The Impact of Symmetry on the Efficiency of Human Face Perception

The presence of symmetric properties in a stimulus has been shown to often exert an influence on perception and information processing. Investigations into symmetry have given rise to the notion that it is processed easily and efficiently by the human visual system. However, only a handful of studies have attempted to actually measure symmetry's role in the efficiency of information use. We explored the impact of symmetry on the perception of human faces, a domain where it has been thought to play a particularly important role. Specifically, we measured information processing efficiency, defined as human performance relative to that of an ideal observer, for the detection, discrimination, and identification of symmetric and asymmetric faces. Surprisingly, we found no evidence for significant differences in efficiency between these two classes of stimuli. Training yielded significant improvements in overall efficiency, but had no significant effect on the relative efficiency of asymmetric and symmetric face identification. Our results indicate that although symmetry may be important to other aspects of face perception (e.g., perceived beauty), it has no discernible impact upon the efficiency with which information is used when detecting, discriminating, and identifying faces.