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Vicky Froyen, Jacob Feldman, Manish Singh; Anomalous 3D structure-from-motion arises from accretion-deletion and figure-ground cues. Journal of Vision 2013;13(9):715. doi: https://doi.org/10.1167/13.9.715.
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© ARVO (1962-2015); The Authors (2016-present)
We present a novel phenomenon involving an interaction between accretion-deletion and figure-ground. Our displays consisted of alternating light and dark regions containing random-dot textures, which moved horizontally at constant speed, but in opposite directions in alternating regions. Due to the ambiguous nature of the accretion-deletion cue (accretion-deletion occurs equally on both sides of each contour), they were consistent with a percept of either the light regions being in front, with the dark regions moving amodally behind them; or vice versa. Surprisingly, the regions perceived as figural are also perceived as 3D cylinders rotating in depth---even though each region has constant velocity (hence inconsistent with 3D rotation). However, this allows the visual system to explain accretion-deletion on both sides: On one side accretion-deletion is attributed to occlusion behind another surface, on the other side it is attributed to self-occlusion due to 3D rotation. We found we could easily bias the percept towards either of the two interpretations (light or dark regions as rotating in 3D) by manipulating geometric cues to figure-ground. Our experiments used multiple geometric cues, including convexity, parallelism, symmetry and relative area. Subjects indicated which regions---light or dark---they perceived as rotating. The results showed that geometric cues biased the percept of 3D rotation in proportion to their strength (convexity>parallelism=symmetry). Moreover, the proportion by which subjects perceive a particular region as rotating decreased monotonically with its area size. On the methodological side, this phenomenon provides a novel way of measuring figure-ground perception, since the percept of 3D rotation nicely tracks the strength of the figure-ground cue. On the theoretical side, our results highlight the need for studying geometric figure-ground cues and depth-from-motion cues as an ensemble. The observed interactions between accretion-deletion and geometric figure-ground cues cannot be explained by standard accounts of accretion-deletion or structure-from-motion.
Meeting abstract presented at VSS 2013
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