Lateralisation of human functions

By Ng Wee Loon

INTRODUCTION
“Human manual lopsidedness is fast becoming a major theme of inquiry in primatology, anthropology, genetics, neurology, developmental psychology, and linguistics” . This statement by Frank R. Wilson in his book “The Hand” aptly sums up the attention given to the studies of lateralisation in today’s scientific world. We now know that the human brain is made up of two different sides, termed as “hemispheres” that perform different functions. The left hemisphere is connected to the right side of the body and conversely, the right hemisphere is connected to the left side of the body. Each hemisphere performs specific functions and that is what we mean by “lateralisation”. The reason why lateralisation is given so much attention now is because “the development of lateralised function has been suggested as important to normal language, cognitive, social, emotional, perceptual and motor development, as well as to the early detection of certain kinds of abnormal development and disabilities” . One of the most pronounced forms of lateralisation is “handedness”, the dominance of either the left or the right hand in performing most of the activities. Several theorists have attempted to explain the prevalence of the right hand in human beings and some of their theories will be highlighted in this paper. The possible disadvantages faced by the minority left-handed population and the reasons behind these disadvantages will also be discussed. Lastly, the paper will explore the relationship between child development and lateralisation.

THE PREVALENCE OF RIGHT-HANDEDNESS
“Handedness is uniquely human” and “we alone exhibit a strong preference for the use of the same hand – left or right – in a variety of manual task” . Dr. Michael Corballis from the Department of Psychology at the University of Auckland mentioned in his book “Human Laterality” that there had been discussions as to the reasons for the prevalence of right-handedness, particularly the argument as to whether it is a “biological or cultural endowment” . According to him, the “bulk of the evidence suggests that our predominant right-handedness is not shaped by culture, but rather that our ‘right-handed world’ is a consequence of biological right-handedness.” Frank R.Wilson, who raised examples of the biological need for single strong hand preferences both in ancient times and in more modern researches, complements his view.

DISADVANTAGES FACED BY LEFT-HANDERS
Disadvantages faced by left-handers come from both the social stigma associated with them and from negligence shown to them in a “right-handed world”. Society often attach its own customs and beliefs to the hand and often certain words with negative connotations such as “profane”, “sinister”, “unlucky” are implicitly linked to the left hand. This results in left-handers being treated differently and often children discovered with left-handedness are made to convert to right this “defect” .
Other than cultural and social disadvantages, “Joseph Bogen, a neurosurgeon has also argued that the current emphasis on the acquisition of verbal skills and the development of analytic thought process neglects the development of important non-verbal abilities.” This in turn, means that we are neglecting the development of the left-handers, as left-handedness is associated with the right brain, which is lateralised to perform functions of non-verbal abilities.
Despite facing difficulties, left and right-handers’ “fundamental differences in brain organisation” imply that conversions are not easily achieved. Besides that, being a left-hander does have its advantages, especially in sports. Substantiating this point is Marian Annette from the University of Leicester who thinks “right-handedness has been achieved at a reduction in the efficiency of the right hemisphere. Left-handers who do not have a weakened right hemisphere do better at a wide range of tasks, with the exception of early development of language.”

CHILD DEVELOPMENT AND LATERALISATION
Researches are continuing to shed light on the effects of lateralisation in child development today. As mentioned above with regards to the reasons for left-handers to remain as left-handers, children should be allowed to continue to use their dominant hands without interference. Besides, there have been increasing revelations on the visuospatial and musical abilities of the right hemisphere.
More importantly, as iterated by Clare Cherry et al in their book on Whole Child Development, “We develop not only the left or the right hemisphere but the whole brain, which must be a partner to itself; we develop the whole person”

CONCLUSION
The studies of lateralisation and human development cannot be fully explored given the length of this paper. Researches are continuously carried out to try and understand the workings of the human brain and functions of each hemisphere in human development. What is certain is that the right hemisphere can and will no longer be neglected as we begin to take into account its contributions in shaping the human race. “We do not have two brains, and we do not have half a brain. Rather, we have a two-sided brain that functions most productively when both sides are able to develop their partnership and work in unison, each complementing the other, and each having valuable contributions to make.”




REFERENCES
Cherry, Clare and Godwin, Douglas and Staples, Jesse. “Is the Left Brain Always Right?”. Australia: Hawker Brownlow. 1989

Corballis, Michael. “Human Laterality”. New York: Academic Press. 1983

Ornstein, Robert. “The Right Mind”. New York: Harcourt Brace & Company. 1997
Springer, Sally P. and Deutsch, Georg. “Left Brain, Right Brain”. New York: W.H. Freedom and Company. 1993

Wilson, Frank R. “The Hand”. New York: Pantheon Books. 1998