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Quantifying the evolutionary dynamics of language


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.

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Figure 1: Irregular verbs regularize at a rate that is inversely proportional to the square root of their usage frequency.
Figure 2: Irregular verbs decay exponentially over time.
Figure 3: Extrapolating forward and backward in time using the observation that regularization rate scales as the square root of frequency.

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  1. Chomsky, N. Aspects of the Theory of Syntax (MIT Press, Cambridge, 1965)

    Google Scholar 

  2. Lightfoot, D. The Development of Language: Acquisition, Change and Evolution (Blackwell, Oxford, 1999)

    Google Scholar 

  3. Clark, R. & Roberts, I. A computational model of language learnability and language change. Linguist. Inq. 24, 299–345 (1993)

    Google Scholar 

  4. Abrams, D. & Strogatz, S. Modelling the dynamics of language death. Nature 424, 900 (2003)

    Article  ADS  CAS  Google Scholar 

  5. Nowak, M. A., Komarova, N. L. & Niyogi, P. Computational and evolutionary aspects of language. Nature 417, 611–617 (2002)

    Article  ADS  CAS  Google Scholar 

  6. Hooper, J. in Current Progress in Historical Linguistics (ed. Christie, W.) 95–105 (North-Holland, Amsterdam, 1976)

    Google Scholar 

  7. Hauser, M. D., Chomsky, N. & Fitch, W. T. The faculty of language: what is it, who has it, and how did it evolve? Science 298, 1569–1579 (2002)

    Article  ADS  CAS  Google Scholar 

  8. Chomsky, N. & Lasnik, H. in Syntax: An International Handbook of Contemporary Research (ed. Jacobs, J.) 506–569 (de Gruyte, Berlin, 1993)

    Google Scholar 

  9. Dougherty, R. C. Natural Language Computing (Lawrence Erlbaum, Hillsdale, 1994)

    MATH  Google Scholar 

  10. Stabler, E. P. & Keenan, E. L. Structural similarity within and among languages. Theor. Comput. Sci. 293, 345–363 (2003)

    Article  MathSciNet  Google Scholar 

  11. Niyogi, P. The Computational Nature of Language Learning and Evolution (MIT Press, Cambridge, 2006)

    Book  Google Scholar 

  12. Labov, W. Transmission and diffusion. Language 83, 344–387 (2007)

    Article  Google Scholar 

  13. Pinker, S. Words and Rules: The Ingredients of Language (Basic Books, New York, 1999)

    Google Scholar 

  14. Kroch, A. Reflexes of grammar in patterns of language change. Lang. Var. Change 1, 199–244 (1989)

    Article  Google Scholar 

  15. Kroch, A. in Papers from the 30th Regional Meeting of the Chicago Linguistics Society: Parasession on Variation and Linguistic Theory (eds Beals, K. et al.) 180–201 (CLS, Chicago, 1994)

    Google Scholar 

  16. Pinker, S. The irregular verbs. Landfall 83–85 (Autumn issue, 2000)

    Google Scholar 

  17. Bybee, J. Morphology: a Study of Relation Between Meaning and Form (Benjamins, Amsterdam, 1985)

    Book  Google Scholar 

  18. Greenberg, J. in Current Trends in Linguistics III (eds Sebeok, T. A. et al.) 61–112 (Mouton, The Hague, 1966)

    Google Scholar 

  19. Bybee, J. From usage to grammar: the mind’s response to repetition. Language 82, 711–733 (2006)

    Article  Google Scholar 

  20. Corbett, G., Hippisley, A., Brown, D. & Marriott, P. in Frequency and the Emergence of Linguistic Structure (eds Bybee, J. & Hopper, P.) 201–226 (Benjamins, Amsterdam, 2001)

    Book  Google Scholar 

  21. Hare, M. & Elman, J. Learning and morphological change. Cognition 56, 61–98 (1995)

    Article  CAS  Google Scholar 

  22. Marcus, G., Brinkmann, U., Clahsen, H., Wiese, R. & Pinker, S. German inflection: the exception that proves the rule. Cognit. Psychol. 29, 189–256 (1995)

    Article  CAS  Google Scholar 

  23. Van der Wouden, T. in Papers from the 3rd International EURALEX Congress (eds Magay, T. & Zigány, J.) 363–373 (Akadémiai Kiadó, Budapest, 1988)

    Google Scholar 

  24. Zipf, G. K. Human Behavior and the Principle of Least Effort (Addison-Wesley, Cambridge, 1949)

    Google Scholar 

  25. Miller, G. A. Some effects of intermittent silence. Am. J. Psychol. 70, 311–314 (1957)

    Article  CAS  Google Scholar 

  26. Yang, C. Knowledge and Learning in Natural Language (Oxford Univ. Press, New York, 2002)

    Google Scholar 

  27. Glushko, M. Towards the quantitative approach to studying evolution of English verb paradigm. Proc. 19th Scand. Conf. Ling. 31, 30–45 (2003)

    Google Scholar 

  28. Kroch, A. & Taylor, A. Penn-Helsinki Parsed Corpus of Middle English [CD-ROM] 2nd edn. (2000) 〈

Download references


This work was supported by the John Templeton Foundation and by a grant from the NSF-NIH joint programme in mathematical biology. The Program for Evolutionary Dynamics is sponsored by J. Epstein. E.L. was supported by the National Defense Science and Engineering Graduate Fellowship and the National Science Foundation Graduate Fellowship. We thank S. Pinker, J. Rau, D. Donoghue and A. Presser for discussions, and J. Saragosti for help with visualization.

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Correspondence to Erez Lieberman.

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Supplementary information

Supplementary Information

This file contains the main Supplementary Information for the paper with Supplementary Tables 1-7 and Supplementary Figures S1-S2 with Legends. It includes a table of all the irregular verbs found, as well as their frequency and relevant source text. It also provides a description of the Irregular equation, and Supplementary Discussion of the dynamics within rules and of changes in frequency since Middle English with additional references. (PDF 2657 kb)

Supplementary Data

This file contains Supplementary Data which is a tab-delimited text file containing all of the source data. (TXT 5 kb)

Supplementary Zip File

This file is a zipped version of all the Python source code, enabling the reader to browse the code and reproduce the results using the Supplementary Data as the sole input. (ZIP 162 kb)

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Lieberman, E., Michel, JB., Jackson, J. et al. Quantifying the evolutionary dynamics of language. Nature 449, 713–716 (2007).

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