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Elan B. Barenholtz, Jacob Feldman; The determination of visual figure and ground in dynamically transforming shapes. Journal of Vision 2005;5(8):973. doi: 10.1167/5.8.973.
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© ARVO (1962-2015); The Authors (2016-present)
Figure/ground assignment is a critical step in early visual analysis, upon which much later processing depends. Previously identified cues to figural assignment exclusively involve static geometric factors—such as convexity, symmetry, and size—in non-moving images. Here, we introduce a new class of cue to figural assignment based on the motion of dynamically deforming contours. Subjects viewing an animated, deforming shape tended to assign figure and ground so that articulating curvature extrema—i.e. “hinging” vertices— had negative curvature. This bias is present when all known static geometrical cues to figure/ground are absent or neutral in each of the individual frames of the animation and instead depends on a preference with regard to dynamic contour motion. In addition, this bias for certain deformation properties even seems to override a number of well-known static cues, including smaller area and convexity, when they are in opposition to the motion cue in the same display. We propose that the phenomenon reflects the visual system's inbuilt expectations about the way shapes will deform—specifically, via the articulation of rigid parts at concave part boundaries. This preference is consistent with the underlying structure of biological organisms consisting of rigid limbs, formed over skeletal segments, connected at axial joints. These results point to a novel role for shape partitioning at negative minima and, more generally, suggest a prominent, and largely overlooked, role of dynamic factors in shape and object perception.
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