Deuchar & Quay's Bilingual acquisition addresses theoretical issues both of language acquisition in general and of specifically bilingual acquisition through an examination of a case study involving one child's acquisition of English and Spanish in England. Regarding the first issue, the authors attempt to answer questions of phonological differentiation based on acoustic evidence, lexical differentiation in relation to the idea that children avoid lexical synonymy in early stages of language acquisition, and lexical categorization of two-word utterances and the emergence of language choices. Regarding the second issue, they are concerned with the question of whether children possess one or two language systems, and they explore the criteria involved in making such a distinction. Finally, they investigate the factors of the language situation that influence a child's language choice.

This book is composed of seven chapters, with numerous figures and tables. Chap. 1, the Introduction, argues for employing a case study approach, drawing on the works of Jennifer Platt and Esther Dromi, among others, and it sets up the details of the case under analysis. The authors position themselves as methodologically opposed to the prescriptive approach taken by prior researchers such as Vihman & McLaughlin and Harding & Riley, who focus on parental methods strategically designed for bring up a bilingual child. Instead, Deuchar & Quay take a descriptive approach, preferring to examine their data and those of other studies objectively, without characterizing how parents can raise a child to be bilingual. Additionally, Deuchar & Quay prefer not to couch their data in terms of language dominance, owing to the inconsistencies of prior research in determining the defining characteristics of language dominance in bilingual children. Rather, they discuss their data purely in terms of production and environment.

Chap. 2 details the methodology for the case study as it relates to data collection and transcription style. Deuchar & Quay collected both diary data (collected by the mother from when the child was 6 months to 7 years old) and audio/video data (collected from when the child was 4 months to 3 years and 2 months old) within both English- and Spanish-language contexts. For purposes of this case study, the focus is on data collected when the subject (referred to as “M” throughout) was between the ages of 10 months and 2 years and 3 months. M's linguistic environment is differentiated primarily by location. M's mother is a native speaker of British English, and M's father is a native Spanish speaker. The home is characterized as a primarily Spanish-speaking environment, while the child's daycare center at the mother's university is an English-speaking environment. M is addressed in both Spanish and English by her mother depending on their location, primarily in Spanish by her father, and only in English by her grandmother and the daycare facility caretakers.

Chap. 3 investigates acoustic evidence for M's phonological differentiation between Spanish and English. The authors begin by comparing M's acquisition of Spanish and English consonants and vowels with that of monolingual speakers of English and Spanish. However, they find that because of the similarity in the phonemic inventory of Spanish and English and the similarities in the patterns of acquisition of consonants and vowels between monolingual English and Spanish speakers, they cannot determine whether one or two phonological systems exist in M's linguistic repertoire. They therefore move on to a discussion of voicing contrasts in M's production of utterance-initial stops in an English-language context versus a Spanish-language context. Deuchar & Quay attempt to find a corresponding contrast between voice onset time (VOT) characteristic of utterance-initial stops in monolingual English and Spanish language production and in M's production in English- and Spanish-language contexts. They do indeed find a progression leading up to an adult-like contrast in M's acquisition of English utterance-initial stops. Additionally, although they do not find an adult-like contrast in M's acquisition of Spanish utterance-initial stops, using Lisker & Abramson's 1964 categories of voicing in relation to VOT (voicing lead, short voicing lag, and long voicing lag), they do find a contrast within the “short-lag” VOT range. The authors conclude that the acquisition of adult-like voicing contrasts in English shows up in M's linguistic repertoire first as a result of the greater lag differences found in the adult English input versus the Spanish input.

In chap. 4, Deuchar & Quay consider the question of the existence of one or two phonological systems during M's lexical development by examining her ability to produce translation equivalents – two words with the same meaning, one from each language. They begin by a review of arguments for and against the Principal of Contrast proposed by Clark. The Principal of Contrast predicts that children – whether acquiring one or two languages – will avoid synonymy in their lexical development and construct a single lexicon in which maximal semantic contrasts are maintained up to a lexicon of approximately 150 words. Furthermore, Clark argues that bilingual children reject cross-linguistic synonyms, and that translation equivalents are predicted to emerge when bilingual children realize they are dealing with two distinct systems. Deuchar & Quay, in fact, find evidence to the contrary. They find English-Spanish equivalency pairs in M's lexical inventory long before the anticipated age of 2 years, when children's awareness of the existence of two linguistic systems typically emerges – as early as 10 months, with a sharp increase in the acquisition of equivalency pairs at 1 year and 5 months. The authors, however, do not use these data to argue for the existence of one or two lexical systems in young bilingual children; rather, they shy away from positing an answer to this question directly and instead turn to a discussion of language differentiation in relation to facts of lexical development. Deuchar & Quay suggest that the appearance of translation equivalents, though necessary, is not sufficient in establishing lexical differentiation. Here lexical differentiation is not clearly distinguished from pragmatic differentiation, in which the use of lexical items from one language occurs in the appropriate language context. In fact, of interest to sociocultural linguists, Deuchar & Quay posit a high level of influence of language environment on the acquisition of equivalency pairs in bilingual children.

