Another Year Passes: Happy Left Handers Day


International Left Handers Day was August 13th, the day when left handers cut the strings on bank pens, turn papers around on clipboards and staple papers on the opposite side to annoy the rest of you.  It was forty-five years ago, August 13, 1976, that Left Handers Day was founded.

(Yes, it was two weeks ago, but my job is eating my time.  The foreigner at the other school in my buxiban chain bailed in May when the mass spread happened.  He didn’t have the money to go two to three months without work, no speculation on his spending habits.  That means I’m covering and prepping the online classes for two schools, 30 different groups of kids per week until they hire a second teacher for October.  Not fun.  At least I’m getting paid.)

Dr. Marietta Papadatou-Pastou, Assistant Professor at the National and Kapodistrian University of Athens, was interviewed by the International Labour Organization for a podcast published on August 13, 2021:

Left-handed workers in a right-handed world

About 10 per cent of people are left handed, yet the world of work is overwhelmingly set up for right-handers. There are also numerous examples – historical and contemporary – of discrimination and stigma in relation to left-handed people.

International Left-handers Day, on August 13, aims to counter some of these disadvantages and draw attention to the strengths of the world’s left-handed workers and the problems they face.

Below the fold are a number of studies published over the last twelve months.  There were enough scientific publications this year that I didn’t have to write anything.  Good, I can dispense with the fluff pieces and “who’s a lefty?” lists.

September 2020 to the present has seen a lot of different research papers published on left handedness – or left pawedness, in one case.

September 2020: A paper in nature human behaviour shows a link between 48 genetic variants and handedness in a large scale study of 1.7 million people.  There are 41 for lefthandedness, and 7 for ambidexterity, and they are completely separate sets of variants.  A item from the University of Queensland expands on it further (and without a paywall, unlike the wall street journal):

Researchers get a better grip on left and right handedness

In the largest study of its kind to date, UQ researchers have identified 48 genetic variants that influence if a person is left-handed, right-handed or ambidextrous.

The research led by the University of Queensland and QIMR Berghofer Medical Research Institute also confirmed that environment plays a far larger part than genes in hand use preference.

UQ Diamantina Institute Professor David Evans said 41 of the identified genetic variants influenced a person’s chances of being left-handed. Seven were associated with ambidexterity, which describes when a person is equally proficient with each hand.

“The 41 genetic variants influencing left-handedness were different to the seven we identified for ambidexterity, and we saw very little correlation between the results for the two traits,” Professor Evans said.

“Although there is an enduring fascination with why some people are left or right-handed or both, understanding why some people are left-handed and others right-handed is also an important research question because handedness can influence brain structure and the way different functions are located within the brain.”

Studies of handedness in humans has shown that being XY and being LGBTQIA makes one more likely to be left handed.  As it turns out, the same applies to dogs, though the disparity of handedness is much closer than in humans, likely because we have digits for fine motor control.

Findings from the Largest Study on Left-Handedness in Dogs

About 10.6% of humans are left-handed (Papadatou-Pastou et al., 2020). While scientific research has shown that many animal species also show left- or right-handedness, the exact numbers are often not known due to small study sample sizes. A new study, published in the journal Applied Animal Behaviour Science, was aimed at determining how many dogs are left-handed and how many dogs are right-handed (Laverack et al., 2021)

[. . .]

To determine whether a dog was left-handed (or rather left-pawed) or right-handed, the researchers analyzed data from a so-called food retrieval task. In this task, owners were asked to obtain a plastic or cardboard tube that was wide enough so their dog could reach its paw into the tube. The owners were then instructed to place a treat near the end of the tube, so the dog had to reach into the tube with its paw to reach the treat. In total, this procedure was done three times. While most researchers would conduct more test trials than just three in a laboratory experiment, this low number might be due to the fact that also several other tests were performed in this survey.

[. . .]

Overall, about 74% out of the 17,901 tested dogs showed a clear paw preference, while the remaining 26% were classified by their owners as using both paws equally in the food retrieval task. Of the dogs that showed a clear preference for one paw over the other, 58.3% were right-handed. This number reached statistical significance, showing that most dogs are right-handed. It is interesting to note that 41.7% of the dogs that showed a paw preference were left-handed. Thus, left-handedness is much more common in dogs than in humans.

Interestingly, gender also affects handedness in dogs. Of female dogs, 60.7% were right-handed and 39.3% left-handed. In male dogs, left-handedness was more common: 56.1% were right-handed and 43.9% left-handed. This mirrors findings in humans that also show that men are more likely to be left-handed. (Learn more here.) Moreover, the researchers found that age affected handedness in dogs: Right-handedness was more common in older dogs than younger dogs, but this effect was specific for male dogs.

A study published in Nature (June 2021) shows that left handed people are much better at spatial awareness and visualization.

