Abstract
The subcortical deficit theory of attention deficit/hyperactivity disorder (ADHD) proposes that persistent lower-order cognitive deficits may underlie ADHD, while the development of higher-order cognitive abilities may be involved in the remission of ADHD related difficulties. The current dissertation investigated extensions of this theory with eighty children aged between 6 and 12 years, half diagnosed with ADHD and half typically developing. In Study I, the patterns of cognitive-related arousal on the long latency trials responsible for the proposed persistent lower-order cognitive deficit of response time variability (RTV) were measured using pupillometry. Results revealed that RTV was associated with arousal lapses, and that age-related reductions in RTV exhibited by older children with ADHD were associated with compensatory arousal recruitment, rather than a reduction in arousal lapses. In Study II, age-related differences in the development of proactive-cognitive control were examined. Results showed that, relative to same aged TD peers, younger children with ADHD were delayed in the development of the higher-order ability of proactive-cognitive control, while older children with ADHD were not. Further, more efficient proactive-cognitive control was related to lower levels of RTV. In Study III, relations between laboratory and ecological measures of performance were examined. It was found that elevated RTV was associated with poorer ecological performance, and that more efficient proactive-cognitive control was related to better ecological performance for children with ADHD. Overall, results from the present dissertation were supportive of the hypothesis that children with ADHD have persistent lower-order cognitive deficits related to performance difficulties, and that the presence of efficient higher-order cognitive functions are associated with the lower overt difficulties related to those persistent deficits. Implications regarding the present literature, and directions for future research are discussed.