Foveal crowding and segmentation effects in adults with ADHD

This study investigated foveal crowding and segmentation effects in adults with Attention- Deficit/Hyperactivity Disorder (ADHD) compared to neurotypical controls. While visual crowding, the impaired identification of targets surrounded by flanking elements, has been extensively studied in peripheral vision across various populations, its manifestation in central (foveal) vision among adults with ADHD remains insufficiently studied. 45 participants (22 ADHD, 23 controls) completed a computerized visual task involving identification of the direction of a central target letter ("E") under crowded and uncrowded conditions. A subset of 26 participants (14 ADHD, 12 controls) completed an additional segmentation condition in which the target appeared in red while flankers remained black. Accuracy and response times were recorded across varying stimulus durations (30-240 ms). Results indicated that adults with ADHD exhibited significantly stronger foveal crowding Effects and slower response times than controls. Segmentation improved performance in both groups. These findings suggest that perceptual alterations associated with ADHD extend to basic perceptual processes in central vision. The enhanced crowding reflects a reduced ability to filter irrelevant visual information and an increased integration field, which heightens interference between target and flanker signals and thus increases crowding susceptibility. Salient visual cues mitigated these effects by enhancing target distinctiveness. The findings have implications for everyday visual behaviors, including reading and driving in complex environments, where impaired filtering of distracting information may affect performance.