Introduction
Fred Genesee McGill University
Internationally-adopted children (IA children hereafter) are a unique population of language learners. They begin learning their first language at birth, indeed before birth, but discontinue exposure to and acquisition of that language when they are adopted by families that speak other languages. Thus, the adopted language becomes their primary and often their only language while their birth language undergoes attrition. On the one hand, IA children resemble monolingual learners insofar as they become monolingual following adoption, in most cases. However, unlike other monolinguals, they have initial exposure to another language, which is discontinued, and their initial exposure to what is sometimes referred to as their second first language (DeGeer, 1992) is delayed in comparison to that of typical monolinguals. On the other hand, they might be thought of as second language learners insofar as they begin to acquire the adopted language after initial exposure to a first language. However, they differ from typical second language learners who usually continue to learn and use their first language once second language learning begins whereas most IA children are exposed to only their second (adopted) language, like monolinguals. IA children share experiences with yet other language learning groups while differing in other important respects. Like children who are born deaf but have cochlear implants, IA children experience delayed exposure to the language, which ultimately becomes their primary language. However, IA children differ from children with cochlear implants who were born deaf because they have had exposure to language prenatally and following birth whereas children born deaf are typically deprived of exposure to language prior to cochlear implantation.
One might ask why the study of language development in IA children is interesting and important since, after all, relative to other childhood language learners, they are a very small population. Understanding the language learning of IA children through research is worthy in its own right for practical and clinical reasons. Clinically speaking, IA children are often thought to be at-risk for language learning for a number of reasons. To begin, they may suffer from perinatal complications, including low birth weight; pre- or post-natal exposure to toxins,
drugs, or other adverse conditions; poor pre- and post-natal care; and physical hardship (Zeanah, et al., 2004). In short, the pre-adoptive care environments in which IA children are initially raised may be inadequate to meet their basic physical, medical, social, and cognitive needs. The degree of deprivation experienced by IA children can vary from mild to extreme and, thus, the consequences of their early environments can similarly vary from mild and short lived to significant and long term (Juffer et al., 2011; Zeanah et al. 2003; see also Rice et al., this volume for more details).
A growing body of research on language development in non-adopted children suggests that early experiences with language shape later development of that language in significant ways (see Pierce et al. this volume) and that first language development during the early months and years of life is important for establishing the foundations for the acquisition of other languages (Kuhl, 2004, 2010). In short, attrition or truncated acquisition of the birth language might be a risk factor for IA children’s development of their adopted language (Johnson & Newport, 1989; Mayberry, 2007). The change in living conditions that IA children experience upon adoption might also be considered a risk factor since it entails a significant difference in socio-cultural, nutritional, physical, and interpersonal conditions for them.
Delayed exposure to the adopted language might itself have significant negative consequences for acquisition of the adopted language (Abrahamsson & Hyltenstam, 2009). Most versions of the critical period hypothesis argue that early language learning, both first and second, is likely to result in “nativelike” levels of competence and that delayed acquisition of language is likely to result in incomplete competence or, at least, competence that differs from that of native speaker monolinguals (e.g., Mayberry, 1993). “Native-like” is often implied, if not explicitly stated, to correlate with monolingualism, a point I return to later. Most research on the critical period hypothesis has focused on delays that occur quite late in development, between 12 and 15 years or age, and later. There is much less evidence concerning the consequences of delayed acquisition in young children. In short, we simply do not know if delays that occur within the first two to three years of life are consequential for children’s eventual language learning outcomes and/or the processes that they deploy to acquire language if onset is delayed.
Notwithstanding these possibilities, there are reasons to think that IA children have certain advantages when it comes to acquisition of the adopted language. More specifically, IA children who are adopted prior to two years of age – common for children from many countries, and especially China – are well within what is considered the classic critical period for language learning, although there is considerable debate about the existence and parameters of the critical period
(Birdsong, 2004). In comparison to second language learners, IA children have the added advantage, as noted above, that their learning time is not divided between two languages. Moreover, many IA children are adopted by older parents who are above average with respect to education and economic status, all factors that are often associated with superior language learning outcomes (Hart & Risley, 1995; Hoff, 2006). Empirical evidence is needed in order to ascertain if, to what extent, and in what ways IA children are at risk or not.
In the same way that it is important from a strictly practical point of view for parents, educators and others who care for any child to understand the typical language learning trajectory of children, it is important for those who care for IA children to know their typical language learning trajectory and the preadoption and post-adoption factors that might affect their growth. It is equally important to have realistic, empirically-based expectations of IA children’s general development, including their physical, medical, cognitive, and personal development. Some IA children will be at risk for or experience language learning and other developmental disorders that go beyond the normal challenges faced by all IA children. Clinicians who work with IA children require solid empirical evidence about typical development in order to better identify those children who are at risk or experience exceptional developmental delays so that they can provide additional support that will meet their developmental needs. The question arises how to distinguish between IA children who are experiencing exceptional language learning difficulties from those who are coping with the challenges of a new language, a new family, and a new environment that all IA children face. Normative expectations based on the development of nonadopted children can provide some useful reference points for clinicians who work with IA children. However, these may not be sufficient and, arguably, may even be inappropriate (see Glennen, this volume) for valid clinical assessment and intervention. Establishing expectations based on norms that are specific to IA children is called for.
