An explorative study of peculiar cue of relative distance in perceptual folding.

ABSTRACT: This work is a widening of findings concerning a peculiar case of amodal completion, the completion by folding. It occurs when four quadrilaterals look like a rectangular sheet of paper folded around an interposed rectangle, even when there are not the conditions for a geometric folding (Massironi & Bressanelli, 2002). In this work a simple geometric measure, the lateral separation between the left and right visible parts of the strip, was considered as a possible cue to distance, that is, the measure might be a cue to separation in depth between the two parts of the strip. Two experiments were conducted in order to verify the presence of perceived depth separation between the two parts of the strip and the role of the different lateral separations on the depth perception. In experiment 1 we used an indirect measure of depth: the size constancy effect. In experiment 2 we directly rated the apparent separation in depth between the two parts of the folded strip. Results lent support to the experimental hypothesis.