Cold, arid environments, compared to warm, humid climates, negatively influence phonation in human tonal languages by restricting vocal cord movement and control, a study finds. Such languages, particularly those with complex tonality, primarily have developed in humid contexts. Previous studies on vocal fold physiology have shown hydration directly impacts pitch and amplitude; aridity worsens voice quality and may have long-term effects. Dehydrated vocal cords also are associated with increased phonation effort and threshold pressure. Caleb Everett and colleagues assessed global geographic language distribution via two phonological databases representing more than 3,700 languages, and discovered most of the over 600 languages with complex tone lie in the tropics. Their study focused on locales’ mean specific humidity and indicates complex tonality is more significantly influenced by humidity than temperature, even when controlled for genealogical factors. Complex tonal languages rarely appear in arid regions, whether hot or cold. This pattern holds within continents and major language families, and among language isolates. Findings suggest human sound systems are more ecologically adaptive than previously thought, according to the authors, who acknowledge additional research on the effects of ambient air on tone production and other sound patterns is needed.
Proceedings of the National Academy of Sciences (PNAS) article #1417413112: “Climate, vocal folds, and tonal languages: Connecting the physiological and geographic dots,” by Caleb Everett et al.
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This tip sheet was written for Lindsey Leake’s 491.750 Contemporary Science and Medical Writing: Creative and Professional Forms course at the Johns Hopkins University Krieger School of Arts and Sciences on Feb. 20, 2021.