Partly occluded visual objects are completed or “filled-in” behind occluding surfaces, allowing the occluded object to appear as a single object that continues behind the occluder.  This filling-in of missing sensory information is known as “amodal completion” (Kanizsa, 1975, 1985; Michotte et al., 1991). Amodal completion is usually known as a modular or cognitive impenetrable process is not affected by observers’ knowledge or experience (Pratt and Sekuler, 2001). Thus previous research focused on the image-based properties that lead to amodal completion.

In the present experiments, we examined the role of a higher-level visual process—visual short-term memory (VSTM)—in amodal completion.  We measured the degree of amodal completion by asking participants to perform an object-based attention task on occluded objects while maintaining either zero or four items in visual working memory. When no items were stored in VSTM, participants completed the occluded objects; when four items were stored in VSTM, amodal completion was halted (Experiment 1).  These results were not caused by the influence of VSTM on object-based attention per se (Experiment 2) or by the specific location of to-be remembered items (Experiment 3).  VSTM interferes with amodal completion, suggesting that amodal completion may not be an ‘infomationally encapsulated’ process but instead can be affected by high-level visual processes.