Phonotactic Complexity and Its Trade-offs

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We present methods for calculating a measure of phonotactic complexity—bits per phoneme—that permits a straightforward cross-linguistic comparison. When given a word, represented as a sequence of phonemic segments such as symbols in the international phonetic alphabet, and a statistical model trained on a sample of word types from the language, we can approximately measure bits per phoneme using the negative log-probability of that word under the model. This simple measure allows us to compare the entropy across languages, giving insight into how complex a language's phonotactics is. Using a collection of 1016 basic concept words across 106 languages, we demonstrate a very strong negative correlation of − 0.74 between bits per phoneme and the average length of words.

@article{pimentel-etal-2020-phonotactic,
    author = {
        Tiago Pimentel and
        Brian Roark and
        Ryan Cotterell
    },
    article = {Transactions of the Association for Computational Linguistics (TACL)},
    title = {Phonotactic Complexity and Its Trade-offs},
    year = {2020},
    doi = {10.1162/tacl_a_00296},
    url = {https://aclanthology.org/2020.tacl-1.1/},
    pages = {1--18},
}