Functional load and frequency predict consonant emergence across five languages

Frequency can often predict when children will acquire units of language such as words or phones. An additional predictor of speech development may be a phone’s functional load (FL), or the contrastive work that a sound performs in a language. A higher FL may correlate with earlier phone emergence in child speech as children selectively converge upon highly meaningful contrasts in their input. This hypothesis is tested across five typologically-diverse languages that vary by phone inventory size and structure as well as word composition. Consonant FL was calculated over more than 390,000 words of child-directed speech. Results demonstrate that FL correlates positively with earlier consonant emergence in all languages. Models fit to bootstrapped corpus data include both FL and frequency as predictors, but suggest that frequency may be the stronger of the two. A need to complicate assumptions on the relationship between environmental effects and phonological development is discussed