Home > General, The Body, The Face > Symmetry Part 1: Introduction

Symmetry Part 1: Introduction

“Beauty is our weapon against nature; by it we make objects, giving them limit, symmetry, proportion. Beauty halts and freezes the melting flux of nature.”

Camille Paglia 

In the study of attractiveness, symmetry almost always refers to bilateral, mirror, or reflection symmetry: each side is identical to the other when split down the middle – as is the figure on the left. The midsagittal plane – the plane that runs through the body, beginning at the head and passing through the spinal column and the navel, is the marker of mirror symmetry. Bilateral symmetry is common in vertebrates and chordates. It promotes movement, a central nervous system, and cephalization (the development of heads).

While symmetry is expected in development, asymmetry (the absence of symmetry) is common. There are three types of asymmetry: directional asymmetry, antisymmetry, and fluctuating asymmetry (Kowner, 2001).  



Directional Asymmetry (DA): some traits develop more on one side than the other, e.g., the human brain.





  1. Antisymmetry: asymmetric development is typical, but unpredictable, e.g., claw size in fiddler crabs.




  1. Fluctuating Asymmetry (FA): “randomly produced deviations from perfect symmetry of two sides of quantitative traits in an individual for which the population mean of R-L differences is zero and their variability is near-normally distributed” (Kowner, 2001, p.448).  




By-and-large, DA and antisymmetry are understood to contribute to an organism’s fitness. FA, on-the-other-hand, is generally assumed to be an indicator of developmental instability: the inability “of the organism to resist or buffer the disruption of precise development by environmental and genetic stresses” (Kowner, 2001, p. 447). That is, perfect symmetry is the developmental expectation and organisms with genetic weaknesses in particular environments will show this weakness through FA (irregular development).  

Clear connections between facial and body symmetry and attractiveness exist. Connecting the dots:

 Thus, the preference for symmetry is a preference for good genes. This conclusion is straightforward and coherent – but may be premature:

To be clear: I am not opposed to the possibility that there is a connection between FA and DI. I am merely suggesting that beauty researchers emphasize the tentative nature of this connection.

 Wayne Hooke

 Planar image courtesy of Yassine Mrabet

ResearchBlogging.orgKowner, R. (2001). Psychological perspective on human developmental stability and fluctuating asymmetry: Sources, applications and implications British Journal of Psychology, 92 (3), 447-469 DOI: 10.1348/000712601162284

Categories: General, The Body, The Face
  1. Nadia
    August 23, 2009 at 7:17 pm

    For what it’s worth, some are skeptical about the effects of symmetry on attractiveness. Recall Weeden and Sabini’s meta-analysis?

    Consider also:


    Also, both Weeden and Sabini ’05 and Rhodes 2006 were skeptical of good theory. I’m surprised you wouldn’t mention these limitations.

  2. Nadia
    August 23, 2009 at 7:40 pm

    *good genes theory.

    Anyway, I just wanted to say something else. Even though I disagree with some of your critiques of the research, I am very grateful that you run this blog. A lot of attractiveness and body image related research is hyped up and not really scrutinized. The simple reality is that so many journalists offer exaggerated discussions and fail to mention important limitations. I am so glad that you are willing to look beyond glowing press coverage and scrutinize the research. I appreciate it very much!


  3. whooke
    August 24, 2009 at 12:55 pm

    Thanks for the support and the participation! My reading of Weeden and Sabini is that at the time of writing, the exact relationship between symmetry and attractiveness was under review, rather than that symmetry is unrelated to attractiveness. Right out of the gate, directional asymmetry is a big problem with all of the mirror image symmetry studies, which, at least according to Rhodes, is where we find the bulk of the evidence against symmetry being attractive. The Komori study you linked to uses the suspect methodology….


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