Attending to the parts of a single object: Part-based selection limitations

Studies of object-based attention have demonstrated poorer performance in d ividing attention between two objects in a scene than in focusing attention on a single object. However objects often are composed of several parts, a nd parts are central to theories of object recognition. Are parts also impo rtant for visual attention? That is, can attention be limited in the number of parts processed simultaneously? We addressed this question in four expe riments. In Experiments 1 and 2, participants reported two attributes that appeared on the same part or on different parts of a single multipart objec t. Participants were more accurate in reporting the attributes on the same part than attributes on different parts. This part-based effect was not inf luenced by the spatial distance between the parts, ruling out a simple spat ial attention interpretation of our results. A control study demonstrated t hat our spatial manipulation was sufficient to observe shifts of spatial at tention. This study revealed an effect of spatial distance, indicating that our spatial manipulation was adequate for observing spatial attention. The absence of a distance effect in Experiments 1 and 2 suggests that part-bas ed attention may not rely entirely on simple shifts of spatial attention. F inally, in Experiment 4 we found evidence for part-based attention, using s timuli controlled for the distance between the parts of an object. The resu lts of these experiments indicate that visual attention can selectively pro cess the parts of an object. We discuss the relationship between parts and objects and the locus of part-based attentional selection.