Abstract
Within what reference frames do orientation-related factors of figure-ground organization operate: retinal, environmental/gravitational, or object-based? Previous research showed that the bias toward lower regions is based on retinal directions: Observers whose heads were upside-down perceived the retinally lower (and thus gravitationally upper) region as figural (Vecera, 2004). We extended this line of inquiry to include all known figure-ground cues that have an orientation component: lower-region (Vecera, Vogel, & Woodman, 2002), wider base (Hulleman & Humphreys, 2004), horizontal-vertical orientation (Rubin, 1921), symmetry (Bahnsen, 1928), and familiarity (Peterson, 1994). Observers viewed black/white figure-ground displays with their heads either upright or at an angle for which differences in reference frame should be evident (45, 90, or 180 degrees from upright, depending on the particular factor). Once the observer saw one region as figural, a probe dot was presented, and he/she indicated whether it was on the figural region or not. The results indicate that retinal directions clearly dominate for lower region and wider base, but object-based directions dominate for familiarity and symmetry. The results are discussed as indicating that at least some figure-ground organization cues (e.g., lower region and wider base) operate before orientation constancy. This fact is interesting because the ecological rationale for these figure-ground cues is based on gravitational rather than retinal considerations. Because the world is normally viewed with the head upright, however, retinal directions also support the ecological validity of retinal versions of these factors. (http://socrates.berkeley.edu/∼plab/projects.htm)