The relation between grammatical development and mean length of utterance in morphemes

ABSTRACT A widely held practice in many studies of child language development and disorders has been to employ an easily calculated numerical metric, mean length of utterance measured in morphemes (MLU), as a ‘general index of grammatical development’. While this practice seems to have found acceptance among many students of child language, the usefulness of MLU past Stage II has been assumed but never empirically tested. This study evaluated the grammatical performance and MLU of 18 normally developing 2- and 3-year-old children and found that MLU did not correlate significantly with age ( r = 0·26), nor did it discriminate children's profiles of grammatical development.