Handedness effects on motor imagery during kinesthetic and visual-motor conditions

Abstract

Recent studies show that during a simple movement imagery task, the power of sensorimotor rhythms differs according to handedness. However, the effects of motor imagery perspectives on these differences have not been investigated yet. Our study aimed to check how handedness impacts the activity of alpha (8–13 Hz) and beta (15–30 Hz) oscillations during creating a kinesthetic (KMI) or visual-motor (VMI) representation of movement. Forty subjects (20 right-handed and 20 left-handed) who participated in the experiment were tasked with imagining sequential finger movement from a visual or kinesthetic perspective. Both the electroencephalographic (EEG) activity and behavioral correctness of the imagery task performance were measured. After the registration, we used independent component analysis (ICA) on EEG data to localize visual- and motor-related EEG sources of activity shared by both motor imagery conditions. Significant differences were obtained in the visual cortex (the occipital ICs cluster) and the right motor-related area (right parietal ICs cluster). In comparison to right-handers who, regardless of the task, demonstrated the same pattern in the visual area, left-handers obtained higher power in the alpha waves in the VMI task and better performance in this condition. On the other hand, only the right-handed showed different patterns in the alpha waves in the right motor cortex during the KMI condition. The results indicate that left-handers imagine movement differently than right-handers, focusing on visual experience. This provides new empirical evidence on the influence of movement preferences on imagery processes and has possible future implications for research in the area of neurorehabilitation and motor imagery-based brain–computer interfaces (MI-BCIs).

[. . .]

Discussion

The results of the performed statistical analyses confirmed some of the research hypotheses. Indeed, the handedness significantly impacts the performance of imagery tasks. Similarly to the case study by Carino-Escobar et al.18, the left-handed achieved higher accuracy than the right-handed. However, the group differences of the KMI and VMI conditions matched the hypotheses only in the left-handers’ case. In this group, as expected, the VMI task was performed significantly better than KMI and on a higher level than by the right-handed. At the same time, the opposite effect was not found in the second group, where there were no significant differences in correctness between the KMI and VMI conditions. Therefore, we cannot confirm that the right-handed prefer a kinesthetic perspective in motor imagery, and this is the reason for better control, e.g. in MI-BCIs19.

[. . .]

Conclusions

Our studies’ results may provide new explanations of the different effects of the research on the relationship between handedness and MI-BCIs control18,19. According to our hypotheses, right-and left-handed differ in their ability to imagine a movement from a kinesthetic and visual-motor perspective. We have obtained partial confirmation of these assumptions at the behavioural and electroencephalographic levels. However, contrary to expectations, left-handers have achieved better results in the MI task, regardless of the experimental condition. It may result from the life experience of this group, who is forced to change their perspective more frequently in order to be able to use the tools designed with the right-handed. Another possible explanation is the reported differences in neuroanatomy45 and connections between cerebral structures16. However, due to limitations in our research procedure, this issue should be addressed in future studies.

This is a similar study by different authors, stating the left handers’ brains aren’t simply reversed from right handed peoples’, but are instead wired differently across the brain:

Left handers are less lateralized than right handers for both left and right hemispheric functions

Many neuroscientific techniques have revealed that more left- than right-handers will have unusual cerebral asymmetries for language. After the original emphasis on frequency in the aphasia and epilepsy literatures, most neuropsychology and neuroimaging efforts rely on measures of central tendency to compare these two handedness groups on any given measure of asymmetry. The inevitable reduction in mean asymmetry in the left-handed group is often postulated as being due to reversed asymmetry in a small subset of them, but it could also be due to a reduced asymmetry in many of the left-handers. These two possibilities have hugely different theoretical interpretations. Using fMRI localiser paradigms, we matched left- and right-handers for hemispheric dominance across four functions (verbal fluency, face perception, body perception, scene perception). We then compared the degree of dominance between the two handedness groups for each of these four measures, conducting t-tests on the mean laterality indices. The results demonstrate that left-handers with typical cerebral asymmetries are less lateralized for language, faces and bodies than their right-handed counterparts. These results are difficult to reconcile with current theories of language asymmetry or of handedness.

And another separate related study, showing a difference in the lateralization of the brain between left and right handed people.

In March 2021, the Institute of Labour Economics (Germany) published a paper on Left-Handedness and Economic Development, discussing how secularism led to a reduction of coercive forced hand switching and a rise in the percentage of people who are left handed, but also the economic disparity due to equipment being designed solely for right handed people.  Unfortunately, the paper doesn’t discuss the disparity in education, how schools do not teach left hand specific writing skills, which affects ability, performance, test scores and enjoyment of school.

This item from Psychology and Education covers that last part (full PDF of the article available on the link), advocating for left hand specific training for children:

“PSYCHOLOGICAL ASPECTS OF LEFT-HANDEDNESS: CONCEPT, CAUSES, AND PECULIARITIES”

A characteristic feature of left-handers is the insufficient and specific development of visual perception, which normally creates the basis for mastering reading and writing. Unfortunately children with left handedness do not receive adequate assistance in school, since education and upbringing are focused on right handed people. It is also shown that «traditional» retraining in early childhood can lead to distress, which has a negative impact on the children. Therefore, it is necessary to include in the educational process special methods and techniques. Thus it will be a favorable condition for their harmonious personal and intellectual development and effective mastering of various modules of the school curriculum. This article presents a theoretical model analysis of the causes and consequences of the development of sinistrality, briefly considered the psychological characteristics of left-handed children.

 

Comments

  1. Jazzlet says

    That means I’m covering and prepping the online classes for two schools, 30 different groups of kids per week until they hire a second teacher for October.

    That’s a lot of work, hope you manage to get some recreation in as well.

    .
    I don’t find it surprising that there is a genetic component to handedness, but I wonder if there would be a higher proportion of left-handers if our tool use had developed differently. It would be interesting to see work on our closer relatives, as well as looking at any evidence to be gained from archeaological tool finds. I imagine you could work out which hand a hand axe was used with for instance.

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