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An update on handedness and the preferred direction for turning(BIOMCH Archive 021282)

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  • An update on handedness and the preferred direction for turning(BIOMCH Archive 021282)

    It seems that handedness and chirality and direction of turning might
    all be inter-related. Professor David Morgan (of Biomedical Engineering,
    Monash University) told me that; "My understanding is that driving on
    the left in Europe is due to Napoleon, on purely ideological grounds,
    i.e. with liberty and fraternity ruling the land, having your sword
    available is not needed. Similar to the scouts left handshake" (i.e. I
    trust you to not draw your sword!)

    Bruce Etnyre (Kinesiology Department, Rice University) has found the
    BIOMCH-L archive reference for the responses to the first BIOMCH-L
    discussion about turning left and right: it is reference number 17883
    (he found it by doing a search for "left turn"). It was mainly about
    counter-clockwise running tracks but also included some discussion about
    how many things in general, naturally turn to the left or

    Chris Barr told me this interesting anecdote that might explain a few
    things: "My mum was left handed as a child, and is now right handed
    (although not quite of retirement age.) The reason she gives for this
    is that at school writing with you left hand was "wrong". When she was
    at school the teachers would actually tie her left hand behind her back
    or give her the cane on her left hand in order to make her write with
    her right hand. This type of incident was in no way isolated, and may
    account for the change in stats."

    On this topic Bruce Etnyre pointed out while the conventional assumption
    is that 10% of people are left-handed and 90% are right-handed, he has
    seen data that suggests that adolescents and pre-adolescents have about
    20% left-handed, late teens to 20's is about 15%, middle age is about
    10%, elderly is 5% and there are virtually no lefties over 80 y/o.

    Conrad Pearson (of siliconCOACH Ltd) raised the question of whether
    right handed people are always left footed. He provided the following
    "Handedness and longevity: archival study of cricketers" by John P
    Aggleton, J Martin Bland, Robert W Kentridge, Nicholas J Neave: this
    study tested whether handedness is associated with a change in
    longevity: their study looked at all first class cricketers born in the
    British Isles between 1840 and 1960 whose bowling hand was specified
    (right, n=5041; left, n=1132). A regression analysis of 5960 players
    showed no significant relation between mortality and handedness. Left
    handedness was, however, associated with an increased likelihood of
    death from unnatural causes and this effect was especially related to
    deaths during warfare.

    Siegfried Jaecques (of K.U. Leuven, Belgium) mentioned that he
    remembered reading about "a theory (maybe from a discussion on biomch-l)
    that the statistics on survival of left-handers vs right-handers were
    made with demographic data that spanned World War I and WWII. See
    Aggleton (1994. Indeed the left-handers had a higher probability of
    death in combat because weapon systems in those days were designed for
    right-handers. For example, the action of a standard rifle is very hard
    to operate with the left hand since the bolt handle is on the right. If
    you saw the movie "Saving private Ryan", you may remember that the
    sniper in the squad of Captain Miller is left-handed and there are a few
    scenes where you can see that his left sleeve gets stuck on the scope
    will cycling his gun. In the end, he gets shot by a German tank that he
    spotted too late because he was distracted."

    Bruce Etnyre made some similar remarks on this point: "Some explanations
    why left-handers don't live as long, on average, is that there are about
    50% more males than female left-handers. Males don't live as long, on
    average. Why? It goes to the nature and nurture question. Males
    participate in more risky behaviors than females, generally, so they get
    killed more often. Probably the most dangerous activity of daily living
    is driving a vehicle. Males, on average, drive more miles than females.
    Also, because left-handers live in a world primarily designed for
    right-handers, they are involved in more fatal accidents. For example,
    here are some things designed for right-handers which can be dangerous
    when used left-handed: firearms; gear shifts & gas/brake pedals (at
    least in countries driving on the right-hand side of the road); all
    power tools; and I'm sure there are others. Lefties are also frequently
    frustrated with other objects made for righties: watch stems;
    thermometers; musical instruments; cork screws, etc. etc. Also, infant
    and peri-natal mortality is greater for males (although their handedness
    has not been determined yet - generally that occurs at the developmental
    milestone of about 4-6 years). More males dying dying before age 1
    brings down the average considerably.