Discussion of the lexicon continues in Deuchar & Quay's examination of the syntactic categorization of M's two-word utterances (chap. 5). They examine both mixed and monolingual two-word utterances in English- and Spanish-language contexts to determine whether M possesses a single initial system. Through a close examination of M's lexical inventory, and therefore of her lexical choices in constructing two-word utterances, Deuchar & Quay find that M more often adheres to the appropriate language in context in producing two-word utterances when her lexical resources allow her to make a choice. The authors therefore conclude that mixed utterances are a result not of a single initial system, but of limited lexical resources. Furthermore, they propose that not all words may be assigned to lexical categories. In particular, function words, such as more/más, appear to operate semantically more like verbs. However, verbal morphology is neither expected nor found in these instances, making a choice of lexical category problematic. Deuchar & Quay refer to these lexical items as “acategorical.” Last, the authors examine morphological constructions in an attempt to determine whether M possesses one or two syntactic systems. They discover that language-specific morphology does appear by 1 year and 11 months. They therefore conclude that at this point M possesses two syntactic systems.

Finally, in chap. 6, Deuchar & Quay consider the issue of language choice and how a case study of bilingual children might contribute to our understanding of the effects of language socialization and richness of linguistic environment on children's language acquisition. Prior sociolinguistic studies have shown that monolingual children often acquire the ability to accommodate to differing registers or varieties at approximately school age. However, Deuchar & Quay's data in this case study clearly show that, at an early age, M is making language choices based on her interlocutors and the location of the interaction. The evidence provided in relation to language choice as early as 1 year and 7 months furnishes us with information difficult to obtain in a monolingual context regarding the ability of young children to make context-appropriate language choices.

The authors also discuss the effect of communicative strategies on M's language choice. By communicative strategies, they refer to M's interlocutors' tendency to accept or reject wrong language choices. The authors briefly discuss methods by which M's parents dealt with an utterance of the wrong language in a particular language context. Several strategies surfaced in their study. Often the mother would provide the translation into the appropriate language for the context, while the father would occasionally act as though he did not understand the utterance in the wrong language choice, provide the utterance translation into the appropriate language choice with a rising intonation, or accept an inappropriate language choice and continue with the interaction. Perhaps most interesting is the authors' proposition that the child's interaction with her monolingual grandmother promoted a bilingual context more often that those with the parents, as a result of the grandmother's acceptance of both Spanish and English utterances in avoidance of communication breakdown. The discussion of communicative strategies in relation to the child's language choices will likely be the most interesting part of the study for sociocultural linguists, but this section of the book is a mere two pages in length. Further development of this portion of their study would not only have lent support to the brief proposition of the role of the environment on lexical differentiation in chap. 4 but would also have contributed to an overall better understanding the role of language socialization in the language acquisition of both bilingual and monolingual children.

Overall, this is an excellent book. Deuchar & Quay's data are interesting and well presented. Their approach to the data and analysis is both clear and convincing. They contribute to both a theory of language acquisition in general and to bilingual acquisition through evidence of phonological differentiation, lexical differentiation, early syntactic development, and language socialization. The book's only drawback is its brief exposition of the seemingly intriguing findings in relation to communicative strategies of the child's interlocutors and the subsequent creation and reinforcement of the language context as it relates to the child's ability to make linguistic choices. Deuchar & Quay's ongoing discussion of the question of one versus two linguistic systems highlights confounding issues in taking an absolute dichotomous stance on this issue. They show that multiple levels of language acquisition must be examined if we are to gain a better understanding of bilingual acquisition. Deuchar & Quay propose a focus on language differentiation and an understanding of linguistic systems as emergent.