problems, and with observations of gross motor activity, physical aggressi on, and an AD/HD composite score. The SST correlated with the observations only. These results suggest that delay aversion is associated with a broad range of AD/HD characteristics whereas inhibitory failure seems to tap a mo re discrete dimension of executive control.