Effects of symmetry and familiarity on the attractiveness of human faces

The effects of both symmetry (perceptual factor) and familiarity (cognitive factor) on facial attractiveness were investigated. From the photographs of original slightly asymmetric faces, symmetric left-left (LL) and right-right (RR) versions were generated. Familiarity was induced in the learning block using the repetitive presentation of original faces. In the test block participants rated the attractiveness of original, previously seen (familiar) faces, original, not previously seen faces, and both LL and RR versions of all faces. The analysis of variance showed main effects of symmetry. Post hoc tests revealed that asymmetric original faces were rated as more attractive than both LL and RR symmetric versions. Familiarity doesn't have a significant main effect, but the symmetry-familiarity interaction was obtained. Additional post hoc tests indicated that facial attractiveness is positively associated with natural slight asymmetry rather than with perfect symmetry. Also, unfamiliar LL symmetric versions were rated as more attractive than familiar LL versions, whereas familiar RR versions were rated as more attractive than RR unfamiliar faces. These results suggested that symmetry (perceptual factor) and familiarity (cognitive or memorial factor) play differential roles in facial attractiveness, and indicate a relatively stronger effect of the perceptual compared to the cognitive factor.