Deciphering Left Handedness 101
At first sight it seems a fairly simple matter to say what is meant by being right-handed or left-handed, but a little consideration soon shows that this very simplicity is a source of difficulty. We say that a person is right-handed if he for preference uses his right hand rather than his left to carry out the more skilled kinds of movement and is more skillful at such movements with his right hand than with his left. The converse is true of a left-handed person. Handedness, therefore, is nothing absolute; it is a question of degree, a preference based upon a skill with which the two hands are used. Moreover, it takes no account of the actual degree of skill present, nor does it imply any cause for the difference. From Charlemagne to Leonardo Da Vinci, the ‘left-handedness versus the right’ debate can be traced back deep into history. Left handedness has been the topic of a not-so-silent debate, one that has only recently ceased to be a liability. A journey through the pages of a Medieval text will show us that left-handed people lived in constant fear of being branded as warlocks, burnt alive for practicing the deadly art of witchcraft. Though the general attitude towards left-handedness is significantly less hostile, the stigma still exists today in parts of Asia, despite the knowledge of how the epigenetic gene manifests in various people. However, there has always been an uncontested boon of being left-handed: Sports. Left-handed people have an advantage in sports that involve aiming at a target, because their opponents are be more accustomed to a largely right-handed majority. The result? A large representation of left-handed sports persons, especially in interactive sports like tennis, football, basketball et al. This is where the story begins.
”Left-handed people can think quicker when carrying out tasks such as playing computer games or playing sport, say Australian researchers.”
In gesture and in manipulation the hand represented in that hemisphere takes the lead, and it is the dominant hand which converts thought into symbols in writing. Thus, handedness connotes a much richer series of functions in man than in the ape. It is, as it were, raised to a higher power and is an integral part of the activity of the dominant hemisphere. Thus we are left with the question why the left hemisphere is commonly the major one. The genetic explanation of this is that left-hemisphere dominance is dominant also in the mendelian sense, whereas dominance of the right half of the brain is usually inherited as a recessive. Attempts have been made to discover some evolutionary advantage in right-handed- ness which would tend to favor the right-handed by natural selection.
Study leader Dr Nick Cherbuin from the Australian National University measured transfer time between the two sides of the brain by measuring reaction times to white dots flashed to the left and right of a fixed cross. Tests in 80 right-handed volunteers showed there was a strong correlation between how quickly information was transferred across the left and right hemispheres and how quickly people spotted matching letters. But when the tests were repeated in 20 left-handed volunteers, the researchers found that the more left-handed people were, the better they were at processing information across the two sides of the brain. Extreme left-handed individuals were 43 milliseconds faster at spotting matching letters across the right and left visual fields than right-handed people.
To conclude, yes, left-handedness comes from dominant and recessive genes, but there are several cultural and environmental factors that affect the same, that only further in-dept research that divulges into the topic can prove.
Interest in exploring more about the science of Left-Handedness and the genetics associated with it? Check out our article on ‘The Genetic Markers Associated With Left-Handedness’ for a quick read on left-handedness among the world’s population today.