LOOKING in the mirror, you may notice a slight imbalance in your features – a leftward curve of the nose, a wrinkle that only appears under one eye or an ear that is slightly higher than the other.
For centuries, this lack of perfect balance was thought to detract from our beauty, and you can find many services, from photo filters to cosmetic surgery, that aim to “correct” it. Yet asymmetry is built into the human body and brain – and for good reason. What’s more, new research suggests that it has little influence over our appeal to others.
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Let’s start with the . For most people, the heart, stomach and spleen all fall to the left of the spinal cord, while the liver and gall bladder fall to the right. This makes more efficient use of the space in our thorax and abdomen, compared with a structure aligning every organ with the spine.
Why are human brains asymmetrical?
How about the brain? Its two hemispheres may appear to be reflections of each other, but the corresponding regions on each side have different responsibilities. You will have noticed the effects of this on your movements. If you are right-handed, that is because the left hemisphere of your brain – which is wired up to the right side of the body – has become slightly more specialised in the fine muscle control of your fingers, giving you greater dexterity in that hand.
It may surprise you to discover that this “lateralisation” can be found in many other behaviours. Most of us have a dominant ear or eye, for example (see “Are you left or right-eyed?“, below). “If you peek through a keyhole, then the majority of people would use their right eye, regardless of where the keyhole is – whether it is on the left or on the right side of the door,” says at Ruhr University Bochum in Germany.
He argues that . If, when growing up, we use both hands for dexterous tasks, then the effects of that training will be split across the two hemispheres. If, however, we only use one hand, then the effects of that training will be focused on a single hemisphere – leading to quicker neural specialisation and faster progress. The same logic applies for sensory processing. “The more we train our visual cortex to see certain patterns in complex pictures, the better we get at it,” says Güntürkün. And you maximise this advantage by ensuring that the majority of the practice goes into developing just one side of the visual cortex.
Are symmetrical faces more attractive?
How about facial asymmetries? At conception, our genomes plan for our external features to develop in perfect proportion to each other. However, we all face stresses – such as illness – that can create tiny perturbations in our growth that deviate from this blueprint. These result in the slight asymmetries that we observe in the mirror.
According to the “good genes” hypothesis, people with better genetic health – governing their immune system, for example – develop fewer imperfections during development, with more symmetrical faces. Facial symmetry should therefore be more attractive to people looking for a mate with good genes to pass on to their offspring. The hypothesis has become a law unto itself after a lot of early research seemed to support it.
However, none of these predictions has stood up to the scrutiny of recent research. doesn’t seem to be related to physiological factors like immune function and – even more damningly – it . In one experiment, at Swansea University, UK, and at Tilburg University in the Netherlands asked participants to rate photos of people with various levels of facial asymmetry. “We couldn’t find any relationship,” says Jones.
He points out that preferences will vary greatly from person to person, but symmetry doesn’t seem to be an important factor for most people. Beauty, it seems, really does lie in the eye of the beholder.
Are you left or right-eyed?
Put your arms out in front of you and make a triangle with your thumbs and forefingers. With both eyes open, centre this triangle around a distant object – a clock or a doorknob, say. Close your left eye. If the object barely moves, then your right eye is dominant. If the object is no longer framed, then the left eye is top dog. Your brain combines information from both eyes to help you perceive the world, but preferentially uses information from one eye over the other – .
