Laterality and crossed laterality: what are they?
The body of the human being, like that of almost all the bodies that populate the set of animal life forms, follows 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 disposition of almost all of our organs. We are adapted to perceive and act in a very similar way both to the left and to the right.
What are laterality and crossed laterality?
As expected, these same norms are reflected in the shape of our brain. We have two cerebral hemispheres, each one on the left and right , which are something like mirror images of each other ... at least with the naked eye. In fact, 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 the right hemisphere is rational and anal, 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, almost everyone has a dominant hand and we consider ourselves right-handed, since we use the right hand for almost everything. However, this fact does not mean that we have a half of the body that is entirely dominant. Interestingly, it is possible for a person to have a dominant right hand, but for the opposite to happen with their eyes or legs. These are the cases of crossed laterality.
Cross laterality, homogeneous laterality and dominance
Normally we speak of homogeneous laterality, because the people whose dominant hand is that of one side tend to have aligned in that half the dominance of the rest of their members and senses. 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 if there is a crossed or homogeneous laterality.
In any case, crossed laterality is another form of laterality, and the existence of one or the other type is a consequence of the functioning of our nervous system. That 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 that sense, there are different dominance classes which 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, stay on one leg, etc.
- Auditory Dominance : tendency to use more one ear or the other to listen, put on an earphone, etc.
- Ocular or visual dominance : defined by the dominant eye at the time of aiming with the look.
Why is there cross laterality?
They do not know very well the nervous mechanisms by which one or another type of laterality occurs , nor why sometimes there are cases of crossed laterality since the majority is that there is homogeneous. In any case, cross-laterality would be proof that there is no large planning center responsible for coordinating the different dominances or, if it exists, its function or is essential.
In any case, it is currently believed that cross-laterality could give some problems when coordinating the parts of the body whose dominance is discordant, such as at the time of writing. Research is lacking in this regard, but it is considered cautious take into account cross-laterality as a risk factor in the appearance of learning disorders in children .
In any case, since 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 the learned behavior influences it , culture, habits, etc.
Crossed laterality is not an exception to this norm, and therefore one can learn to mitigate the effects of a very extreme dominance to also use the homologous part of the body in the other half, going on to speak in this case of forced laterality.
