Abstract
While contours bounding holes (cutouts in a surface) are perceptually assigned to the surrounding surface, people can perceive the shapes of holes as well as figural objects. Reflecting this paradox, recently there has been an ongoing debate on holes’ figural status. Previous studies on attention have indicated that the object-based attentional effect diminishes when an object is replaced by a hole, suggesting that holes are perceptually organized as the background. To further investigate whether the representation of a hole corresponds to the background region seen through the hole or its immaterial surface enclosed by a material object, we utilized “object-based warping” (Vickery & Chun, 2010)—an illusion where two dots within an object appear farther apart than two equidistant dots in empty space. Participants viewed 3D stereoscopic displays where reference dots, surrounded by a rectangular region—a solid object (Experiment 1) or an empty hole (Experiment 2)—were shown along with adjustment dots. They manipulated adjustment dot spacing to match that of the reference dots. We compared judgments when the dots were placed in different depth planes (i.e., on, in front of, or behind the rectangle). In Experiment 1, the warping effect was more pronounced when the dots were on the object’s surface than when they were in front of it. In Experiment 2, where a rectangular hole surrounded reference dots, the warping effect was greater when reference dots were at the same depth plane as the hole (i.e., on the immaterial surface) compared to when they were both in front of the hole and on the background visible through it. These findings suggest (1) that the warping effect is surface-based and (2) that in terms of object-based attention, the representation of a hole corresponds to the immaterial surface enclosed by the contour rather than the background seen through it.