Exploring selective attention in ADHD: visual search through space and time

Background: In order to examine the mechanisms mediating selective attention in Attention Deficit Hyperactivity Disorder (ADHD), this study compared the performance of children diagnosed with ADHD to non-clinical controls on a visual search task in three conditions.Method: In the single feature condition, the target differed from distractors in terms of shape only, whilst in the conjunction baseline, the target was defined by shape and colour relative to distractors. In the preview condition, the conjunction stimuli were segmented over time, so that one set of distractors appeared first, followed 1000 ms later by the second set with the target.Results: Although children with ADHD were slower overall than controls, RTs, revealed no difference in search mechanisms between groups; for all children, search was more efficient in the single feature and preview conditions than in the conjunction baseline. However, children with ADHD made more errors, especially in the conjunction and preview conditions.Conclusions: Children with ADHD were not impaired in their mechanisms of visual search relative to controls, but their error patterns implied the adoption of a premature response deadline in the conjunction search condition, and an occasional failure to inhibit old items in the preview condition.