Dynamic Grouping Motion and Amodal Completion

Objects in a scene are likely to occlude other objects partially and are itself likely
to be partially occluded. A central question, therefore, is how the visual system resolves
the resulting surface correspondence problem by successfully determining which surfaces
belong to which objects. To this end, a recently developed dynamic grouping
methodology has determined whether pairs of adjacent surfaces are grouped (Hock &
Nichols, 2012). The grouping of adjacent surfaces, which depends on their affinity state,
is indicated by the direction of perceived motion across one surface when its luminance is
perturbed. In the current stimuli, which consists of a horizontal surface partially occluded
by a vertical bar, dynamic grouping also can occur for nonadjacent surfaces, providing
they are linked in two-dimensions by a connecting surface. Results indicate that the
dynamic grouping motion is stronger for amodal completion entailing the perceptual
grouping of nonadjacent surfaces behind an occluder.