Agreement Marking May Facilitate Noun Class Learning in Children But Not Adults.

Agreement, defined as the systematic covariance between elements (e.g., between the 3rd person singular subject she and the -s verb ending in 'she writes'), is present in many languages despite introducing redundant complexity. A prominent hypothesis suggests that the ubiquity of complex morphological features such as agreement might be attributable to a functional advantage it provides specifically to child learners (Lupyan & Dale, 2010). We tested this hypothesis through two artificial language learning experiments involving both children and adults. In both studies we compared noun class learning in artificial languages with and without agreement marking. While no overall advantage of agreement in noun classification was observed, our findings indicate that agreement may have a differential effect on children and adults. Specifically, agreement may facilitate the generalization of noun classification to novel nouns in children, but not in adults. These findings add to the growing body of evidence that highlights differences in the cues children and adults rely on in language acquisition. We discuss the implications of these results for theories of language acquisition and language change.