The Acquisition of Heritage Languages is an excellent resource for anyone interested in heritage language development. In her book, Silvina Montrul synthesizes the past twenty years of heritage language research focusing on the grammatical development of heritage languages. A heritage language, as explained by Montrul, is any language that is considered to be a minority language based on its sociopolitical status within the local social context. The author begins the book by defining the heritage language speaker, describing the heritage language community, and detailing the heritage language grammar. Montrul also addresses the varying proficiency levels found among heritage language speakers. The author asserts that not all acquired native languages within the bilingual heritage language context develop equally, and she continues to argue for a distinction between language acquisition and language mastery. Montrul proposes that input exposure, language use, and age of onset of bilingualism are most likely the factors affecting heritage language proficiencies. To support her argument, the author draws on empirical research from heritage language acquisition (HLA), first language acquisition (FLA) and second language acquisition (SLA). Montrul also addresses theories and methods that should be considered when conducting heritage language research. The book concludes with future directions and important implications for educators, policy makers, and researchers for the future of HLA.

The book is also visually appealing as many of the complex ideas are presented and summarized through figures (38) and tables (38), which make the book accessible to anyone that is interested in HLA. For example, the author illustrates the intricate relationship between language dominance and proficiency using one of the figures that makes this important concept accessible to the reader. The book also includes thirty-eight pages of references, nine pages of index and seven pages of author index. Finally, it is important to note that the book includes research and examples from a variety of heritage languages such as Arabic, Chinese, Dyirbal, Greek, Hebrew, Inuttitut, Italian, Japanese, Korean, Portuguese, Russian, and Turkish among others.

In Chapter 1, Montrul explains that this new emerging field of language acquisition is both pedagogically and theoretically of high importance. The author claims that although the heritage language is a native language, by adulthood, heritage language speakers show both a native command of the language, and also exhibit some linguistic abilities resembling those of second language learners’ abilities. As a result, heritage language learners and second language learners end up sharing the same classroom, but do not necessarily share the same instructional needs. This leaves educators uncertain about the best pedagogical practices to use in addressing those differing needs. Furthermore, the author points out that the very existence of heritage language speakers seeking instruction in their native language (i.e. heritage language) challenges a prevalent myth that once a native language is acquired beyond the age of five, it becomes structurally fixed, guaranteeing its speaker full native-like abilities in the language. Research in HLA challenges these assumptions and what we know about native language development. Montrul argues that the study of HLA is not just beneficial to understanding heritage language speakers, but it can also inform FLA, SLA and bilingualism research.

Chapter 2 is dedicated to defining the heritage language, its speakers, and their communities. Montrul defines heritage languages as ‘minority languages co-existing with majority languages, including immigrant languages, national minority languages and aboriginal languages’ (15). Those languages also reflect the heritage language communities: The immigrant, aboriginal, and historical language communities. Rather than providing a definition for heritage language speakers, Montrul provides a list of defining characteristics. The most important characteristics to note are: (i) heritage language speakers are bilingual speakers of at least two languages where one is sociolinguistically a minority language (i.e. the heritage language); (ii) heritage language speakers vary in their proficiencies where some only have listening skills, while others may have full native-like abilities; and (iii) heritage language speakers are usually dominant in the majority language. Other types of heritage language speakers that are also important to consider are returnees and international adoptees.

In Chapter 3, Montrul points out commonalities and differences among heritage language speakers and their linguistic abilities in both the heritage language and the majority language. The author first draws a distinction between language dominance and language proficiency. She defines proficiency as what encompasses the linguistic elements of a language such as the phonology, syntax and pragmatics. Montrul also adds that proficiency is not separate from dominance, but it is rather a subcomponent of it. Dominance therefore consists of: Proficiency, language use (e.g. input exposure and type) and a biographical component (e.g. age of arrival and language context). This distinction between dominance and proficiency is crucial for understanding the linguistic abilities of heritage language speakers within the bilingual context. Montrul explains that the general trend among heritage language speakers is that they are typically only dominant in the majority language, but may have varying proficiencies in their heritage languages. Some heritage language speakers may have native-like proficiency in both the heritage and the majority language, while others display low proficiency in the heritage language, but high proficiency in the majority language. Most heritage language speakers are strongest in listening, speaking, reading, and writing in that order.

Montrul also reports on the grammars of heritage language speakers. Montrul reviews over forty studies that looked at vocabulary, inflectional morphology, syntax and interfaces, and phonology. She found that regardless of the social context and the languages spoken, heritage language speakers ‘show strikingly similar patterns of erosion and simplification in vocabulary, morphology, syntax, and interfaces, whereas phonology and pronunciation remains quite strong’ (88) in the heritage language. Montrul explains that the structural differences observed are part of the natural process of language change that occurs in the bilingual context, and although some of these changes in the heritage language grammar are an outcome of language contact, other changes are independent of it.

