While physical connection strongly supports perceptual integration of visual elements or parts into single objects, concavities along an object's contour strongly induce segmentation of objects into different parts. By means of a matching task, we examine whether the seg mentation of connected parts and the grouping of disconnected parts imply differences in representational unity. All match trials consisted of either two identical configurations or two 180 degrees rotated versions of an otherwise identical configuration, whereas mismatch trials had one misoriented part, Results show that the 180 degrees matches with the physically disconnected parts were relatively slower than similar matches with physically connected parts,although the connections could be minimal (deep concavities, corner to edge connection). This suggests that the mental operation required for the 180 degrees match has more difficulty with the disconnected parts, indicating a measurably lower degree of representational unity. (C) 1998 Elsevier Science B.V. All rights reserved.