Complete mergeability and amodal completion

When image fragments are taken to correspond to the visible portions of a s ingle occluded object, the object is said to 'amodally complete' behind the occluder. Kellman and Shipley (Kellman, P. J., & Shipley, T. F. (1991). A theory of visual interpolation in objective perception. Cognitive Psycholog y, 23, 144-221) argued that when the virtual contour extensions of such ima ge fragments subtend an obtuse or right angle, the contours are 'relatable' and therefore complete. However, edge and surface relatability are neither necessary nor sufficient for completion to be perceived (Tse, P. U. (1999) Volume completion. Cognitive Psychology). Evidence is offered that complet ion is not driven directly by image cues such as contour relatability, but is driven, rather, by intermediate representations, such as volumes that ar e inferred from global image cue relationships. Evidence suggests that seve ral factors, none of which is necessary for amodal completion to occur, con tribute to the perceived strength of amodal completion, including similarit y of pattern or substance, proximity, and good volume continuation or compl ete mergeability. Two partially occluded volumes are completely mergeable w hen they can be extended into occluded space along the trajectory defined b y their visible surfaces such that they merge entirely with each other. Mer geability is not measurable in the image because it describes an inferred r elationship among volumes that must themselves be inferred from the image. (C) 1999 Elsevier Science B.V. All rights reserved. PsycINFO classification : 2323.