Extending a word’s meaning, whether by adult linguistic communities or by children, relies on the same cognitive foundation

Whether it’s a child extending their nonsense word for “duck” to encompass other birds, or broader adult linguistic communities dubbing a new piece of computer technology a “mouse” for its resemblance to the animal, humans are adept at extending word meanings. But do these two examples of the phenomenon of reusing the same word for multiple meanings really depend on the same process? A new study by Thomas Brochhagen and colleagues concludes after examining extensions in more than 1,400 languages that individual and population-level word meaning extension share a cognitive foundation. The foundation consists of knowledge about objects, events, properties and relations – such an object having a certain shape or an idea evoking a certain feeling – and using this knowledge to link a thing or idea that the person or population doesn’t yet have a word for to the current meaning of known words, based on similarities between the two. The computational framework developed by Brochhagen et al. used datasets of (1) common word overextensions used by children (individual-level) as they learn to speak, (2) documented historical (population-level) changes in a word’s meaning over time, and (3) a global database about colexification (i.e., when related meanings are expressed with the same word, like the same word “dit” used for “finger and toe”). The study will be helpful as linguists work to “develop a theory of language change and evolution that can link the micro processes operating within individuals over milliseconds, to those operating in communities over years, all the way up to the macro processes operating between communities over centuries,” writes Simon Greenhill in a related Perspective.