Right-handed and left-handed: this is how biological laterality works

The biological laterality it is the predominance of one side of the body over the other. Generally, it is classified according to the predominance of one hand over the other since it is the most visible, but it is necessary to take into account also the lower extremities and the sensory organs of sight and hearing.

In this way, depending on the side that predominates, right or left, this distinguishes the laterality of people. Most of us are right-handed, that is, we manage the right members and bodies better. Lefties handle the members on the left side better. There are also the ambidextrous people who are people in whom there is no clear predominance and use both sides indistinctly.


In people with crossed laterality, one side is predominant in the extremities and the other in sensory organs and although they are few, they exist. For example, for a child to kick the ball with the left foot and throw it with the right hand. Trained lefties are those who have been forced to use their right hands. They carry many added problems, although there are very few trained lefties.

Biological laterality gives rise to left-handed and right-handed

The biological cause of cerebral laterality is that the brain is formed by two identical, walnut-shaped hemispheres, so that, depending on which side develops the most, this defines laterality. If the left hemisphere is the most developed, it will dominate the right side, giving rise to the "right-handed". If it is the right, it will dominate the left side giving rise to the "lefties". And both the left-handed and the right-handed express themselves corporally. For example, we can see which leg we usually cross over the other, which arm covers the other when we cross our arms, in which ear we usually place the phone to speak, with what foot we started to swim or with what foot we started to climb the stairs.


The predominance is defined around six years of age. This is so because during that time it is the ideal sensitive period in which the brain establishes millions of nervous connections to develop all the capacities that can be. In fact, at two years of age, both hands are still used indiscriminately and at four years old it is when a predominance starts to show, establishing laterality around six years.

How is our brain: this is how we are according to the predominant side

The brain is composed of two halves responsible for different but coordinated functions. The two halves, the cerebral hemispheres, look identical and are joined by millions of nerve fibers called the corpus callosum. They send messages to the hemispheres, messages that are different for one or the other.

The left hemisphere, predominant in right laterality, controls speech, writing and abstract thinking. The right hemisphere, predominant in the left laterality, controls non-verbal memory, emotions and concrete thought.


We have two hemispheres with different competences and functions. In summary, one could say thatThe right is an analog hemisphere, which handles concepts, which have a global vision. The left one is logical, analytical, accountant, mathematician and retailer. That is why they need to be well connected, to understand that "table" is that tangible thing associated with the concept itself.

Marisol Nuevo Espín

Video: Why Are People Left-Handed?


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