What does MLU stand for and how is it calculated?

• A. Mean length of utterance; total morphemes divided by total utterances
• B. Morpheme length unit; total morphemes divided by total words
• C. Mean language usage; total words divided by number of utterances
• D. Multilevel utterance index; total morphemes per sentence

Answer: (A)

Mean length of utterance measures how many morphemes a child uses on average per spoken utterance, reflecting syntactic development. To calculate it, take a language sample from the child, count every morpheme in each utterance (including free morphemes like cat, run and bound morphemes like -s, -ed, -ing; each bound morpheme counts as one), sum all morphemes, and divide by the total number of utterances in the sample. For example, if there are 6 utterances with a total of 18 morphemes, the MLU is 3.0. This value tends to rise with age as children's syntax becomes more complex.