With a particular focus on the morphosyntactic features of second language, this book discusses the idea that language acquisition is a discontinuous and 'quantized’ process and thus that some items might be learned twice, statistically and grammatically. It argues that the switch from one way of learning to another is statistically-driven and grammatically motivated. The volume brings together and discusses insights and evidence from learner corpora analysis and electrophysiological data in an attempt to provide the reader with a unified outlook and it suggests a new, developmentally-oriented interpretation of findings. The topics discussed will be of interest to researchers working in the field of psycho- and neurolinguistics and SLA.