Our eyes cannot help but love symmetry to find in what we see. From the outstretched plumage of the peacock to the petals of a tulip, we see symmetry as beautiful, and as a result, many great works of art and architecture rely on symmetry, as well as the golden ratio at its core.
We look at people in the same way, and when you think about people that you find beautiful, they tend to be very close to symmetrical, and we are subconsciously unsettled when they are not.
Why is this? Why do we value symmetry so much to the point that people will have facial symmetry fillers to help achieve a more desirable look?
The answer is somewhat complex, and there are many different proposed answers.
One of the biggest reasons is that symmetry is elegantly simple. Our minds are almost too good at recognising patterns, and symmetrical designs are pleasing to the brain because they are easy to understand.
One example of how our brains work like this can be seen with the Kanizsa Triangle. This optical illusion consists of three v-shaped lines and three circles with a v-shaped chunk missing from them. However, our brains see it as a white triangle overlapping the lines of another triangle.
Another somewhat misguided belief is that there is a connection between symmetry and health, which was commonly touted by evolutionary psychologists but has since been debunked in various studies.
This suggests that our love of symmetry is more aesthetic and more based on how nature typically is symmetrical too.
However, there is also too much of a good thing. Several studies of faces designed to be completely symmetrical have highlighted how this can look less pleasing or even uncanny, so a small level of asymmetry combined with a general symmetry in a face is the hallmark of beauty to many.