Increased sensitivity to perceptual interference in adults with attention deficit hyperactivity disorder.

Difficulty with selective attention is a frequent complaint of adult patients with ADHD, but selective attention tasks have not provided robust evidence of attentional dysfunction in this group. Two experiments examine this puzzle by distinguishing between failures of spatial selection and problems due to sensitivity to perceptual interference. In Experiment 1, we measured the level of perceptual interference generated by targets in crowded displays with nearby distractors by comparing luminance thresholds in both distractor-present (noise) and distractor-absent (clean) displays. ADHD and control participants had comparable thresholds for clean displays, but ADHD individuals had elevated thresholds to crowded displays. These effects could be explained in two distinct ways. Deficits may have arisen from amplified visual interference in the noise condition, or from abnormalities in top-down attentional processes that reduce visual interference. Experiment 2 adjusted for individual perceptual differences with clean and noise displays, before measuring visual interference resolution at attended versus unattended locations. ADHD and control groups had comparable interference resolution at attended locations. These results suggest that perceptual interference rather than spatial attention deficits may account for some deficits in ADHD. This putative deficit in sensory function highlights a potential early-stage perceptual processing deficit in ADHD distinct from selective attention.