The editors have put together an impressive collection of articles written by leading researchers in the field of first and second language (L1, L2) acquisition. Together, the 17 contributions present a state-of-the-art overview of theoretical perspectives, questions, and methodologies that currently define the field of language acquisition research. Three features of this collection stand out and make the volume a valuable addition to the literature on language acquisition—its interdisciplinary approach, its emphasis on crosslinguistic research, and the breadth of linguistic phenomena under investigation.

The volume opens with four theoretically oriented chapters: MacWhinney’s chapter sets the stage with a concise overview of the debate between nativism and emergentism, providing useful analogies from other scientific disciplines to illustrate the complexities of the emergentist approach with respect to levels of analyses of emergent phenomena and methods used to study them. Van Geert’s chapter introduces a dynamic systems perspective on language acquisition phenomena that affords an understanding of the mechanisms driving acquisition through quantitative modeling of the dynamic interaction between the various components of the system. An example of such an interaction is discussed in the chapter by Christophe, Milotte, Brusini, and Cauvet, who describe empirical data that support a model of how two sources of information—phrasal prosody and function words—can bootstrap children (and adults) into first-pass syntactic analyses of utterances. The first part concludes with a chapter by Thomas, who introduces a novel perspective on developmental disorders by construing them in terms of constraints that shape the acquisition process rather than malfunctioning components of an otherwise normal system.

The second part is devoted to problems of L1 acquisition research. The first two chapters, by Lieven and by Dressler, question our ability to draw conclusions about developmental universals because of the limited crosslinguistic evidence in the field. Lieven summarizes data on morphology acquisition from a number of morphologically rich languages that challenge standard notions, like that of a rule-based default and exceptions, and also discusses how cultural differences in parenting practices may modify the language input available to children, thereby potentially shaping trajectories and time frames of language acquisition in hitherto unexplored ways. Dressler reconceptualizes the notion of typological differences by suggesting a more nuanced view on how different aspects of a language may relate to typological classes (e.g., agglutinating, isolating) in different ways and how this may allow researchers to generate specific predictions about crosslinguistic differences in the acquisition of morphosyntax. The following chapters by Hickmann; Pleh; Jisa, Chenu, Fekete, and Omar; Kail, Cost, and Hub Faria; and Perdue summarize novel empirical findings on crosslinguistic differences in a variety of domains of acquisition, such as spatial language, narrative discourse, online syntactic processing, and L1 and L2 acquisition of verb finiteness. These chapters provide an informative snapshot of the current diversity in terms of languages, methodologies, and linguistic domains that documents the breadth of current language acquisition research.

One of the strengths of this volume is that it gives equal weight to L1 and L2 acquisition, thereby correcting the monolingual bias that has defined language acquisition research for far too long. The chapter by Meisel discusses differences between simultaneous and successive acquisition of two languages in terms of age constraints on the accessibility of universal grammar. Schlyter traces patterns of acquisition of verb morphology in Swedish-French simultaneous bilinguals and shows how differences in frequency of exposure that arise in a bilingual context can account for differences in patterns of acquisition in monolingual children. The chapter by Grainger, Midgley, and Holcomb offers a developmental perspective that can reconcile differences between models of word comprehension for early-stage and later-stage fluent bilinguals. The chapter by de Groot and van den Brink provides a cognitive account for why different novel words are affected differently by retention and forgetting in adult L2 learners. The volume concludes with a chapter by Pallier, who discusses factors that may affect neural representation of L1 and L2s as well as neuroanatomical prerequisites for individual differences in L2 learning.

The editors of this volume should be commended for assembling such an impressive selection of contributions that are representative for breadth and diversity of contemporary language acquisition research. Despite this breadth and diversity, a coherent picture emerges of a rapidly expanding field of research that is gaining a deep and nuanced understanding of how neurophysiological, cognitive, and linguistic systems interact during language acquisition in various domains and contexts.