Children's expressive and receptive knowledge of the English regular plural

We investigate how children form early grammatical generalizations using the test case of the English regular plural. While some previous studies demonstrate that children apply abstract grammatical rules to produce novel plurals before 24 months, other studies have revealed that children use plural forms inconsistently with familiar and novel nouns and demonstrate limited or variable receptive plural knowledge through 36 months. This is at odds with typical trajectories in language development, where receptive knowledge precedes expressive knowledge. However, previous studies tested receptive and expressive knowledge in different samples and differences in experimental materials across studies limit interpretability. In a cross-sectional design, across three studies, we tested one hundred twenty-eight 24- to 36-month-olds on two complementary experimental tasks: a receptive (eyetracking) task to evaluate children's understanding of plurals and an expressive (storybook) task to test their plural production. In the former, children heard sentences directing their gaze to an onscreen plural or singular target. In the latter, they heard a singular object labeled and a prompt eliciting their plural production. We manipulated both novelty (novel vs. familiar object words; e.g., "cats" vs. "wugs") and phonological form (/s/ vs. /z/ plurals; e.g., "cats" vs. "dogs"). We found strong, age-related evidence of expressive knowledge of the plural, but much more limited evidence of receptive knowledge. Performance on the expressive task only predicted performance on the receptive task that included additional grammatical cues (e.g., "there are two wugs" vs. "can you find the wugs?"). This work highlights the complexity of emerging grammatical generalizations in language acquisition and emphasizes the role of redundant grammatical cues in processing. (PsycInfo Database Record (c) 2026 APA, all rights reserved).