Perception of a surface split induced by globally inconsistent kinetic occlusion: Objects with salient parts break apart easily

Unlike previous studies of part-based shape representations that mostly investigated static images, we tested whether part segmentation can affect the perception of ambiguous dynamic events, involving globally inconsistent kinetic occlusion: An object moved horizontally across another stationary object, with either its top or bottom half occluding and the other half being occluded by the stationary one, which could be perceived as one object being split into halves by the other object. We manipulated an object's part structure by introducing concave or convex cusps along the contour of an object and found that objects with concave cusps were more likely perceived as being split than those with no or convex cusps. This study provides a new insight into a broad framework of spatiotemporal perceptual organization, by demonstrating that salient parts are readily perceived as broken apart in a physical sense, which in turn alters the perception of a motion event and its causal structure.