What determines the object-level visual masking: The bottom-up role of topological change.

Object substitution masking (OSM) is said to occur on an object level without a close spatiotemporal proximity of target and mask. An influential account for OSM is "object updating," which espouses that OSM occurs when the target is updated by the mask as they share a single object representation. However, it is unclear what attribute determines whether the mask shares the same object representation as the target. We hypothesize that topological property determines whether a new object representation is built, and hence topological perception modulates object-level masking. We systematically manipulated the similarity between the target and the mask by changing a topological property (number of holes), color, shape, and orientation. We found that the topological change between the target and the mask reduced masking effects of all the other properties. Changing color, shape, or orientation, however, did not affect the masking effect of any other property. The global effect of the topological change remained across a variety of temporal and spatial distances between the target and the mask and was not limited to masking paradigms. Thus, our results suggest that the object representation, constrained by its topological properties, serves as a higher and global level of OSM, influencing the ongoing visual processing of features that are at a lower and local level.