Left – handed people get a lot of attention – from scientists as well as society in general. Is this because there are so few of them – only about 8%? And this figure apparently has remained stable through the eons – or at least as long as humans have walked the planet.
This last bit is based on findings by archaeologists; their methods may be open to question, but apparently, animals have paw preferences, too, but among animals the preferences are more evenly distributed in the populations (about 50% for each paw).
Read on to know more about the latest on this subject.
Putting the question to a scientist
When Chris McManus, professor of psychology and medical education at University College London was asked if being left – handed made individuals exceptionally smart, his answer was a simple ‘No’; this is, of course, based on all the available research.
But he further elaborates that you do find greater numbers of left – handers among mentally retarded or otherwise learning – disabled children.
To counter this is the observation that many gifted – people were left – handed – which included the likes of Albert Einstein, Isaac Newton, Benjamin Franklin, Charles Darwin etc. I maybe an exception (in being right – handed, I mean!)
What leads to left –handedness is still open to scientific discussion and debate, even though there are two very good hypotheses which explain nearly all the observations. Annette’s ‘right-shift’ theory and McManus’ ‘dextral/chance’ theory both postulate that handedness and cerebral dominance (see below) rely on certain genes. Annette’s theory differs in seeing a continuum of skill differences, in this case from the right – handed to the ambi-dexterous to the left – handed; McManus’ theory, on the other hand, would have you believe that there is a primary preference for right or left in individuals, and they differ in how much skill they have in using the other hand.
Both theories, however, accept that various other (environmental) factors (suspected factors include high exposure to testosterone in utero, or some kind of brain damage during birth – this should make all left – handers cringe!) also play a part. But for the most part the factors mentioned here have been debunked.
Lateralization or localization of function in the Brain
An interesting question – or facet to the issue is that the left side of the brain is predominantly involved in language. In the 1865 Broca showed that most people had language function localized to the left cerebral hemisphere. This was further expanded to the concept that the brain had specific areas which controlled specific functions, and this gave rise to the ‘localization of function’ approach in neurology, and became the foundation on which Neuroscience developed.
The theory has been modified subsequently; it is now understood that while specific areas of the brain have specific cognitive and other functions, the entire brain is used to perform most functions. In other words, for a majority of functions, the brain behaves like a network.
For example, in using language, the most important functions are localized to Broca’s Area in the Left Frontal Lobe and Wernicke’s Area in the Temporal lobe, along with their connections; but while communicating through language, the individual uses many more areas of the brain on both hemispheres.
It has been found that in 5% of right – handers and 30% of left – handers, language functions are localized to the right cerebral hemisphere.
This information is based on clinical studies on patients who had language difficulties from damage to areas other than those believed to be involved in language (such as occurs in Stroke), as well as Functional MRI studies on the brain.
Yet another very important aspect is hemisphere dominance; for a majority of people, the left – sided cerebral hemisphere is dominant for most functions – including language and handedness. The right hemisphere is considered to be related to creativity, emotions, and geo – spatial localization. A major part of the right hemisphere on the Parietal Lobe is concerned with the brain’s ability to control the body and the environment.
So the acts of dressing, map – reading, face recognition, and other similar functions which rely on the memory and manipulation of information of the body and the space around us – are largely localized to the right cerebral hemisphere.
About 90% of right – handed people are left-hemisphere-dominant. Among left – handed people, the left hemisphere is dominant in 50% of people. This is considered to be a reflection of the asymmetry of the cerebral hemispheres, though what evolutionary advantage this gave to human beings is not clearly understood.
A majority of the remainder have no particular dominance – which means that their brains are more symmetrical than the usual adult human. This symmetry may provide them with some advantages, for example in mathematical and musical abilities, as well as in creativity.
Left – handed advantage in sports
There are a large number of other observations which either support the hypothesis that left – handed people are gifted, or the opposite – that they are vulnerable or disabled. The fact remains that there are only 8% of left – handed people, and this gives them an advantage in certain team and individual sports.
For example, in cricket, a left – handed batsman has distinct advantage over the bowler who is more used to bowling to right – handed batsmen. The same thing applies to left – handed bowlers. In fact, team strategies are built on how many left – handed players are included in the team.
A recent study on around 2000 twin pairs with a genome – wide search for a specific gene for left – handedness failed to come up with a gene. It is still believed that several genes are involved in the development of left – handedness. It is further believed that several environmental factors also play central roles.
Take Home Message
So it is true that left – handed people have several advantages over right – handed people; but before you go to town claiming superiority, please bear in mind that there may be a few disadvantages as well!
One way or the other, left – handedness is rare in the population, and deserves to be celebrated; to this end, August 13th has been declared as International Left-Handers’ Day!