Perceptual Representations of Hole-Bearing Surfaces Revealed by Sound-Shape Correspondence

Holes are not independent entities but are perceived only in relation to the surfaces in which they are embedded. While previous studies have primarily focused on the perception of hole shape itself, it remains unclear how the shape of a hole-bearing surface is perceptually represented. The present study examined two competing accounts regarding the representation of hole-bearing surfaces defined by two nested contours: (1) a hole-based representation, in which both the region enclosed by the outer contour (surface) and the region enclosed by the inner contour (hole) are represented as shape-bearing entities, or (2) a surface-based representation, in which the region between the outer and inner contours is represented as a single unified shape. To directly test these accounts, we used a sound–symbolic naming task in which participants chose an appropriate label (bouba or kiki) for hole-bearing surfaces whose outer contour (circle or square) and inner contour (flower-like or star-like) were independently manipulated so that sound–symbolic consistency differed depending on which representational account was assumed. Results showed that naming responses were primarily based on the shape defined by the inner contour. Crucially, reaction times were shortened when the outer and inner contours were sound-symbolically consistent under a hole-based representation. These findings indicate that hole-bearing surfaces are represented in a hole-based manner, such that both the hole interior and the surrounding surface are concurrently represented as shape-bearing entities.