3-D constraints on spatially parallel shape perception.

We report evidence from three sets of experiments dealing with spatially parallel grouping of parts in single objects. A first set of experiments demonstrates that parts can be encoded in a spatially parallel manner in three-dimensional (3-D) objects, while there is a serial selection of parts across objects. A second set of experiments further shows that grouping in 3-D is less affected by eliminating collinearity between the parts of objects than grouping in two dimensions, suggesting that 3-D constraints operate directly on visual grouping. A final pair of experiments demonstrates that rotating the elements in the plane, to make a physically unstable 3-D object, disrupts the benefit found with 3-D stimuli when collinearity is eliminated. The evidence indicates that there is rapid and spatially parallel encoding of 3-D object descriptions in vision.