Correlation Does Not Imply Compensation: Complexity and Irregularity in the Lexicon

TL;DR

This study investigates the complex relationships between morphological irregularity, phonotactic complexity, word length, and frequency across multiple languages, revealing nuanced and sometimes contradictory patterns that challenge prior assumptions.

Contribution

It provides a comprehensive analysis of these relationships across 25 languages using advanced information-theoretic measures, highlighting variability and robustness issues in previous findings.

Findings

Positive relationship between irregularity and complexity within languages

Weak negative relationship between word length and irregularity

Some previous correlations are less robust than previously claimed

Abstract

It has been claimed that within a language, morphologically irregular words are more likely to be phonotactically simple and morphologically regular words are more likely to be phonotactically complex. This inverse correlation has been demonstrated in English for a small sample of words, but has yet to be shown for a larger sample of languages. Furthermore, frequency and word length are known to influence both phonotactic complexity and morphological irregularity, and they may be confounding factors in this relationship. Therefore, we examine the relationships between all pairs of these four variables both to assess the robustness of previous findings using improved methodology and as a step towards understanding the underlying causal relationship. Using information-theoretic measures of phonotactic complexity and morphological irregularity (Pimentel et al., 2020; Wu et al., 2019) on 25 languages from UniMorph, we find that there is evidence of a positive relationship between morphological irregularity and phonotactic complexity within languages on average, although the direction varies within individual languages. We also find weak evidence of a negative relationship between word length and morphological irregularity that had not been previously identified, and that some existing findings about the relationships between these four variables are not as robust as previously thought.