Abstract
Attention deficit hyperactivity disorder (ADHD) is a commonly diagnosed neurodevelopmental disorder. Crowding is a perceptual phenomenon in which a target, which is easily recognized on its own, becomes difficult to recognize in clutter. The “pop-out” effect occurs, when the target has unique features, among a set of homogeneous distracting items surrounding it and is discussed in terms of attention (preattentive or attentive). Recent findings show that pop-out abolishes the crowding effect. Thus, we explored how crowding affects processing in adults with ADHD and if their performance improves from the pop-out effect. Prior to experimental testing we ran a computerized diagnostic test (Mindstream) on 25 adults, ages 18-40, in order to divide participants into separate groups (ADHD/controls). All participants had normal or corrected to normal vision. In the crowding task participants were asked to determine the direction of the target E in (black/red) embedded in a matrix of random black Es. The red E served as a pop-out condition. The tests were performed in foveal vision conditions at different presentation times (30,60,120,240ms). In the ADHD group the crowding effect (crowded/uncrowded conditions) was significantly higher than the control group (p = 0.04) and the reaction time (both uncrowded and crowded conditions) was significantly longer (slower) (p = 0.02). The pop-out tasks reduced the crowding effect in both groups but was more effective in ADHD (recognition of E). However, reaction time remains longer among ADHD participants. We suggest that by tagging the target in red created a pop-out effect and uncrowded the target improving the ADHD participants’ performance. However, performance of the ADHD group remains less accurate than controls, especially at short presentation times. The results also indicate that the visual processing in ADHD is significantly slower and inferior to the controls, suggesting new insights into the relationships between ADHD and visual functions.