Age-relation, reliability and grammatical validity of measures of utterance length

ABSTRACT This study evaluated the age-relationship, intra-sample reliability and grammatical validity of MLU-like measures of utterance length in the free speech of 21 normally developing children aged 1;8 to 2;8 with MLU between 1·05 and 3·06. Contrary to a previous study by Klee & Fitzgerald (1985). it was found that measures of utterance length hold a good relation with age, are reliable and predict grammatical development well in the age and MLU range considered. It is argued that there are identifiable points in the developmental evolution of MLU and MLU-like indices beyond which their reliability and validity have serious problems. Below these points, they constitute sound measures of syntactic development.