A comparative study between mean length of utterance in morphemes (MLUm) and mean length of utterance in words (MLUw)

Prior to Brown's (1973) introduction of mean length of utterance in morphemes (MLUm), child language researchers and speech-language pathologists used mean length of utterance in words (MLUw) as a measurement of a child's gross language development. After Brown (1973) and others documented MLUm to be a measure which was correlated with the development of morphological and syntactic skills in young children, the practice of counting MLUm became more widely used and accepted. In the present study, MLUw and MLUm scores of 40 language transcripts from typically-developing, English-speaking children between the ages of 3;0 and 3;10 were compared. Results indicated that MLUm and MLUw are almost perfectly correlated. This finding suggests that MLUw can be used as effectively as MLUm as a measurement of a child's gross language development.