The interaction of luminance, velocity, and shape information in the perception of motion transparency, coherence,...

The perception of luminance transparency for superimposed patterns depends on how luminance, figural, and topological conditions are simultaneously satisfied. Motion transparency or coherence for two superimposed patterns, which correspond to the perception of both patterns moving across one another or to the perception of compound motion of the regions of pattern intersection, depends on the relation between the local velocity, luminance, and shape information. This study analyzes how luminance, shape, and local velocity interact in the perception of motion transparency and coherence. Psychophysical experiments done with sinusoidally modulated bar patterns are presented which show that the perception of motion transparency or coherence can be described as the result of the interaction of two integration modules: the velocity-luminance and the velocity-shape processes. The velocity-luminance process describes the integration of the local velocity with luminance information. When the luminance transparency rules are satisfied this process always generates the perception of motion transparency independently of the shape or contour information. On the other hand, when the luminance transparency rules are violated one can either perceive motion coherence or non-rigid motion; one perceives motion coherence when the patterns have small or zero amplitude, and non-rigid motion when the patterns have large amplitude. The velocity-shape process describes the integration of local velocity with shape information, and this depends on the relation between the error in the extraction of the local velocity and the magnitude of the contour amplitude. As a result of these experiments it is conjectured that the velocity-luminance and the velocity-shape processes do interact constructively or destructively. The constructive interaction occurs when the luminance transparency rules are satisfied. The destructive interaction occurs when the luminance transparency rules are violated, and such that, although the patterns contain sufficient shape information to solve the aperture problem and therefore generate the perception of motion transparency, one perceives non-rigid motion. This shows that global information describing the stratification of superimposed patterns can affect the integration of local velocity information with, for example, shape information, and this is not described by current motion theories.