A simple proximity heuristic allows tracking of multiple objects through occlusion

Moving objects in the world present a challenge to the visual system, in that they often move in and out of view as they are occluded by other surfaces. Nevertheless, the ability to track multiple objects through periods of occlusion is surprisingly robust. Here, we identify a simple heuristic that underlies this ability: Pre- and postocclusion views of objects are linked together solely by their spatial proximity. Tracking through occlusion was always improved when the postocclusion instances reappeared closer to the preocclusion views. Strikingly, this was true even when objects' previous trajectories predicted different reappearance locations and when objects reappeared "too close," from invisible "slits" in empty space, rather than from more distant occluder contours. Tracking through occlusion appears to rely only on spatial proximity, and not on encoding heading information, likely reappearance locations, or the visible structure of occluders.