Field of Science

Evolution of Irregular Verbs

I'm currently taking an amazing class offered by the Program for Evolutionary Dynamics (PED) at Harvard. The goal of the course (and the research program) is to study evolution---of animals, diseases, languages, and other entities---with full mathematical rigor. Today's class included a presentation by one of the PED researchers on the evolution of irregular verbs, based on an article that appeared in Nature in 2007.

Anyone who has ever studied a foreign language will remember with a sense of frustration that all the screwy irregular verbs were precisely the verbs like "to be" or "to go" that get used more often than any others. Obscure, rarely used verbs tend to conjugate in regular patterns.

These researchers found that early on in the English language, many verbs that are now regular, such as "help" or "walk", were once irregular ("I halp my friend study for his quiz yesterday.") As time went on, these verbs regularized (their conjugations evolved to the regular form) one by one, except for those very common verbs like "to be" and "to go" that remain highly irregular (how do you get "went" from "go"?)

Moreover, the speed at which these verbs regularized is directly related to the frequency of their usage. This relationship can be expressed in a remarkably simple mathematical law: the speed at which a verb regularizes is inversely proportional to the square root of its frequency. In other words, if verb A is used 100 times as much as verb B, verb B will regularize 10 times as fast.

The simplicity of this law suggests that there must be some kind of fundamental explanation---a simple model of language use that predicts this law mathematically. No such explanation has been found to date, but you can bet I'll be looking for one!


  1. None of the authors on that paper are linguists, I believe. While that does not say anything about this particular study, it is the kind of situation where an "outside perspective" can make things go horribly wrong.

  2. Ben, sounds like a great class, who's teaching it?

    Regarding the evolution of language, two important thrusts are the co-evolutionary theory of language and brain

    and Dan Everett's work:

    Keep us updated on the rest of the course!

  3. @blake--I think "horribly wrong" is something of an overstatement. Yes the paper was written by non-linguists, whose lack of expertise caused them to get some details wrong, but I don't think the critique invalidates the overall thrust of the research.

    @rafe--It's taught by Martin Nowak, a very smart guy. Thanks for the links!


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