The proper placement of uniform connectedness.

In this journal, Palmer and Rock (1994) articulated a principle of perceptual organization calleduniform connectedness (UC); and they contended that previous investigators of perception had failed to realize the need for this organizing principle. The authors outlined a theory of perceptual organization that "places the principle of UC at center stage" (p. 38) in that UC was assigned the two privileged roles of (1) forming the fundamental units for later perceptual processes, and (2) yielding the postconstancy regions that correspond to environmental surfaces. In this commentary, I argue that the proposed theory entails a serial ordering of perceptual processes that is inconsistent with current evidence regarding figure-ground organization, stereo fusion, and object recogntion. In addition, I point out that Kurt Koffka (1935) recognized the need for a principle of unit formation similar to the one proposed by Palmer and Rock.