Verbal evolution: The more you say a word, the less likely it will change

As languages evolve, they tend to lose irregular forms of words. Oddball past tenses of irregular verbs morph into the regular form. In English, that means forming the past tense by appending "ed" to the root word as in "finish/finished." Linguists suspect that the more frequently an irregular form is used within a language community, the more resistant it is to such evolutionary change.

Two research teams, working independently, have used extensive statistical analysis to show that resistance to change does indeed correlate with the frequency of a word's usage. In fact, this seems to be a general rule governing the evolution of language.

You can see this rule at work in English today. "Forecast" is an irregular verb whose present and past tenses are the same – "forecast/forecast." It's used less frequently in spoken and written English than a high-usage irregular verb such as "say/said." But listen carefully to TV meteorologists and you'll hear some of them talking about what was "forecasted" yesterday. "Forecasted" is even showing up in some scientific papers. "Say/said" is here to stay. But "forecast/ forecast" is morphing into "forecast/forecasted."

Mathematician Erez Lieberman at Harvard University in Cambridge, Mass., and colleagues have studied the emergence of this rule in English over the past 1,200 years. They explained last month in Nature how they have tracked inflectional changes to 177 irregular verbs in Old-English (Beowulf's English) through Middle English (Chaucer's English) to Modern English.

By Chaucer's time, 145 of those old irregular forms remained and 98 of them are still with us today. (English speakers today might enjoy knowing that they are using some of the same irregular verbs that Beowulf and Chaucer spoke.)

Yet the rule that less-used irregular forms evolve into regular forms faster than much-used forms stands out in their analysis. They conclude that a "word that is 100 times less frequent regularizes 10 times as fast" as high-usage forms.

Judging from its usage frequency, the team speculates that "wed/wed" morphing into "wed/wedded" will likely be the next irregular verb to regularize. But judging from local TV weather reports "forecast/forecast" morphing into "forecast/forecasted" is getting there first. Our office dictionary already lists "wedded" and "forecasted" as alternatives in the conjugation of their respective verbs.

In the same issue of Nature, Mark Pagel, Quentin Atkinson, and Andrew Meade at the University of Reading in England explain how they made a comparable analysis using extensive English, Greek, Spanish, and Russian resources together with a comparative database of 200 fundamental vocabulary meanings in 87 Indo-European languages. They say it shows "that the frequency with which these words are used in modern language predicts their rate of replacement" over the past 6,000 to 10,000 years of Indo-European language evolution.

The researchers conclude that this relationship "accounts for approximately 50 percent of the variation in historical rates of lexical replacement." They then propose "that the frequency with which specific words are used in everyday language exerts a general and law-like influence on their rates of evolution."

Given the many environmental, psychological, and social influences on language, the Reading researchers find it "striking that word-use frequency alone can explain such a large portion of the historical variation in the rates of evolution" of our languages.