MLU
Mean Length of Utterance, a measure of grammatical development calculated as the average number of morphemes per utterance. MLU is a key indicator of developmental stage.
Real World
In Brown's longitudinal study, Eve reached an MLU of 4.0 at around 26 months while Adam reached the same MLU at 42 months — showing that MLU tracks grammatical maturity more accurately than chronological age alone.
Exam Focus
Define MLU precisely as morphemes per utterance (not words) to avoid a common mark-losing error in AO1 responses.
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