Attentional selection of complex objects: joint effects of surface uniformity and part structure.

What object properties warrant selection by object-based attention? Previous research has suggested that surface uniformity is required for object-based attentional selection (Watson & Kramer, 1999), yet nonuniform objects are encountered frequently. In the present experiments, we investigated the interplay between surface uniformity and part boundaries and their effect on object-based attention. Specifically, we asked if attention can select nonuniform objects whose surface changes occur at part boundaries. Although uniformly colored objects did exhibit object-based effects, we only observed an object-based effect for multicolored objects when surface changes occurred at part boundaries. These findings suggest that attention can only select nonuniform objects when the surface change occurs at a part boundary.