Acquisition of singular-plural morphology.

A manual search paradigm explored the development of English singular-plural comprehension. After being shown a box into which they could reach but not see, infants heard verbal descriptions about the contents of the box (e.g., "There are some cars in the box" vs. "There is a car in the box)" and were then allowed to reach into the box. At 24 months of age, but not at 20 months, infants' search patterns were influenced by verbal number markings. However, verbal number marking did not influence search behavior when plurality was signaled by noun morphology alone. These data converge with parental reports and preferential looking studies concerning the developmental course of mastery of English plural marking and show that infants can create a mental model of the number of objects on the basis of singular-plural morphology alone.