Isuri Upeksha Wimalasiri
General Sir John Kotelawela Defence University, Kandawela Estate, Ratmalana, Sri Lanka (Fall 2017)
Most human beings, some 85% to 95%, are right-handed, and the remainder consists mainly of left-handers and a negligibly small number of ambidextrous people. Hand orientation is decided during intrauterine life, but if a child shows hand preference before the age of eighteen months this it is considered abnormal and pointing towards a weakness in the opposite side of the hand or body.
Handedness is generally defined as the hand used for writing. Scientifically it is defined as the hand that is more precise for manual tasks and performs such tasks with greater dexterity. Sometimes, handedness is used synonymously to define the preferred hand regardless of its ability.
According to studies, 96% of right-handers and 70% of left-handers have as dominant hemisphere the left. In 4% of right-handers and 15% of left-handers the dominant hemisphere is the right. In the remaining 15% of left-handers, there is no clear lateralization of the brain. This hemispheric specialization is directly related to handedness1.
In humans, one of the two cerebral hemispheres is associated with categorization and symbolization and thus is often called the ‘dominant’ or ‘categorical’ hemisphere. The other cerebral hemisphere, also called the ‘non-dominant or representational hemisphere, is specialized in spatiotemporal awareness. Accordingly, dominant hemisphere is associated with fine motor skills, assessment, patterns, methodical and systematic activity; and the non-dominant hemisphere is associated with spatial and visual skills, imagination, music, and artistic ability.
Several studies have suggested that left handedness is multi-factorial, genetic and environmental, but it also appears in families where immediate members are not left-handed. According to the Geschwind theory, high levels of testosterone before birth could favor the child developing a left-hand orientation. This is because high testosterone levels suppress the growth of the left cerebral hemisphere, causing more neurons migrate to the right hemisphere, which then becomes established as the center of language and handedness. As the right hemisphere controls the left half of the body2, the fetus is more likely to become left-handed, a theory now accepted worldwide and supported by the fact that the majority of left-handers are males.
In 2007 researchers discovered that specific alleles of at least one of three single-nucleotide polymorphisms upstream of the already known LRRTM1 gene were linked to left-handedness3. Twins theory explains that left-handed individuals were originally part of an identical twin pair, with the right-handed twin fetus failing to develop early in development4. Although Australian researchers have debunked the related vanishing twin theory, it remains unexplained why twin children have a high frequency of left-handedness/right-handedness in the pair. People with long-term impairment of the right hand are more likely to become left-handed, even after their right hand heals.
Since handedness affects many aspects of a person’s life (household chores, career, leisure activities, thinking and even social standing) living in a world designed for the comfort of the right-handed majority is an inherent struggle for the left-handers. Yet being a minority might confer advantages not obvious at first sight.
In everyday life, left-handers encounter challenges that depend on many factors such as occupation, preferred leisure activities, etc. Since most people are right-handed, everyday items are produced to be used with the right hand. Tools, game equipment, or musical instruments must be specially ordered for left-handed use, if available at all. Left-handed people may find right-handed tools difficult or uncomfortable to use unless they have learned to adjust. This applies even to even simple tools that require little dexterity, such as scissors.
While writing may necessarily remain a left-handed function which requires a considerable degree of dexterity, other two-handed functions may well be done in a right-handed manner. However, left-handedness will always be far more apparent in one-handed operations.
Left-handed instruments have been introduced to the world of music. Left-handed guitars are manufactured as an alternative to using a flipped around right-handed guitar. Christopher Seed, a left-handed pianist, invented the first left-handed piano that is reversed so that the deepest notes correspond to the rightmost keys instead of the leftmost.
In some countries, classrooms and offices are designed to maximize the use of natural light by placing desks so that the windows are on the left. This can be inconvenient for left-handers because the shadow of their left hand with the pen makes it harder to see the text being written.
In the past left-handed children were often forced to use their right-hand during their formative years because of the negative cultural impact. In many cultures, the left-handedness was historically deprecated. The Latin word sinistra, originally meaning “left”, took on meanings of “evil” or “unlucky”. The right hand has historically been associated with skill: the Latin word for right-handed is dexter, as in “dexterity”, meaning manual skill. Eating with one’s left hand has been considered immoral, especially in South-East Asia, probably because right-handed people tend to use their left hand to clean themselves after defecation or urination5. Since these actions are considered unclean, the hand used is also considered unholy, and sadly this was or still is the case.
Sometimes even kings and queens could not escape the general publics’ prejudice against left-handedness. The best example of this is King George VI, who in his early career was unable to deliver public speeches and was considered unfit to be a king because of a pronounced stuttering attributed to an unhappy childhood due to his left-handedness.
