High functional load inhibits phonological contrast loss: A corpus study

•Phoneme contrasts with high functional load are predicted to be resistant to loss.•This hypothesis is nearly a century old, but has been difficult to test.•Our novel strategy analyzing pooled data across languages supports the hypothesis.•Phoneme contrasts that distinguish more words are significantly resistant to loss.•These results contradict traditional models separating the lexicon from grammar.

For nearly a century, linguists have suggested that diachronic merger is less likely between phonemes with a high functional load – that is, phonemes that distinguish many words in the language in question. However, limitations in data and computational power have made assessing this hypothesis difficult. Here we present the first larger-scale study of the functional load hypothesis, using data from sound changes in a diverse set of languages. Our results support the functional load hypothesis: phoneme pairs undergoing merger distinguish significantly fewer minimal pairs in the lexicon than unmerged phoneme pairs. Furthermore, we show that higher phoneme probability is positively correlated with merger, but that this effect is stronger for phonemes that distinguish no minimal pairs. Finally, within our dataset we find that minimal pair count and phoneme probability better predict merger than change in system entropy at the lexical or phoneme level.