5973 History of hand preference

Objectives Hand dominance usually develops in children around 18 months old, while earlier hand preference may indicate cerebral palsy.¹ Hand preference in humans is thought to be related to the asymmetrical usage of human brains. For example, language is predominantly controlled by the left hemisphere, while creativity is largely dictated by the right hemisphere.² Right-handedness has predominated in humans throughout history. However in recent years, the percentage of left-handed children has risen, thought to be attributable to increased freedom in primary education.³ Methods Most primates do not display preference to use one hand over the other, suggesting that hand preference developed in humans since our evolutionary divergence, 5 to 7 million years ago.⁴ Ancient Mesopotamians considered left-handedness a form of divine punishment, while ancient Egyptians portrayed their enemies as left-handed as a mocking insult.⁵ In the Middle Ages, left-handed people were thought to be demon-possessed, or accused of witchcraft.⁶ This belief stemmed from ancient stories of Lucifer sitting at the left-hand of God before his exile from Heaven. Victorian England saw a steep decline in the proportion of left-handed children.³ Lower rates of left-handedness compared with today is thought to be predominantly due to children being encouraged to write with their right hand in school.⁷ Forced dextrality is linked to developmental issues; some children with forced right handed-ness may be misdiagnosed as having dyslexia or dyspraxia, due to their poor handwriting development and mal-coordination with their right hand, reported as early as the mid 1900's.⁸ Results In the present day, the proportion of left-handed children is rising, thought to be due to an increased allowance for children to learn to write with their preferred hand in school. However, around half of left-handed individuals still report being forced to use their right hand as a child.⁹ This remnant forced dextrality may be due to environmental factors placing unspoken pressure on children to become right-handed. In particular, the bias of educational equipment towards right-handed children, from right-handed scissors and pencil sharpeners, to the frustration of smudged ink across the page of a child trying to write with their left hand. Conclusion Children should be encouraged to develop their own hand preference, rather than forced by educational establishments or environmental factors to become right- handed. The stigma towards left-handedness has prevailed throughout history, and may encroach upon normal fine motor and language development skills. References Cerebral palsy in under 25s, NICE 2017. MC Corballis. Left brain, right brain: facts and fantasies 2014. IC McManus. The history and geography of human handedness 2009. KR Caspar, F Pallasdies, L Mader, H Sartorelli, S Begall. The evolution and biological correlates of hand preferences in anthropoid primates 2022. S Coren. Left-Handedness 1990. IC Manus, Right Hand, Left Hand 2002. WW Ireland. Notes on Left-Handedness 1880. TW Salmon. Reading, writing and speech problems in children 1938. E Vuoksimaa, M Koskenvuo, RJ Rose, J Kaprio. Origins of Handedness 2010.