# The Forbidden Left Hand

Left-handedness looked like it tripled over the twentieth century. The simple explanation would be that people simply grew more willing, later on, to admit which hand they actually used. But old film footage, where nobody answers any question, shows the same low around 1900. School pressure on left-handed children may account for part of the later recovery; the studies do not establish a single cause.

## The low point sat around 1900

In 1986, National Geographic magazine collected responses from 1,177,507 Americans aged 10 to 86 about which hand they wrote and threw with. Researchers Avery Gilbert and Charles Wysocki sorted the answers by birth year: 3–4% of those born before 1920 were left-handed, against 11–12% of those born after 1950, three times as many, in the same country, answering the same question.

A giant survey can hide a slip of memory or social embarrassment. That is why the second result matters, obtained without asking anyone anything: I.C. McManus and Alex Hartigan recoded, frame by frame, 391 English people filmed between 1897 and 1913 by the Mitchell and Kenyon film operators, counting which hand each person waved at the camera with. Within the same footage, older people used their left hand more often than younger ones, the signature of a low point right around 1900, measured without relying on participants' reports.

Genetics alone cannot explain a shift this fast, from one generation to the next. A 2022 meta-analysis of 21,127 twin pairs finds that genetic inheritance accounts for at most a quarter of the differences in handedness between people; the rest is left open to factors other than genes, the only kind that could have changed between grandparents and grandchildren without a single mutation.

One documented change between grandparents born before 1920 and grandchildren born after 1950 was the weakening of school discipline: left-handed children were less often made to write with their right hand. That may account for part of the shift; the cited studies do not establish how much or rule out other causes.

## The correction targeted one gesture: writing

In many European schools, left-handed children could throw a ball, sweep a floor, or use scissors with whichever hand came naturally. A West German pedagogical guideline from 1960 left the choice of hand free for drawing and throwing, but specified that writing remained an activity specially reserved for the right hand. In Ireland, Britain, and the United States the practice was the same, even without one text that summed it up: teachers insisted, sometimes with punishment, until the child wrote with their right hand.

Neuroscience found the trace of that correction decades later. Hartwig Siebner used positron emission tomography to scan adults who had been left-handed at age six and were forced by their school to write with their right hand: while writing, their brains still activated regions in the right hemisphere, the ones that would have driven the left hand, as if suppressing a gesture the body had never forgotten. Stefan Klöppel found a similar trace in the physical structure of these "converted" left-handers' cortex. The effect appeared in anatomy shaped by years of correction, alongside the activation observed in Siebner's study.

The visible trace of that correction was simpler than a brain scanner: the ink stain under the heel of the palm, where a left hand drags across the line it just wrote, left to right, blotting its own ink before it dries. The Latin alphabet was never drawn for it.

## Ten gestures, one number

The questionnaire below is the instrument handedness research has used for over five decades: ten everyday gestures, one answer for each. It is not a diagnosis. It is a measurement you can repeat any time, and compare honestly against the numbers above.

1. Writing
2. Drawing
3. Throwing a ball, no target
4. Scissors
5. Toothbrush
6. Knife, without a fork
7. Spoon
8. Broom, the guiding hand
9. Striking a match
10. A jar lid, the hand that unscrews

LQ is your score on this test's own scale: −100 means you answered "always left" on all ten gestures, +100 means "always right." It is calculated by subtracting your left-hand answers from your right-hand answers, dividing by the total number of answers, and multiplying by 100, Oldfield's (1971) formula. Band thresholds follow Veale (2014); other studies draw the lines differently.

## Two fixed poles, with a gap between them

Neither historical source gives a year-by-year reading: the 1986 survey groups respondents by birth decade, and the Mitchell and Kenyon footage only covers 1897–1913. So this page shows two firm poles, before 1920 and after 1950, with a gap between them.

The "right-handed," "mixed," and "left-handed" thresholds above come from one convention (Veale, 2014); other studies draw the lines differently, so your exact LQ matters more than the label attached to it.

The genetic study reports writing-hand categories, while this test calculates LQ from ten gestures. Read the two classifications separately.

## A question to carry forward

How much of the observed increase reflects reduced social pressure, and how much reflects a real change in the prevalence of left-handedness?

## Sources

Every figure on this page comes from a citable source, verified directly or through at least two independent citations when the primary text was inaccessible.

- [Human handedness: A meta-analysis](https://doi.org/10.1037/bul0000229) · Psychological Bulletin, 146(6), 481–524 (2020). 200 studies, 2,396,170 people.
- [Hand preference and age in the United States](https://pubmed.ncbi.nlm.nih.gov/1528408/) · Neuropsychologia, 30(7), 601–608 (1992). 1,177,507 respondents, 1986 National Geographic survey.
- [The decline of left-handedness in Victorian England: arm-waving in the films of Mitchell and Kenyon](https://www.cell.com/current-biology/fulltext/S0960-9822(07)01686-7) · Current Biology, 17(18), R793–R794 (2007). 391 English subjects filmed 1897–1913.
- [Long-term consequences of switching handedness: a PET study on handwriting in 'converted' left-handers](https://www.jneurosci.org/content/22/7/2816) · Journal of Neuroscience, 22(7), 2816–2825 (2002).
- [Nurture versus nature: long-term impact of forced right-handedness on structure of pericentral cortex and basal ganglia](https://www.jneurosci.org/content/30/9/3271) · Journal of Neuroscience, 30(9), 3271–3275 (2010).
- [The assessment and analysis of handedness: The Edinburgh Inventory](https://doi.org/10.1016/0028-3932(71)90067-4) · Neuropsychologia, 9(1), 97–113 (1971).
- [Edinburgh Handedness Inventory – Short Form: a revised version based on confirmatory factor analysis](https://doi.org/10.1080/1357650X.2013.783045) · Laterality, 19(2), 164–177 (2014).
- [Genome-wide association study identifies 48 common genetic variants associated with handedness](https://doi.org/10.1038/s41562-020-00956-y) · Nature Human Behaviour, 5, 59–70 (2021). Published online 28 September 2020. 1,766,671 people.
- [Handedness in twins: meta-analyses](https://doi.org/10.1186/s40359-022-00723-z) · BMC Psychology, 10, article 11 (2022). 21,127 twin pairs and 54,270 people.

Marius Comper · https://mariuscomper.uk/mana-stanga-interzisa/en/