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Lateral thinking |
Current rating: 0 |
by LARRY
(No verified email address) |
07 Jun 2002
Modified: 08:05:11 AM |
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A handy guide shows that there's more to left and right than meets the eye. |
Right Hand, Left hand: The Origins of Asymmetry in Brains, Bodies, Atoms and Cultures
by Chris McManus
Weidenfeld & Nicolson: 2002. 256 pp. £20, $27.95
Taking sides: composites of the halves of Edgar Allan Poe's face (centre) highlight human asymmetry.
The causes and consequences associated with right- and left-handedness have been the focus of a growing body of research in the past 20 years. Indeed, laterality now even has its own journal: Laterality: Asymmetries of Body, Brain and Cognition, published by the Psychology Press. The scope and range of scientific disciplines now investigating laterality is the subject of this wonderful book by Chris McManus. Although its title implies that the focus is on handedness, don't be misled, for there is much more in this volume. The range of topics that it covers is far-reaching, and readers from a wide range of disciplines including physics, biology, chemistry, neuroscience and psychology will all find some aspects of the book intriguing from their own perspective.
Those who appreciate the history of science will not be disappointed either. McManus goes to great lengths to present a historical context for each of the topics discussed, and shows how the various disciplines are related and were often considered by our scientific founding fathers. He discusses topics ranging from asymmetry in the structure of amino acids to the socio-linguistic origins of the words 'left' and 'right'. He treats readers to a diverse set of observations, such as the fact that the skin of certain species of toad is extremely psychoactive because of differences in the distributions of left- and right-handed amino acids. And there is a wonderful discussion of the religious and political meanings of 'right' and 'left' in relation to the origins of such words as 'sinistrality' or the common reference to the left hand as the 'sinister' one.
McManus begins by describing a patient who exhibited situs inversus, a medical condition in which an individual has the organs reversed, with, for example, the heart on the right side instead of the left. The patient is right-handed, a point that serves as the juxtaposition for much of the book. Most people are right-handed and most people have their heart on the left side of the chest cavity. Therefore, because individuals with situs inversus have reversed organ asymmetries, one might assume that they would be left-handed. Modern research has shown that this assumption is wrong, but the example is revealing because it extends the concept of laterality beyond the traditional realm of handedness. The right-handed situs inversus patient represents the dual definition of laterality, defined first as a morphological phenomenon and secondly as a behavioural and functional process. Each form of laterality is autonomous from the other, but both are equally puzzling in terms of their origins.
From this basic premise, McManus begins by describing the historical and philosophical questions of why asymmetry exists. In particular he discusses the deeper question of right and left as absolute or relative degrees of space. Right and left are relative to the perspective of the viewer, so one need look no further than into a mirror to understand the fundamental problem.
In his discussion of the origins of human handedness, McManus presents a fair and representative review of various genetic, developmental and cultural models of handedness that have arisen over the years. He uses his own genetic model to explain individual variation in the expression of right- and left-handedness as well as variation between different cultures. Finally, he discusses several myths, misunderstandings and idiosyncrasies of left-handedness. For example, it is noted that a significantly higher proportion of left-handed individuals have been president of the United States compared with the population as a whole, and that left-handed individuals do not really have a shorter lifespan than right-handed individuals, as some believe.
This part of the book is a sometimes amusing, light-hearted addition to the otherwise empirically driven arguments in the preceding chapters, and many readers will find them both delightful and informative. I was disappointed that greater attention was not given to the plethora of recent findings on limb preferences in animals, including lower and higher vertebrates. Although some of these findings are referenced and briefly discussed, they are not fully presented — a shame in a book that purports to describe the origins of handedness. However, several recent books have been dedicated to the topic of behavioural laterality in animals, such as Comparative Vertebrate Lateralization (Cambridge University Press, 2002) edited by Lesley Rogers and Richard Andrews. Perhaps McManus opted not to include a lengthy discussion in his book to save space and to avoid distracting readers from the larger issues at hand.
Minor criticisms aside, he has done a marvellous job of summarizing and integrating a wide range of findings from various disciplines addressing questions on the nature of right and left. The presentation and clarity of the topics is palatable to both the scientific and lay communities, making this volume well worth reading.
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what the hell is this? |
by what the hell is this?
(No verified email address) |
Current rating: 0
07 Jun 2002
|
Larry, you need to pull that broom stick out of your ass !!
so you can write somthing worth reading !! |
