# The Ink Stain

Left-handedness looked like it tripled over the twentieth century. What actually eased off was the discipline that hid it: a survey of over a million Americans and street footage from England in 1900, using completely different methods, both land on the same historical low point, right around 1900.

## A historical low, not a modern rise

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## The correction targeted one gesture: writing

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## 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 = (right − left) / (right + left) × 100, Oldfield's (1971) formula. Band thresholds follow Veale (2014); other studies draw the lines differently.

## Two fixed points, not a smooth curve

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, not a smooth curve 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 of 1,766,671 people used for the population comparison is still a preprint, not yet published in a peer-reviewed journal as of this page.

## A question to carry forward

Next time someone says left-handedness "went up," ask them: did the number of left-handers rise, or did the number of corrected children fall?

## 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/10.1101/831321) · bioRxiv 831321 (2019), not yet peer-reviewed. 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/pata-de-cerneala/en/