Chapter 4 presents Montrul’s most significant argument that attempts to explain the observed variation among heritage language speakers’ proficiencies. Montrul first describes bilingual acquisition in general for those readers who are not familiar with the topic, but also specifically addresses the bilingual heritage language context (i.e. simultaneous bilinguals and sequential bilinguals). The author then asserts that two stages of language development exist, an early language development stage and a late language development stage. She emphasizes that FLA research is typically aimed at early stages of language development, focusing on the first five years of a child’s language acquisition. However, based on empirical research, Montrul explains that the linguistic development is a long process. Montrul advances her claim further and makes a distinction between language acquisition and language mastery. The author explains that while acquisition may happen in the early stages of development, mastery and proficiency occurs later, especially after schooling begins. Similarly, a child may begin the acquisition of certain forms in the heritage language but will not fully master those forms by the time he/she begins schooling in the majority language. Consequently, with no instruction in the heritage language, input exposure and language use in the heritage language are substantially reduced, and mastery in the heritage language is difficult to achieve.

If we accept the assumption that acquiring a language is not the same as mastering a language, then Montrul’s claim becomes clear on why the heritage language, the child’s native language, becomes the less dominant language and susceptible to attrition. This leads to what Montrul terms as ‘incomplete acquisition’ or ‘acquisition without mastery’ and in some cases this may lead to attrition or complete language loss. Age, quantity of input, and language use become important individual factors to consider for both language acquisition and language loss. Additional ‘socio-affective’ factors are also discussed.

Before moving forward to support her claims with empirical evidence, Montrul dedicates Chapter 5 and 6 to theories and methods pertaining to HLA research. In Chapter 5, Montrul opposes the call for creating a new theory to study HLA. She believes that current theories popular in SLA and FLA are sufficient. Montrul highlights these major theories – Universal Grammar, Processability Theory, Emergentism, and sociolinguistic theory – and explains their contributions to FLA and SLA research and how they can also contribute to HLA. She also stresses that multiple theories are needed for studying HLA rather than one exclusive theory.

In Chapter 6, the author addresses important methodological factors that should be considered when conducting heritage language research. For example, Montrul asserts that longitudinal studies are preferred in investigating heritage languages; however, due to feasibility many heritage language studies are conducted through cross-sectional design. In addition, Montrul agrees with Grosjean’s (Reference Grosjean1997, Reference Grosjean2008) advocacy for a bilingual approach when studying bilinguals or heritage language speakers rather than the traditional unilingual approach where only one of the languages is investigated. She further explains that because the heritage language is a minority language and the heritage language speaker is mainly dominant in the majority language, it is important to study the interaction and the relationship between the two languages, which is the bilingual approach. Additionally, when conducting research on heritage language speakers, it is essential that background information is collected and described in the study. Montrul states that ‘because sociolinguist situation of heritage language speakers is what defines them, sociolinguistic questionnaires are a must in studies of heritage speakers’ (180). In addition to background information, documenting the proficiency level of the heritage language speakers under investigation is also a must. Finally, Montrul discusses the types of tasks that should be included in the research and the strength and weakness of individual versus group reporting.

In Chapters 7 and 8, Montrul presents empirical studies to support the arguments she makes in Chapter 4. She reports on research that compares heritage language speakers with child monolinguals of the heritage language and child bilinguals of the majority language and the heritage language. She also reports on research that compares heritage language learners with second language learners. Among noteworthy findings, two stand out. First, when investigating language loss or attrition, age and quantity of input seem to be the determining factors in HLA. Quantity of input seems to be more prevalent than quality of input (i.e. the environment and context of how the language is used). Secondly, heritage language learners outperform second language learners in pronunciation and phonological perception as well as in oral tasks; however, second language learners have an advantage over heritage language learners in literacy skills and explicit knowledge of grammar. Chapter 8 addresses additional issues for second language classrooms shared by both types of learners.

The final chapter in the book addresses both scientific and pedagogical implications of HLA research. HLA research is important not just for understanding heritage language but for understanding SLA and FLA. Some of the questions that are posed at the end for future direction are to help researches and educators gain a better understanding of how to create improved classroom assessment tools, understanding how HLA and SLA are similar because most often second language classrooms host both types of learners, and understanding how language attitudes affect heritage language learners.

In conclusion, the book clearly demonstrates the importance of investigating and understanding HLA and how it is similar and yet different from other fields of acquisition. As this is one of the first books to extensively report on comprehensive heritage language issues, it is difficult to identify its weaknesses. However, one issue that can be noted is that although sociolinguistic factors were recognized as essential to HLA research, only a few were mentioned but not extensively addressed. Admittedly, Montrul’s explicit focus is on the grammatical development of heritage languages and it is to be hoped that detailed accounts of sociolinguistic aspects of HLA will emerge from future work. Overall, the book is an outstanding resource in terms of the depth and breadth of its coverage of current issues in HLA. Anyone interested in this area, whether researcher or educator, will find this book to be an excellent starting point for understanding some of the critical issues in HLA research.