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Irregular Verbs – Fossils of Linguistic And Social Rules

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How ‘holp’ became ‘helped’

Studies link frequency of word use to how fast words evolve.

People talkingWhat did you say? Infrequently-used words have a habit of changing.Getty

The less often a word is said, the faster it will change over time, whereas more-often uttered words are resistant to change. In this week’s Nature, two groups publish analyses of this trend, which quantify it and compare it with biological evolution.

The idea that aspects of culture might ‘evolve’ in in a similar way as biological organisms dates back to Darwin himself. The notion was given a big push forwards in 1976, when Richard Dawkins introduced the concept of ‘memes’ — aspects of culture or fashion that “propagate themselves … by leaping from brain to brain”. That idea proved to be a successful meme in itself, becoming often-referenced in the literature. But, as Tecumseh Fitch, a psychologist at the University of St Andrews in Scotland, points out “not much has been done” to quantify the effect.

“There is this general idea that culture evolves, but it is more of a metaphor than something that has teeth — that obeys precise mathematical rules,” says Erez Lieberman, a specialist in evolutionary maths at Harvard University. “I wondered: can you make this metaphor be real? Can you show a process like natural selection that is affecting ideas or language?”

I getted it

Lieberman was struck by this idea when he learned that the ten most common verbs in English (be, have, do, go, say, can, will, see, take, get) are all irregular. Instead of their past tenses ending in ‘-ed’, as do 97% of English verbs, they take the peculiar forms of was, had, did, went, said, could, would, saw, took and got.

Researchers suppose that this is because often-used irregulars are easy to remember and get right. Seldom-used irregulars, on the other hand, are more likely to be forgotten, so speakers often mistakenly apply the ‘-ed’ rule. The most commonly used word that they found this happened to was the verb ‘to help’ – the past tense used to be ‘holp’, but is now ‘helped’.

This could be seen as analogous to the way that crucially needed genes tend to stay the same throughout biological evolution, whereas those for less-often-used or specialist traits have more freedom to evolve.

Lieberman wondered whether he could quantify the effect. He and his team looked at 177 verbs with varying frequencies of use that were irregular in Old English, and examined how many had been regularized into the ‘-ed’ past tense by the eras of Middle and Modern English. They found that an irregular verb used 100 times less frequently is regularized 10 times as fast. For the more mathematically inclined, this can be expressed as: ‘The half-life of irregular verbs is proportional to the square root of their frequency.

Translate this

At the same time, a different group led by evolutionary bio-informaticist Mark Pagel of the University of Reading, UK, looked at 200 basic words across different Indo-European languages, to estimate their rates of evolution.

Some words sound very similar, or can be traced back to a common origin by linguists, throughout many of the languages, which suggests these words were resistant to evolution. The English word ‘water’, for example, is similar to the now-extinct European Gothic word ‘wato’, along with words in many other modern European languages. Other words were markedly different across languages, suggesting they had evolved separately and more quickly (see Table 1).

When Pagel’s team plotted frequency of word use against rate of evolution for four languages (Greek, Spanish, English and Russian), they too found that less-frequently-used words evolved faster, and that frequency can explain half of the rate of evolution.2

“The easiest way to think about it is that changes to the higher-frequency words are less likely to be accepted,” says Pagel. “If I say there are two guys coming over the hill to kill us, and in fact there are 20, we might end up dead.”

The meaning of it all

Both papers were written by teams with evolutionary biology backgrounds, and both call attention to the similarities between language change and the evolution of species. Leiberman even refers to early English as a “primordial soup” of verb forms in his paper.

Brian Joseph, a historical linguist at Ohio State University in Columbus and the editor of the journal Language, says that’s going too far. Early English, he says, was “just as regular and rule-based” as modern language – it just had more complicated rules.

