Grouping by achromatic color and surface segregation

The study explored the achromatic-color determinants of grouping of uniform surfaces. The stimuli were a set of separate uniform achromatic disks on either a uniform or a bipartite achromatic background. The participants rated the salience of grouping of these disks for different combinations of stimulus luminances. The results show that achromatic color similarity alone could not sufficiently explain the pattern of obtained factorial curves but this factor coupled with the factor of surface segregation could. Luminance contrast similarity per se was found to be unimportant for grouping.