Abstract
When searching for a target object in cluttered environments, our visual system appears to complete missing parts of occluded objects—a mechanism known as “amodal completion.” This study investigated how different variants of completion influence visual search for an occluded target object. In two experiments, participants searched for a target among distractors in displays that either presented composite objects (notched shapes abutting an occluding square) or corresponding simple objects. The results showed enhanced search performance when composite objects were interpreted in terms of a globally completed whole. This search benefit for global completions was found to be dependent on the availability of a coherent, informative simple-object context. Overall, these findings suggest that attentional guidance in visual search may be based on a target “template” that represents a globally completed image of the occluded (target) object in accordance with prior experience.
Highlights
A ubiquitous obstacle that the visual system encounters in object perception is occlusion
For composite objects, only search for the globally completed target afforded faster responses compared to local- and mosaic-type objects
Search for a global interpretation of the composite object was still less efficient than search for a simple global target, which potentially resulted from a perceptual difference between these two types of stimuli (e.g., due to the additional, occluding square in composite objects, see Figure 1(a))
Summary
A ubiquitous obstacle that the visual system encounters in object perception is occlusion. Parts of the objects in our typically complex, cluttered environments may lack a visual stimulus correlate, because they are partly occluded by other structures—which may make it hard to find some searched-for but partially occluded target object. To overcome this limitation and establish continuity, amodal completion has been described as a mechanism that fills in missing perceptual information (Michotte, Thines, & Crabbe , 1964/1991). Global completion emphasizes global relations of the occluded object, in particular symmetry (Buffart, Leeuwenbert, & Restle, 1981) Another alternative might represent an occluded figure in terms of a ‘‘mosaic,’’ that is, without amodal completion
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