Lefthandedness

Left-handedness is the consistent preference for using the left hand for tasks such as writing, throwing, or tool use. It is one aspect of handedness, a broader motor bias that also involves other preferences. In most populations about 10% are left-handed, with regional variation typically from 7% to 12%.

Handedness emerges in early childhood and stabilizes with age, arising from genetic and environmental influences. No single gene explains it; heritability is modest (roughly 15–25%), with many genes of small effect and non-genetic factors. Brain lateralization also differs: while most right-handers have left-hemisphere language areas, left-handers show more variability, including right-hemisphere or bilateral language organization, which is not in itself a sign of impairment.

Historically some societies stigmatized left-handedness; today most cultures are more accommodating. Tools and layouts were often designed for right-handed users, leading to adaptations and ambidextrous strategies.

Left-handedness is not a disease and is not inherently linked to poor health. Some studies report associations with certain neurodevelopmental conditions, but these are correlations with small effects.

In sports and other interactive activities, left-handed individuals can have an advantage due to opponent unfamiliarity, evident in fencing, baseball, and boxing. But success depends on training and other factors.

Evolutionarily, left-handedness persists in populations, potentially due to frequency-dependent selection, with advantages when rare and a balance across the population.

In design and education, awareness of left-handedness promotes ambidextrous tools and inclusive approaches.