The emerging ability to comprehend language: an experimental approach.

A new methodology was introduced to study the emergence of language comprehension. 30 infants 9--17 months of age received naturalistic training on the name of a salient object in experiment 1 (e.g., live rabbit) and on the name of a simple action inexperiment 2 (e.g; pressing to activate a toy). In both experiments, infants were subsequently probed for recognition of the previously unfamiliar trained name, and responses were videotaped and scored for gaze, gesture, and vocalization. Comprehension was estimated for each individual on the basis of the infant's distribution of target, baseline, and false positive responses to target and control probes. Developmental change in the ability to comprehend trained names was analyzed across 3 age groups: 9--11 months, 12--14 months, and 15--17 months. Cross-sectional and longitudinal results from experiments 1 and 2 all demonstrate dramatic improvement in receptive language capacity over the age range studied. Discrepancies between the comprehension and production of trained names are discussed.