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Acquisition of English Number Marking: The Singular-Plural Distinction

We present data from a preferential looking method to investigate when infants have mapped singular and plural markers in English onto the semantic distinction between singleton sets and sets with more than 1 individual. Twenty- to 36-month-old children heard sentences that marked number in 1 of 2 ways: (a) redundantly with verb morphology, lexical quantifiers, and noun morphology ("Look, there ARE SOME blicketS"/"Look, there IS A blicket") or (b) only with noun morphology ("Look at the blicketS"/"Look at the blicket"). Twenty-four-month-old infants, but not 20-month-old infants, looked at the screen that matched the carrier sentence with respect to singular-plural distinction when number was expressed on the verb, on the noun, and with quantifiers. Detailed looking-time analyses suggest that the arrays begin to be differentiated on the child's hearing are or is. Twenty-four-month-olds failed when number was marked on the noun alone, whereas 36-month-olds succeeded in this condition. These data suggest that infants first come to understand the semantic force of the singular-plural distinction in the months just before their 2nd birthday and that the 1st linguistic expressions of the distinction they understand are on verbs and perhaps on quantifiers.