Why do young children write in mirror writing and how is this related to the brain?

Imagine sitting in a taxi on a cold rainy day. Vapor accumulates on the window and suddenly you realise that the girl of your dreams is sitting in the adjacent car, or perhaps it is an old friend you have not met in many years. You try to communicate with them and give them your phone number or email address by writing it on the window. To make the message legible to them you must write in mirror writing. Will you be able to convey the message before the light changes and the opportunity is lost forever?  

Mirror writing is formed by writing in reverse to the regular direction of writing, such that the letters are written in mirrored form, appearing normal when reflected in a mirror. Such writing can be either voluntary, as in the example of Leonardo da Vinci, who used mirror writing in his private notes, or involuntary, such as in cases of damage to certain areas of the brain, degenerative brain disease or developmental problems, as well as in young healthy children who are making their first steps in writing.

Mirror writing in Leonardo de Vinci’s notes | Source: Wikipedia
Mirror writing in Leonardo de Vinci’s notes | Source: Wikipedia

How is mirror writing possible and why is it especially common in children? Is the phenomenon related to a reversed perception of the letters, or could it be that the perception is correct but rather that the problem is in the motor execution of writing?

The Perceptual Explanation

According to this approach, every word or image we recognize is represented and stored in the dominant part of our brain, where our speech and language centers reside (in most people it is the left hemisphere, i.e. the left side of the brain), while the reverse form of that same word is represented in the other side of the brain. The reverse representation is normally repressed and does not affect our functioning, except in cases where the mechanism of repression of the reverse representation is damaged, as a result of injury or illness. A similar situation can occur when none of the hemisphere is dominant yet, as is the case with children whose brain dominance has not been established yet.

The two hemispheres of a sheep’s brain | Image: Wikipedia, aaronbflickr
The two hemispheres of a sheep’s brain | Image: Wikipedia, aaronbflickr

The Motoric Explanation

This approach refers to the motor basis of the writing process. Each letter, word and sentence we write has a precise motor program that includes instructions for the operation of the various muscles at the right timing and in the right direction. In people with a dominant right hand, the motor plan for regular writing is usually located in the left hemisphere, while the plan for mirror writing is located in their right hemisphere. 

The left part of the brain is usually the one to dictate movements associated with writing, while the right side is repressed, and thus the motor program is implemented into normal writing. Similar to the perceptual approach, if the repression mechanism is impaired or in case of a defect in the left hemisphere, the right part of the brain takes over, activating the reverse motor plan that produces mirror writing. 

According to this explanation, in young children whose brain dominance has not been established yet, it is possible at times to activate the reverse motor program, controlled by the right hemisphere, which is why mirror writing is so common among them. 

Another motor explanation is based on the assumption that movements we make from the midline of the body outwards, i.e. from the ribs outwards, are more comfortable for us and more accurate than movements made in the opposite direction. Thus, the right hand will mostly move from left to right (from the center of the body outwards) and the left hand will move from right to left (also from the center outwards). 

This principle can be used to explain why mirror writers in Western countries are mostly left-handed. Western languages, such as English, are written from left to right, but when using your left hand it is much more natural to write in the opposite direction - from right to left. In order to produce a readable message, left handed people suppress this natural tendency and get accustomed to writing from left to right, like right handed people.  

In contrast, in young children who are taking their first steps in writing, the skill of suppressing natural tendencies of movement is not sufficiently developed. They do not yet feel confident in the direction of writing and often experiment with writing using their non-dominant hand. Thus, they sometimes tend to start writing in the opposite direction and continue to mirror write without correcting themselves. 

What happens then in the Semitic languages, which are written in the opposite direction - from right to left? In Hebrew and Arabic, for example, right handed writing is performed from the outside to the center of the body, supposedly the opposite of the natural and comfortable movement. Is there a difference in the prevalence of mirror writing between Semitic and western languages? 

Unfortunately, research in the field is scarce and therefore this question is difficult to answer. Several studies claim that mirror writing is more common in people who use languages written from right to left, since they are normally required to make a movement that comes in contrast to the natural direction of movement from the center of the body outwards. An interesting publication was that of a rather unique case of a man who wrote in mirror writing using his right hand in Hebrew, but not in French. 

A common myth must be dispelled with respect to mirror writing in children. Such writing was attributed in the past to delayed mental and motor development. Recent studies show no differences in intelligence between children who write in mirror writing and children of the same age who write in the regular direction. In most cases it is part of the normal developmental process of acquiring writing skills, a transitional stage between illiteracy and correct writing.  

When learning to use a faucet, a child must simultaneously learn an action and its opposite counterpart - of turning the faucet on and off again - two essential actions. Likewise, in the acquisition of writing skills there is room for both forms: the ordinary and the mirrored. The difference is that in writing, which serves for communication between an individual and the environment, the mirrored form is useless and it is therefore discarded once the child learns both forms and understands the importance of using the accepted form in the society in which he lives.