This volume is a collection of papers presented at the 12th Generative Approaches to Language Acquisition Conference held at the University of Nantes, France, in 2015. Language acquisition, a field of inquiry that has witnessed continuous growth during the past four decades, is central to building a detailed understanding of the human amazing capacity to develop language. The papers gathered here reflect the current research in the field of first, second and heritage language acquisition, addressing a variety of topics in syntax, semantics, phonology and their interfaces, from a wide range of languages such as Tashlhiyt Berber, English, German, Italian, Japanese, Mandarin, European Portuguese, Heritage Portuguese, Romanian, Serbian, Heritage Sign Language, and Yudja. This volume will thus serve as a valuable reference guide to all scholars interested in (first/second/bilingual) language acquisition, multilingualism, heritage languages, sign language, language pathology and impairment, and experimental research in linguistics.