Facial symmetry

Facial symmetry is one specific measure of bodily symmetry. Along with traits such as averageness and youthfulness it influences judgments of aesthetic traits of physical attractiveness and beauty. For instance, in mate selection, people have been shown to have a preference for symmetry. Facial bilateral symmetry is typically defined as fluctuating asymmetry of the face comparing random differences in facial features of the two sides of the face. The human face also has systematic, directional asymmetry: on average, the face (mouth, nose and eyes) sits systematically to the left with respect to the axis through the ears, the so-called aurofacial asymmetry. Directional asymmetry is a systematic asymmetry of some parts of the face across the population. A theory of directional asymmetries in the human body is the axial twist hypothesis. As predicted by this theory, the eyes, nose and mouth are, on average, located slightly to the left of the axis through the ears. This aurofacial asymmetry is very small in young adults (0.5 degree), but much larger in small children (4 degrees). Fluctuating asymmetry Fluctuating asymmetry is the non-systematic variation of individual facial landmarks with respect to the facial midline, i.e., the line perpendicular to the line through the eyes, which crosses the tip of the nose and the chin. A wide variety of methods have been used to examine the claim that facial symmetry plays a role in judgments of beauty. Blending of multiple faces to create a composite and face-half mirroring have been among the techniques used. Alex Dodge 2012 left.jpg|2 right sides Alex Dodge 2012.jpg|Original Alex Dodge 2012 right.jpg|2 left sides Conclusions derived from face mirroring, however, have been called into question, because it has been shown that mirroring face-halves creates artificial features. For example, if the nose of an individual is slightly bent to the right side, then mirroring the right side of the face will lead to an over-sized nose, while mirroring the left side will lead to an unnaturally small nose.