Development of the use of word order in comprehension.

Thirty-three children aged between 19 and 38 months were presented with six reversible active and six reversible passive sentences and were required to act them out. For each child, mean length of utterance was calculated from a sample of spontaneous speech. Mean length of utterance was a more consistent predictor of performance than chronological age. Seven children with a mean length of utterance between 1.0 and 1.5 morphemes per utterance were unable to use the word order information in either type of sentence for comprehension. More developed children could comprehend reversible active sentences but not reversible passives. Children with a mean length of utterance between 3.0 and 3.5 morphemes per utterance systematically reversed the meaning of the reversible passives. The results are discussed in relation to previous studies of word order comprehension and studies of word order in production.