Produced, but not 'productive': Mandarin-speaking pre-schoolers' challenges acquiring L2 English plural morphology

It is often assumed that pre-schoolers learn a second language (L2) with ease, even for structures that are absent in their L1, such as Mandarin-speaking pre-schoolers learning L2 English grammatical inflections (e.g., ducks, horses). However, while the results from Study 1 showed that such learners can imitate plural words (age = 3;5, N = 20), Studies 2 and 3 showed that they cannot yet generate or comprehend plural morphology (Study 2: age = 4;8, N = 20; Study 3: age = 4;1, N = 20), raising questions about when this is achieved. These findings have important implications for school readiness, as well as for identifying those at risk of developmental language disorders.