In the natural world, it doesn’t really matter whether something is facing the left or the right direction.
Leaves, butterflies, trees, flowers, or even humans don’t look much different from the left side or the right side.
So, from an evolutionary perspective, there has never been a reason for the brain to spend energy on telling left from the right.
For example, if the fruits on the left side of the tree were poisonous, while those on the right were healthy, we would have definitely developed a clear perspective on the orientation.
But since they are not, our brains don’t care.
Now, most of the things that require us to make sense of the left-side or right-side are man-made.
Letters are man-made, and the direction they are facing gives them a completely new meaning.
For example, ‘p’ changes to ‘q’ in the mirror and if we reflect upside down, ‘p’ becomes ‘d’ and then left to right again it is ‘b’.
Compare this to a cat – no matter which angle we see it from, it remains a cat; so, the change of meaning by the change of direction is unnatural for our visual system.
Children under the age of 7 write backward because of the tension between a natural tendency for our brains to treat mirror-images as equivalent, and a culturally imposed need to distinguish between them for written language.
This is also evident from the fact that nobody teaches kids to write backwards – it comes ‘naturally’.
Even adults can experience this tension – if we paste a piece of paper under the table or against our forehead and try to write on it, most of us will struggle to find the writing fluency we otherwise have.
