Why is learning the grammar of a second language difficult? The present volume brings together insights from leading researchers, published in the past five years of the journal Language Learning, to identify the multiple factors that combine to challenge learners in attaining full proficiency in a second language. An innovative synthesis of recent research on grammar and second language acquisition. Highlights the importance of transparency in form-meaning relations as well as learners' aptitudes and previous language learning experiences. Shows how diminutives facilitate gender acquisition in Russian. Demonstrates how learners make semantic distinctions in acquiring gender distinction in French. Evaluates the role of phonological short-term memory in the acquisition of gender in a semi-artificial linguistic system. A useful collection for a graduate seminar on psycholinguistic aspects of second language acquisition.