Beauty lies in the eye of the beholder, says the poet, but according to the heartless scientist, that’s just a load of flowery hogwash. Ever since Richard Dawkins accused our genes of being selfish, the big and scary man in the lab coat has been getting pretty good at telling us why life is really not as wondrous and mystifying as we would like to think. Of course, I am slightly jesting when I say that party-pooping is in every scientist’s job description (mind you, only slightly), but you do have to wonder how many more of our universe’s questions researchers will strive to explain with a labyrinthine equation or an arbitrary gene.

For the better half of this century, scientists have agreed and disagreed on the philosophical and scientific conundrum of physical beauty. Complex and inexplicable as it might seem, they have been trying for decades now to understand what makes something “beautiful”. Valiant attempts have been made at simplifying the problem in mathematical terms, and one subject that commonly crops up during these discussions is the relationship between beauty and symmetry. Note that, from now on, as I descend into the crux of this hotly contested matter, I shall defer from using the poetic term, ‘beauty’, and instead refer to it by its colder and more clinical name, ‘physical attractiveness’.

Symmetry can be seen throughout the natural world. Leaves and flowers are often found to be divisible by the sagittal plane. All animals, but for the sponge (no, SpongeBob Squarepants is not an anatomically correct depiction of this animal), are either radially or bilaterally symmetrical. Take a long hard look at yourself, if you haven’t already, and note the fact that you have a left side and a right side. Unless I just unwittingly alluded to a very tragic bodily malformation, I shall assume that both sides look virtually the same. These naturally recurring symmetries are apparently very crucial to sexual selection. Female zebra finches, for example, seem to prefer males whose characteristic chest plumage stripes are more symmetrical. This same predilection is apparent in other animals, such as swallows, swordtail fish and earwigs.

Upon observing these animal behaviours, many biologists have come to the conclusion that symmetry is a biological signal for health and viability, thus a contributing factor to physical attractiveness. This goes back to Dawkins’ The Selfish Gene, in which he made mention of the Parental Investment theory. I won’t bore you with the gritty details, but according to this theory, females are naturally liable to make a bigger investment in parenting a child. They carry the offspring for a certain period of time and are also commonly responsible for raising these offspring until they are deemed independent enough to survive on their own. To ensure that all of that effort is not wasted on a biologically disadvantaged brood, females must select only the healthiest and strongest males, in other words, the most “attractive” ones, to mate with. This brings about the many violent altercations that occur between males when vying for a certain female, and the fantastical courtship displays of birds such as the peacock.

But why would symmetry be considered more attractive by these animals, you ask. Well, the answer is, quite simply, it just is. When a feature that is usually symmetrical ends up being quite the opposite, something sinister is going on. Blatant asymmetry where it doesn’t belong could be a clear sign of mutations, disease or even parasitisation. Furthermore, an animal’s interest in symmetry might have something to do with the way it optically processes the world. To us humans, all the visual information scattered around us is transformed and brought together into one image. Under this logic, symmetry would be much more easier for our eyes to process than asymmetry. That is why animals who have evolved an optical organ similar to our own, such as birds, might be more keen to look at symmetrical bodies than asymmetrical ones. They are easier on the eyes, you could say.

When it comes to us humans, however, cultural and historical differences throw this clean and simple theory pretty much out of the window. Investigations into our perception of beauty are a hotbed of disputes and controversy. One such study conducted by Dahlia Zaidel at the University of California discovered a significant relationship between the perception of health and facial symmetry, but not between facial symmetry and attractiveness. In this study, a cohort of undergraduate students had to rate a series of head-on facial pictures either in terms how attractive, healthy or symmetrical they looked. Another slew of experiments presented perfectly symmetrical chimeras instead of normal pictures to their test subjects — these chimeras were created by dividing the facial picture in half and recreating a face from each half with its mirror image. You are not alone if you are confused as to how creating symmetrical chimeras from normal faces is supposed to uncover asymmetry. It’s like hiring a plumber to fix a water leakage which you have already fixed yourself.

Researchers that did find a significant relationship between symmetry and attractiveness have pointed out this flaw. They purport that facial symmetry is perceived to be more attractive within specific thresholds of normality, beyond which a face would be “too symmetrical” and thus appear abnormal. After all, many of our organs are designed to be asymmetrical. The hemispheres of the brain might seem identical at a glance, but ask any neurobiologist, and they’ll tell you how certain functions and features are mostly lateralised to one side. Even our faces follow this trend. This might just have you grimacing in front of your mirror for hours, but the left side of our face actually tends to be a bit larger and more expressive than the right. Taking into account these complications, the correlation between symmetry and beauty is perhaps too deeply layered for our current level of understanding.

If you do bother to look into the mammoth amount of research being conducted around this issue, it would seem as if every individual study contradicts every other previous one; there is never any general consensus, so for now, no scientist can definitely tell us whether symmetry really does contribute to physical attractiveness in humans. Yes, scientists might be good explaining away plenty of our world’s romantic enigma, but when it comes to beauty, even Richard Dawkins would be at a loss of words.

Eric John

(Image courtesy of Ray Ashley)

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  1. Adam Dawes
    October 30, 2010 at 12:02 — Reply

    What a fantastic blog! Nice work Eric, can’t wait for the next one!

  2. Al Derwent
    November 3, 2010 at 15:17 — Reply

    Two things: Some of us think that knowledge is beautiful and that learning something new is a beautiful thing. Secondly, if we ever do understand what makes a thing beautiful, I’ll wager all I have that that understanding will come from science.

  3. Phil
    November 4, 2010 at 19:11 — Reply

    I think it’s a mistake to identify “physical attractiveness” with “beauty”. The two aren’t even nearly the same thing, as philosophers who have tried to give an account of aesthetics have recognised since Plato. For what it’s worth, if we ever do discover what makes a thing beautiful, I’m betting it’ll come from the humanities: from philosophy, or literary theory, or theology.

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