3-D constraints on spatially parallel shape perception

We report evidence from three sets of experiments dealing with spatially pa rallel grouping of parts in single objects. A first set of experiments demo nstrates that parts can be encoded in a spatially parallel manner in three- dimensional (3-D) objects, while there is a serial selection of parts acros s objects. A second set of experiments further shows that grouping in 3-D i s less affected by eliminating collinearity between the parts of objects th an grouping in two dimensions, suggesting that 3-D constraints operate dire ctly on visual grouping. A final pair of experiments demonstrates that rota ting the elements in the plane, to make a physically unstable 3-D object, d isrupts 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.