Crowding and perceptual organization: Target's objecthood influences the relative strength of part-level and configural-level crowding.

In visual crowding, identification of a peripheral object is impaired by nearby objects. Recent studies have demonstrated that crowding is not limited only to interaction between low-level features or parts, as presumed by most models of crowding, but can also occur between high-level, configural representations of objects. In this study we show that the relative strength of crowding at the part level versus the configural level is dependent on the strength of the target's perceptual organization. The target's strength of organization was manipulated by presence or absence of closure and good continuation or by proximity between the target's parts. The flankers were similar either to the target parts or to the target configuration. The stronger the target's organization was, the weaker the crowding was by part flankers (Experiments 1 and 2). Most importantly, the target's strength of organization interacted with target-flanker similarity, such that crowding by target-flanker similarity in configuration was greater than that by target-flanker similarity in parts for strongly organized targets, but lesser for weakly organized targets (Experiments 3 and 4). These results provide strong evidence that perceptual-organization processes play an important role in crowding.