In typical development, what does an increasing MLU indicate?

In typical development, what does an increasing MLU indicate?

• A. Increasing vocabulary size only.
• B. Increasing phoneme inventory.
• C. Increasing syntactic complexity.
• D. Increasing narrative coherence only.

Answer: (C)

Mean length of utterance captures how syntactically complex a child’s speech is. As kids grow, they don’t just put more words together; they start using grammatical endings and function words, making each utterance longer and more morphologically rich. Since MLU is measured in morphemes per utterance, this increase tracks the child’s development of grammar and sentence structure, not just vocabulary size, phoneme inventory, or narrative coherence. For example, moving from “dog run” to “the dogs are running” adds articles, plurals, and tense/morpheme markers, boosting the MLU. That’s why increasing MLU best indicates increasing syntactic complexity.

Mean length of utterance captures how syntactically complex a child’s speech is. As kids grow, they don’t just put more words together; they start using grammatical endings and function words, making each utterance longer and more morphologically rich. Since MLU is measured in morphemes per utterance, this increase tracks the child’s development of grammar and sentence structure, not just vocabulary size, phoneme inventory, or narrative coherence. For example, moving from “dog run” to “the dogs are running” adds articles, plurals, and tense/morpheme markers, boosting the MLU. That’s why increasing MLU best indicates increasing syntactic complexity.