Symmetry and Visual Appeal

Abstract

S ymmetry and V isual A ppeal Shirley Shao Figure 1: In Rhodes 1995 study, people were asked to rate how attractive these faces (each manipulated to display varying levels of symmetry) were. The most symmetrical One logical proposal for the attractiveness of facial symmetry lies in the idea of “perceptual bias.” By this principle, people are predisposed to recognize certain stimuli in a certain way, preventing information from being processed in a wholly objective way (Gross, 2015). Human vision is built on bilateral symmetry – we have two eyes, one on each side of our face; the muscles associated with each eye’s vision likewise display bilateral symmetry. Human vision can also be naturally divided into two fields – left, and right. When a visual point on one field can be matched to one on the other half of their field, the brain is able to process the visual information, and create a mental image with much more ease. Literally, a person with a symmetrical face is “easy on the eyes.” Similarly, symmetry provides a template that allows a person’s brain to construct at least half of an internal prototype that new information can be matched to. This rough outline that symmetry creates would also explain why people who have “average” looking faces are generally more attractive (Little, 2003). By this vein of logic, faces that are symmetrical, but presented as upside down (with the mouth above the eyes, for example) should also be thought of as more attractive. However, this is not true – once the face we are viewing is inverted and therefore no longer upright, symmetry no longer increases the attractiveness of said face. An alternate explanation looks at the supposed genetic benefits conferred on a person with excellent facial symmetry. A mate can offer two different types of benefits – direct, and indirect. “Financial security” is an example of the former case, and does not necessarily measure a mate’s genetic mettle. Rather, direct benefits confer a person and their offspring with an advantage in the present day; for example, an abundance of wealth or social status is immediately useful to a person and his or her offspring. Indirect benefits are subtler, and could entail long-term genetic benefits for future offspring. These then calls into question what, if any genetic benefits that facial symmetry could imply (Little, 2011). Of note is that there are two different types of facial symmetry to consider. One is “fluctuating asymmetry” (hereon abbreviated as FA), and “directional asymmetry” (known as DA). Directional asymmetry is asymmetry that takes into account the prevalence of hemi-face dominance; in these situations, the line of symmetry splitting the face of a person who exhibits directional asymmetry will not be in the center middle of his or face. Rather, human faces are often larger on the right side, and this asymmetry is exploited when one is trying to convey different states of mind. For example, people are wont to show more of the right side of their face when they want to hide their emotions (Simmons, 2004). B erkeley S cientific J ournal • S ymmetry • F all 2015 • V olume 20 • I ssue 1 • 7 B S J We are so used to the perfectly drawn faces in fairytale books or magazines, that when asymmetry appears in real life, we are startled. We notice people with lopsided smiles, or grins that are adorned with one dimple instead of two; we use eyeliner and layers of eyeshadow to cover up a size difference between two eyes. A face with a mole on one cheek but not on the other makes us pause, and we marvel over the perfect geometry of a beautiful movie star’s symmetrical face. Our eyes are highly equipped to detect bilateral facial symmetry, implying that facial symmetry must be important in some way. Symmetry in other objects can be detected by low-level visual mechanisms, but the detection of symmetry in one’s face calls upon higher-level, more complicated visual mechanisms. Was there an evolutionary pressure to develop these higher-level visual mechanisms, so that we would better be able to detect facial symmetry? (Rhodes, 2005). Correlation does not necessarily indicate causation, but the signs of a strong positive correlation between symmetry and visual appeal seem apparent. In one study, photo manipulation was used to generate faces with varying levels of facial symmetry. The people who were asked to judge this series of faces consistently selected the faces with the greatest bilateral symmetry as most attractive (Rhodes, 1995). As given by Little’s 2011 paper on facial attractiveness, symmetry can be defined as “the extent to which one-half of an object is the same as the other half (Little, 2011).” What, if anything, does symmetry have to do with facial attractiveness?