Impaired Behavioral Inhibition in Implicit Sequence Learning in Adult ADHD

Abstract

Objective: Deficits in explicit learning and memory have consistently been reported in adult ADHD, but it is less clear whether these deficits reflect deficient attentional processes or specific dysfunctions in memory processes. Studies on implicit learning and memory, which are less dependent on the allocation of attention, have rarely been conducted on adult ADHD. Method: We implemented a modified serial reaction-time task that involves distracting stimuli to investigate implicit sequence learning in 32 adult participants with ADHD and in 32 matched healthy control participants. Results: The participants with ADHD revealed unimpaired implicit learning performance, but they made significantly more errors than the control participants. There was no evidence for impaired error monitoring in the participants with ADHD reflected by a comparable degree of double errors and post-error slowing in the two groups. Conclusion: Reduced efficiency of the inhibition of incorrect responses in implicit sequence learning supports previous findings of impaired behavioral inhibition in adult ADHD.