I have heard and read several times that one of the forces that drive language change is the so called "principle of least effort". According to this account, several changes are caused by an economy in pronunciation. Take this Wikipedia explanation, for example:

Speakers especially use economy in their articulation, which tends to result in phonetic reduction of speech forms. See vowel reduction, cluster reduction, lenition, and elision. After some time a change may become widely accepted (it becomes a regular sound change) and may end up treated as a standard. For instance: going to [ˈɡoʊ.ɪntʊ] → gonna [ˈɡʌnə], with examples of both vowel reduction [ʊ] → [ə] and elision [nt] → [n], [oʊ.ɪ] → [ʌ].

Is this a scientifically valid assertion? If so, how do you measure the cost (and thus the economy) of the pronunciation of a certain sound in a language?

2 Answers 2


Words with higher frequency can remain stable with higher variability in their pronunciation than words of lower frequency, because their occurrence is predictable and their recognition is not seriously hampered by variable pronunciation. Words with higher variability are more likely to significantly change in the course of language use.

Introducing frequency into the picture predicts that some words are more likely to change than others, but doesn't explain the trend towards simplicity of production. If the notion of simplicity of production is going to be useful, it will have to take on a somewhat narrow sense: reduced forms of words are not easier to produce, but they are simpler to produce. In other words, a highly skilled speaker of a language can use their knowledge about which variations are used in the speech community and their ability to pronounce words of the language with high precision to produce a word in a simpler, but still highly-controlled way. It is, after all, easier for second-language learners to produce non-reduced forms accurately than reduced forms. The idea seems reasonable, but I don't know of any laboratory studies purporting to measure simplicity of production, although there is a good chance they would have escaped my attention.



You might want to look into Robert Kirchner's "Lazy" (1997: 104) constraints in optimality theory, which posit that surface forms which require more "articulatory effort" are more marked. This accounts for processes such as postvocalic lenition of Spanish voiced stops (e.g. /lobo/ 'wolf' becomes [loβo]). In this example, the rationale that [β] requires less articulatory effort than [b] is simply that it requires less facial motion, and therefore less muscular exertion and energy expenditure, to close one's lips partially (forming the fricative) than to close them completely (forming the stop).

If I recall correctly, Kirchner assigns scores to different phones according to how much effort they require to produce, and his constraints take these scores into account. This might help answer your question about how to measure the cost of sound-production.

Kirchner, Robert (1997). Contrastiveness and faithfulness. Phonology, 14, 83–111.

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