UC San Diego

Previous researchers have proposed that there are two types of symmetry detection: one based on crude preattentive symmetry judgments and another based on detailed scrutiny of individual parts (Barlow Reeves, 1979; S. E. Palmer Hemenway, 1978; Royer, 1981). Four experiments were conducted to examine capacity limits in different symmetry judgments. Observers were required to discriminate between random patterns and approximate symmetry (Experiments 1 and 3) or between perfect and approximate symmetry (Experiments 2 and 4). The patterns were divided into two sets of dots, presented either simultaneously or successively. A comparison of accuracy under these two presentation conditions suggested that symmetry detection involves an analysis that is spatially parallel but coarse, regardless of either task difficulty or task type (detecting symmetry vs. detecting asymmetry).