Piecemeal organization and cognitive components in object perception: Perceptually coupled responses to moving objects

Abstract

In three xperiments, observers who were instructed to perceive one of two alternative d pth arrange-ments of a three-dimensional wire cube fixated near one of two intersections that differed in the degree to which they specified the cube's veridical depth organization. I order to separate perceptual effects from experimenter effects, we measured indirect reports about variables perceptually coupled to perceived depth rather than direct reports about perceived depth. In all three xperiments, reversal durations at the two intersections differed, even though the two were parts of a single object. In addition, reversals varied with viewers ' intentions. Thus, the unit of perceptual organization may be smaller than the entire object, and viewers ' intentions can influence the perception of real moving objects. In additional analyses, reversal durations were separated into two components: nonelective instability and malleability; the question of whether these two components of ambiguity are func-tionally distinct could not be decided. Some objects and events are patently ambiguous in that they change in appearance from time to time, even though the stimu-lus objects themselves remain unchanged. For example, the re-versible Necker cube shown in Figure 1A can be seen in either one of the two organizations shown in Figures IB and IC. Al-though ambiguity isoften said to be confined to static line draw-ings and other artificially impoverished stimuli (e.g., Gibson