“The analogy with darwinian evolution is crude, although not useless,” says Stephen Pinker, a language and cognition specialist at Harvard. “Some portion of the variance can be accounted for by a quantitative variable such as frequency, but much more remains unexplained. You can’t understand language change without looking at the cognitive psychology of the human brains that learn and transmit the words.”

Nature 449, 713-716 (11 October 2007) | doi:10.1038/nature06137; Received 20 March 2007; Accepted 27 July 2007

Quantifying the evolutionary dynamics of language

Erez Lieberman1,2,3,5, Jean-Baptiste Michel1,4,5, Joe Jackson1, Tina Tang1 & Martin A. Nowak1

  1. Program for Evolutionary Dynamics, Department of Organismic and Evolutionary Biology, Department of Mathematics,
  2. Department of Applied Mathematics, Harvard University, Cambridge, Massachusetts 02138, USA
  3. Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  4. Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
  5. These authors contributed equally to this work

Correspondence to: Erez Lieberman1,2,3,5 Correspondence and requests for materials should be addressed to E.L. (Email:

Human language is based on grammatical rules1, 2, 3, 4. Cultural evolution allows these rules to change over time5. Rules compete with each other: as new rules rise to prominence, old ones die away. To quantify the dynamics of language evolution, we studied the regularization of English verbs over the past 1,200 years. Although an elaborate system of productive conjugations existed in English’s proto-Germanic ancestor, Modern English uses the dental suffix, ‘-ed’, to signify past tense6. Here we describe the emergence of this linguistic rule amidst the evolutionary decay of its exceptions, known to us as irregular verbs. We have generated a data set of verbs whose conjugations have been evolving for more than a millennium, tracking inflectional changes to 177 Old-English irregular verbs. Of these irregular verbs, 145 remained irregular in Middle English and 98 are still irregular today. We study how the rate of regularization depends on the frequency of word usage. The half-life of an irregular verb scales as the square root of its usage frequency: a verb that is 100 times less frequent regularizes 10 times as fast. Our study provides a quantitative analysis of the regularization process by which ancestral forms gradually yield to an emerging linguistic rule.



Nature 449, 717-720 (11 October 2007) | doi:10.1038/nature06176; Received 30 April 2007; Accepted 17 August 2007

Frequency of word-use predicts rates of lexical evolution throughout Indo-European history

Mark Pagel1,2, Quentin D. Atkinson1 & Andrew Meade1

  1. School of Biological Sciences, University of Reading, Whiteknights, Reading, Berkshire, RG6 6AS, UK
  2. Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501, USA

Correspondence to: Mark Pagel1,2 Correspondence and requests for materials should be addressed to M.P. (Email:

Greek speakers say “omicronupsilonrhoUnfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact“, Germans “schwanz” and the French “queue” to describe what English speakers call a ‘tail’, but all of these languages use a related form of ‘two’ to describe the number after one. Among more than 100 Indo-European languages and dialects, the words for some meanings (such as ‘tail’) evolve rapidly, being expressed across languages by dozens of unrelated words, while others evolve much more slowly—such as the number ‘two’, for which all Indo-European language speakers use the same related word-form1. No general linguistic mechanism has been advanced to explain this striking variation in rates of lexical replacement among meanings. Here we use four large and divergent language corpora (English2, Spanish3, Russian4 and Greek5) and a comparative database of 200 fundamental vocabulary meanings in 87 Indo-European languages6 to show that the frequency with which these words are used in modern language predicts their rate of replacement over thousands of years of Indo-European language evolution. Across all 200 meanings, frequently used words evolve at slower rates and infrequently used words evolve more rapidly. This relationship holds separately and identically across parts of speech for each of the four language corpora, and accounts for approximately 50% of the variation in historical rates of lexical replacement. We 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. Our findings are consistent with social models of word change that emphasize the role of selection, and suggest that owing to the ways that humans use language, some words will evolve slowly and others rapidly across all languages.


Written by huehueteotl

October 11, 2007 at 11:53 am

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