Truths and lies about lefties

08/02/2020

Truths and lies about lefties
Many people consider that the left-hander predisposes to die earlier, to suffer more illnesses or to be of an introverted nature. But do these assumptions have any scientific basis?
Written by: Editorial Diario del Huila | August 14, 2019
By Sergio Parra
For centuries, the left side has been identified with misfortune and even evil. Not surprisingly, sinister (‘sinister’) is a Latin word that means ‘left’. However, the opposite side, the law, was considered synonymous with skill, virtue and justice. Horacio exclaimed "Ego laevus!" (How silly I am!), Which, literally translated, means ‘How lefty I am!’. Muslims, meanwhile, use the right hand to eat and the left hand, to wash, especially the intimate parts. And the idiom having two left feet is used to indicate that someone is very clumsy, especially dancing.
Although these manifestations are merely cultural, 90% of people prefer to use the right hand, a proportion that has remained relatively stable throughout history. Therefore, the left-hander has been the subject of countless myths that have often served to repudiate her even more.
Myths
Among the most entrenched are the following: The laterality is reflected in the fact that one of the two symmetrical parts of our body predominates over the other when carrying out most of the activities: left-handed people have left laterality; right-handed, right.
There is still no unanimity about the origin of this trend. It could be a genetic condition - inherited - or congenital - for example, as a result of exposure to high levels of testosterone in the womb. Be that as it may, after analyzing all the studies on this subject, Phil Bryden - a fundamental figure in the investigation of the lateralization of the brain or division of labor between the two hemispheres and Chris McManus - professor of Psychology at University College London - found a significant statistical correlation: of the 70,000 children studied, those who had both right-handed parents showed a 9.5% probability of being left-handed; if one father was left-handed and the other right-handed, the probability amounted to 19.5%; and if both partners used the left hand, the probability reached 26.1%. However, it does not necessarily follow that we are faced with a genetic phenomenon, because families can also instill culturally left-handedness.
Newborns are ambidextrous
It is generally accepted that newborns are ambidextrous up to eighteen months and two years, which is where a lifelong trend is established. However, some studies have detected laterality in fetuses, such as the one published by Peter G. Hepper, a fetal behavior specialist at Queen’s University in Belfast (Northern Ireland). After analyzing more than a thousand fetuses by ultrasound, Hepper suggests that the preference of the hand occurs when the fetus is ten weeks old: 90% of them sucked more on the right thumb.
Ten years later they were able to confirm that all who had sucked this thumb in the womb were right-handed; and that 67% of those who sucked the left were left-handed.
Neuroscience has traditionally considered that the right hemisphere of the brain is where creativity resides; and as this side controls the left hand, it has been argued that left-handed people are more creative. To reinforce this idea, lists of artists who have had this natural tendency have been drawn up, and in which they appear from Leonardo da Vinci to Paul McCartney.