Why does each person have preferences when it comes to using a part of their body?
The body of the human being, like that of almost all the bodies that populate the set of forms of animal life, follows patterns of symmetry.
We have two arms, two legs, two eyes and a nose on our central axis, and the same logic is repeated in the arrangement of almost all of our organs. We are adapted to perceive and act in much the same way to both the left and the right.
What are laterality and crossed laterality?
As you might expect, these same rules are embodied in the shape of our brain. We have two cerebral hemispheres, each on the left and right, which are something like mirror images of each other … at least with the naked eye. In reality, both hemispheres are very different at the cellular level and, in fact, are responsible for different processes. We all know that idea that says that the right hemisphere is rational and analynic, while the right is emotional and responds in a special way to music.
These subtle variations mean that for certain tasks we have one side of our body that responds differently to its opposite side, since each of these halves is related to one of the two hemispheres of the brain. For example, most of us have a dominant hand and we consider ourselves right-handed, as we use our right for almost everything. However, this fact does not mean that we have one half of the body that is entirely dominant. Interestingly, it is possible for a person to have a dominant right hand, but the opposite may be true for their eyes or legs. These are the cases of crossed laterality.
Cross laterality, homogeneous laterality and dominance
Normally we speak of homogeneous laterality, because people whose dominant hand is the one on one side tend to have the dominance of the rest of their limbs and senses aligned in that half. Therefore, when we speak of laterality we are referring to the different dominances that exist in a person, and the set of these dominances will be what defines whether there is a cross or homogeneous laterality.
In any case, crossed laterality is one more form of laterality, and the existence of one type or another is a consequence of the functioning of our nervous system. This means that it is in the interconnections of our different parts of the body from the nerves where the causes of one or another type of laterality have to be sought, and this can also be defined by the areas of the body that it affects. In this sense, there are different classes of dominance that serve as criteria to define the type of laterality:
- Manual dominance: defined by the dominance of one or the other hand when picking up objects, writing, touching, etc.
- Foot dominance: defined by the dominance of one or the other foot to kick, kick a ball, stand on one leg, etc.
- Auditory dominance : tendency to use one ear or the other more to listen, put on a headset, etc.
- Ocular or visual dominance: defined by the dominant eye when looking at it.
Why is there cross laterality?
The nervous mechanisms by which one or another type of laterality occurs are not very well known, nor why sometimes cases of crossed laterality occur, since the majority is that there is homogeneous. In any case, cross-laterality would be proof that there is no large planning center in charge of coordinating the different dominances or that, if it exists, its function or is essential.
In any case, it is currently believed that crossed laterality could give some problems when coordinating the parts of the body whose dominance is discordant, such as when writing. Research in this regard is lacking, but it is considered cautious to consider cross-laterality as a risk factor in the appearance of learning disorders in children.
In any case, as the system of connections between neurons on which dominance is based is highly plastic (that is, adaptable according to our learning and experiences), laterality is not only determined by genetics, but behavior also influences it. learned, culture, habits, etc.
Cross laterality is not an exception to this rule, and therefore it is possible to learn to mitigate the effects of a very extreme dominance to also use the homologous part of the body in the other half, in this case going on to speak of forced laterality .