Left-Hander Syndrome is a condition seen in left-handed people who are coerced to write with their right hand, this thus causing a state of mental confusion. Statistics show that left-handed people are more likely to succumb to accidents, fatalities and other injuries arising from such confusion,6 largely because so many utilities are designed to accommodate the right-handed majority. Studies show that there are about 13% left-handers among people in twenties and fewer than 1% left-handers among those in eighties. This finding may be accounted by there being more pronounced socio-cultural pressure on left-handed people in the past than at present7.
Left-handers, however, do have some advantages over right-handed people. They tend to be more athletic and have with a slightly higher degree of spatial awareness. There is a disproportionately larger number of left-handers in some specific groups such as mathematicians, sculptors, architects, painters, musicians, actors, as well as famous army commanders and rulers.
Left-handers’ brains often handle music more easily, but their linguistic ability seems to be lower than that of right-handers. Bob Dylan, a left-hander, wrote the music for “Blowin’ in the Wind” in less than five minutes, but it took him a month to write the lyrics.
The advantage seems to persist in players in one-on-one sports such as tennis, boxing, fencing or judo because the left-hander plays 90% of his games against right-handed opponents and is well practiced at dealing with this asymmetry. The right-hander plays 90% of their games against other right-handers and thus is less practiced when confronted with a left-hander. When a left-hander plays another left-hander, they are both likely to be at the same level of practice as when right-handers play other right-handers. This explains why a disproportionately high number of left-handers are found in sports where direct one-on-one action predominates8.
It is said that left-handed people have an advantage in combat for the same reason as in sports (combatants would encounter left-handed opponents less frequently). This tactic is well-known to combat sport fighters and was employed to world-record effect in a boxing match on November 4, 1947, when Mike Collins, a natural left-hander, emerged from his corner in a right-handed stance before suddenly shifting left and delivering the fight’s first and last punch, knocking out opponent Pat Brownson in four seconds.
In conclusion, it is apparent that left-handedness confers both opportunities and obstacles. Since left-handers will thrive and feel more at ease when they can use their natural handedness, parents or teachers should refrain from urging left-handed children to swap their natural handedness. Instead, more opportunities and a wider variety of left-handed tools and equipment should be made available. The general public especially those who belong to cultures where left-handedness is shunned upon or considered an anomaly, should change their viewpoint and welcome the perspective that left-handedness is a normal variation.
- Willems, R.M., Toni, I., Hagoort, P. and Casasanto, D., 2009. Body-specific motor imagery of hand actions: neural evidence from right-and left-handers. Frontiers in Human Neuroscience, 3.
- McManus, I.C. and Bryden, M.P., 1991. Geschwind’s theory of cerebral lateralization: Developing a formal, causal model. Psychological bulletin, 110(2), p.237.
- Ocklenburg, S., Beste, C. and Güntürkün, O., 2013. Handedness: a neurogenetic shift of perspective. Neuroscience & Biobehavioral Reviews, 37(10), pp.2788-2793.
- Sun, T., Collura, R.V., Ruvolo, M. and Walsh, C.A., 2006. Genomic and evolutionary analyses of asymmetrically expressed genes in human fetal left and right cerebral cortex. Cerebral cortex, 16(suppl_1), pp.i18-i25.
- Budryte, D. and Boykin, S. eds., 2017. Engaging Difference: Teaching Humanities and Social Science in Multicultural Environments. Rowman & Littlefield
- Coren, S., 2012. The left-hander syndrome: The causes and consequences of left-handedness. Simon and Schuster.
- Bryden, M.P. and McManus, I.C., 1992. Dispelling myths about left-handedness. International Journal of Psychology, 27(3-4), pp.400-400.
- Grouios, G., Tsorbatzoudis, H., Alexandris, K. and Barkoukis, V., 2000. Do left-handed competitors have an innate superiority in sports?. Perceptual and motor skills, 90(3_suppl), pp.1273-1282.
Image obtained from https://www.flickr.com/photos/msgp02a/4881002479/
ISURI UPEKSHA WIMALASIRI, MBBS, completed her secondary education at Devi Balika Vidyalaya, Colombo. She was among the top 10 students of the country at GCE Ordinary Level Examination -2004 and entered medical college after GCE Advanced Level- 2007. She graduated from Faculty of Medicine, University of Sri Jayewardenepura in 2014 with MBBS (Honours) and Distinctions in Psychiatry and Parasitology. She completed her internship at Lady Ridgeway Hospital for Children and Castle Street Hospital for Women, two leading hospitals in Sri Lanka as well as in South Asia. She is currently working as a lecturer in Physiology at Faculty of Medicine, General Sir John Kotelawala Defence University.