Abstract
The perception of a target usually deteriorates when flanked by neighboring elements, so-called crowding. Explanations of crowding in the periphery and the fovea are often based on local neural interactions, such as spatial pooling, excessive feature integration, or lateral inhibition. In contrast, we proposed that the grouping of the target with the flankers determines crowding. In a visual search task, a target that differed from distractors by its unique color (pop-out) yielded faster reaction times than a target that differed by a combination of color and size (no pop-out; serial search). Identical stimulus configurations, but now presented for only 150 msec, included a vernier target that required the observer's judgment of the direction of the offset. Even though the location of the target within the array was marked in both, the proportion of correct vernier responses was far higher (83.2%) for the pop-out configurations than for the ones requiring serial search (59.6%, p<0.05). The results are interpreted as further evidence that perceptual grouping of the target with the flankers plays an important role in crowding.