Bouba and Kiki inside objects: Sound-shape correspondence for objects with a hole

Visual holes (cutouts in a surface) have recently intrigued vision scientists as interesting and useful stimuli in the studies of shape perception and as a perceptual conundrum regarding figure/ground organization. Adopting the Bouba/Kiki paradigm, this study addressed a controversial issue of whether the perceived shape of a closed region alters when the region changes from a solid object to an empty hole, in a more direct manner than previous studies did. Observers were presented with two doughnut-like cardboard cutouts, one with a flower-shaped hole and the other with a star-shaped hole, and then matched them with two nonsense words. The curvature profile of the hole boundary was manipulated so that the shape of the interior region (i.e., a hole) and that of the exterior region (i.e., material edges) give rise to opposite shape impressions (i.e., one rounded and the other spiky). The results of Experiment 1 revealed that shape-name matching for holed objects is based on the interior shapes of holes, but not those of materially defined inner edges. The following three experiments replicated the same pattern of results even when holes appeared like oral apertures in animal character faces (Experiments 2-3) and when they were irregular, non-symmetric, and low in semantic association with familiar real-world objects (Experiment 4). Lastly, Experiment 5 showed that shape-name matching for "C"-shaped, negative-part stimuli is also interior-shape-based if the opening of the interior region is relatively small. These findings suggest that the interior shapes of holes are automatically accessible. I conclude with a discussion of my hypothesis that the only global-level, unitary shape representation of a bounded region of a single connected surface is that of the interior region for both objects and holes, imposing an important constraint in visual shape processing.