Mean Length of Utterance: A study of early language development in four Southern Bantu languages

Heather Brookes*, Patricia Makaure, Sefela Yalala, Hannah Danvers, Martin Mössmer, Francesca Little, Mikateko Ndhambi, Frenette Southwood, Babalwa Ludidi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Mean Length of Utterance (MLU) has been widely used to measure children's early language development in a variety of languages. This study investigates the utility of MLU to measure language development in four agglutinative and morphologically complex Southern Bantu languages. Using a variant of MLU, MLU3, based on the three longest sentences children produced, we analysed the utterances of 448 toddlers (16-32 months) collected using the MacArthur-Bates Communicative Development Inventory, a parent-report tool. MLU3, measured in words (MLU3-w) and morphemes (MLU3-m), significantly correlated with age and other indices of language growth (e.g., grammar and vocabulary). MLU3 measures also accounted for significant variance in language development particular morphosyntactic development. Our results suggest that MLU3-m is a more sensitive measure than MLU3-w. We conclude that MLU measured in morphemes provides a useful addition to other indices of language development in these kinds of morphologically complex languages.

Original languageEnglish
Article number00685
JournalJournal of Child Language
Publication statusPublished - 2024


  • Mean length of utterance
  • Southern Bantu languages
  • child language development


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