| dc.description | The view that Attention Deficit Hyperactivity Disorder (ADHD) is a disorder of inhibitory control has recently gathered considerable support. Barkley (1997a) proposed a model of ADHD in which response inhibition is the primary deficit that sets the stage for all of the observed deficits in executive functioning and behaviour. Inhibition is a diverse construct, however, and it is unlikely that children who have deficits in one type of inhibition would necessarily have deficits on all types of inhibition. To assess the scope of the inhibitory control deficit in ADHD, children with (n = 16) and without (n = 24) ADHD were tested on seven different measures of inhibition. Participants ranged in age from 9 to 13 years, and the control and ADHD groups were matched for age and sex. The results were interpreted in the context of a recent taxonomy of inhibition proposed by Nigg (2001). Children with ADHD had longer Stop Signal Reaction Times than control children, and they made more exogenously triggered premature saccades on the Memory-Guided Saccade task. Each of these patterns reflects a deficit in the ability to inhibit prepotent responses or to stop ongoing responses; both are subsumed under Nigg's Executive Motor Inhibition. Children with ADHD showed more interference on the Stroop Colour Word Task, but not on the Simon and Flanker tasks. Kornblum's (1994) dimensional overlap model provides a framework for understanding the pattern across these three measures of Executive Interference Control. There were no group differences on the two measures of Automatic Inhibition: Negative Priming and Inhibition of Return. Taken together, these data limit the scope of the inhibitory control deficit in ADHD to response inhibition. The pattern of findings provides support for Nigg's taxonomy of inhibition, for Kornblum's dimensional overlap model of interference, and for Barkley's model of ADHD. | en_US |