    Noel Lythgo (Royal Talbot Rehabilitation Centre, Melbourne) has told me
    that: "work involving small groups of no more than 20 able-bodied young
    and elderly adults (Sadeghi, Allard & Duhaime, 1997; Sadeghi, 2003;
    Sadeghi et al., 2003; Goble, Marino & Potvin, 2003, Sadeghi et al.,
    2004) suggests the behaviour of the limbs is symmetrical for outcome
    measures such as step length but asymmetrical for the lower limb moments
    that produce the step. This supports the idea of functional gait
    asymmetry, where one limb has a propulsive function and the other a
    supporting or stabilising function. This may lead to the tendency to
    circle when lost. Essentially, longer left steps are made due to the
    greater propulsion or push-off generated by the right limb (which
    carries the left limb further through the swing phase) coupled with
    shorter right steps made due to the lesser propulsion generated by the
    left limb (assuming right limb dominant)."

    Last but not least: according to a recent theory ("Hemispheric Asymmetry
    Reduction in Old Adults" or HAROLD) bi-hemispheric load-sharing might
    compensate for some aspects of age-related neuro-cognitive decline. You
    might have seen the recent article in "Time" magazine about "The
    Surprising Power of the Aging Brain": perhaps this "brain balancing"
    might also account for the ability of some "left-handers" to eventually
    learn to do tasks with their right hands (or become ambidextrous). Here
    is a little background information for anyone who is interested in doing
    further research on this topic. Positron emission tomography (PET) and
    functional magnetic resonance imaging (fMRI) can reveal how brain
    activity during cognitive performance changes as a function of aging
    (Cabeza, 2001). Studies using these techniques have led to the
    development of the new discipline of Cognitive Neuroscience of Aging.
    This article reviews functional neuro-imaging studies of cognitive aging
    in the domains of visual perception and memory functions. These studies
    have shown that brain activity tends to be less lateralized in older
    adults than in younger adults: this has led to a model of aging called
    Hemispheric Asymmetry Reduction in Old Adults (HAROLD). According to
    this theory bi-hemispheric load-sharing might compensate for some
    aspects of age-related neuro-cognitive decline. The HAROLD model
    integrates ideas and findings from psychology and neuroscience of aging
    (Cabeza, 2002). Indeed some older adults perform as well as young
    adults: recent studies of these high-performing older adults have shown
    that the high-performing seniors counteracted age-related neural decline
    through a reorganization of neuro-cognitive networks (Cabeza et al,
    2002). This might have something to do with the finding that many senior
    citizens achieve an increased balancing of the two halves of the upper
    brain as they age. Dolcos et al (2002) have reviewed the evidence for
    two models of aging and its relationship to hemispheric asymmetry: (a)
    the right hemi-aging model (a model that proposes that the right
    hemisphere shows greater age-related decline than the left
    hemisphere) and (b) the theory hemispheric asymmetry reduction in old
    adults (the "HAROLD model"): this model proposes that frontal activity
    during cognitive performance tends to be less lateralized in older than
    in younger adults. The authors concluded age-related asymmetry
    reductions might reflect functional compensation ("de-differentiation")
    and found that there is some slight evidence to support the compensation


    David McFarlane
    Ergonomist, WorkCover Authority
    New South Wales, Australia


    R. Cabeza, (2001), "Cognitive neuroscience of aging: contributions of
    functional neuroimaging", Scand J Psychol, Jul; 42(3): 277-86.

    R. Cabeza, (2002), "Hemispheric asymmetry reduction in older adults: the
    HAROLD model",
    Psychol Aging, Mar; 17(1): 85-100.

    R. Cabeza, N. Anderson, J. Locantore and A. McIntosh, (2002),
    Neuroimage, "Aging gracefully: compensatory brain activity in
    high-performing older adults",
    Nov; 17(3): 1394-402.

    F Dolcos, H. Rice and R. Cabeza, (2002), "Hemispheric asymmetry and
    aging: right hemisphere decline or asymmetry reduction", Neurosci
    Biobehav Rev. Nov; 26(7):819-25.

    J. Kluger, (2006), "The Surprising Power of the Aging Brain", Time,
    January 16, 84-87.

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