The body of the human being, like that of almost all the bodies that populate the set of animal life forms, follows certain symmetry patterns
We have two arms, two legs, two eyes and a nose in 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 very similar ways both to the left and to the right.
As you might expect, these same rules are reflected in the shape of our brain. We have two cerebral hemispheres, each on the left and right, which are somewhat like mirror images of each other… at least to the naked eye. In reality, both hemispheres are very different at the cellular level and, in fact, they are responsible for different processes. We all know that idea that says that the right hemisphere is rational and analytical, while the right hemisphere 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 than its opposite side, since each of these halves It is related to one of the two hemispheres of the brain For example, almost all of us have a dominant hand and consider ourselves right-handed, since we use our right hand 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 to be true for their eyes or legs. These are cases of crossed laterality.
Cross laterality, homogeneous laterality and dominance
Normally we talk about homogeneous laterality, because people whose dominant hand is on one side tend to have the dominance of the rest of their members and senses aligned in that half. Therefore, when we talk about 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 crossed or homogeneous laterality.
In any case, crossed laterality is another 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 based on the nerves that the causes of one or another type of laterality must be sought, and this can also be defined by the areas of the body that it affects. In that sense, there are different dominance classes 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 foot or the other 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 aiming with gaze.
Why does crossed laterality exist?
The nervous mechanisms by which one or another type of laterality occurs are not very well known, nor why sometimes there are cases of crossed laterality when the majority is that homogeneous laterality exists. In any case, crossed laterality would be proof that there is no great 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 cause some problems when coordinating parts of the body whose dominance is discordant, such as when writing. There is a lack of research in this regard, but it is considered cautious take into account crossed 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 determined only by genetics, but also learned behavior influences it culture, habits, etc.
Cross laterality is not an exception to this rule, and therefore one can learn to mitigate the effects of a very extreme dominance to also use the homologous body part in the other half, going on to speak in this case of forced laterality.