These practical and clinical concerns raise important empirical questions: What is the typical language learning trajectory of IA children after adoption –in the short, medium and long term? What factors affect the language learning of IA children: age at adoption, country of origin, quality and nature of the pre-adoption learning environment (foster versus institutional care), health status at the time of adoption, and others. Do IA children achieve parity with non-adopted children, in what domains of acquisition, and when? What is the normal range of variation in language learning outcomes among IA children? How can we distinguish IA children who are at-risk for or experience language impairment from IA children who are simply struggling learning a new language in a new family?
IA children also provide researchers with opportunities to study issues of broad theoretical implication that arise as a result of their learning experiences: How resilient is the language development of IA children who experience early deprivation and adversity? How resilient is their cognitive development following adoption and what are the consequences of cognitive delays for language learning? Is learning of the adopted language by adoptees affected by their greater cognitive maturity when they begin acquiring that language in comparison to monolingual children? Do IA children experience total attrition of their birth language? What about neuro-cognitively – is there evidence of underlying traces of the birth language after adoption (see Pierce et al., this volume)? In a related vein, what are the neuro-cognitive processes that underlie acquisition, processing and use of the adopted language – are they the same as those found for monolingual native speakers or like those of other early second language learners? Does attrition or discontinued acquisition of a birth language influence subsequent language acquisition and why (see Delcenserie, this volume)? Does early delay in exposure to language affect acquisition of that language, to what extent, and in what ways? Does the language development of IA children resemble that of first or second language learners? And, how do we interpret differences, if any, between IA and non-adoptive children in language competence?
Until the late 1990s, there was a tendency for language acquisition researchers to focus on monolinguals and, primarily, learners of English. In contrast, research on language development in IA children is part of a general trend during the past 20 to 25 years to examine language learners with varied language learning experiences. This has included children acquiring two languages simultaneously or successively, children with an impaired capacity for learning language, learners of signed languages, children with cognitive and/or perceptual handicaps, among others. Findings from such research are broadening our empirical knowledge about language learning and enriching our theories of language acquisition. Theories built on evidence from monolinguals cannot provide a complete and generalizable theory of language acquisition in its multiple forms and, thus, risks distorting our understanding of how language learning takes place under diverse conditions. In particular, it risks depicting language learning in non-monolingual contexts as deviant or deficient, rather than simply as different. Once one begins to look closely at different kinds of child language learners, one becomes acutely aware of the diversity of experiences that learners face and of the enormous plasticity of the language learning capacity of young learners. Research on the language development of IA children can contribute to our unfolding and ever-expanding understanding of children’s capacity for language learning. It is in the differences they present in comparison to typically-developing monolingual children that IA children can help us better understand language learning in general.
Studying language learners in diverse learning environments is not without its methodological challenges. Considering research on IA children more specifically, a number of methodological challenges arise. IA children have very varied backgrounds that can differ with respect to age of adoption, birth language and the extent to which it is similar to or different from the adopted language, and their country of origin. They also vary among themselves with respect to the conditions in which they were growing up prior to adoption (home care, orphanage care, or foster care); their social, nutritional, and physical condition at the time of adoption; and reasons for being given up to the state for adoption or placement in foster care homes. Examining these issues systematically is complicated by the fact that it can be difficult, if not impossible, to ascertain valid and precise information about some of these factors from the home countries of IA children. Faced with inadequate information about some of these background issues, researchers may unwittingly include children with diverse backgrounds. Researchers may deliberately include children with diverse background characteristics in order to ensure adequate sample sizes but, as a result, have difficulties later on with interpretation and generalizability of their data. Moreover, there is the question of what is the most appropriate frame of reference for interpreting the results of IA children. The same issue arises in all research on language development in children who are not monolingual language learners, such as simultaneous bilinguals. To date, researchers have tended to use two comparison groups in studies of IA children–same age children who comprise the norming group for standardized tests and questionnaires (like the MacArthur Communicative Development Inventory; Fenson et al., 1993) or typically-developing non-adopted monolingual children who are matched to IA children in particular studies on measures of gender, age, and socio-economic status (see for example, Cohen, Lojkasek, Zadeh, Pugliese, & Kiefer, 2008; Gauthier & Genesee, 2011). While the former can tell us how well and to what extent IA children acquire language like monolinguals, the latter can tell us to what extent the language development of IA children resembles that of monolingual children who are raised in equally favorable learning environments. When each of these frames of reference is appropriate and in what ways is revealed in a number of the chapters in this volume (Delcenserie, Finet et al., Glennen, and Norrman et al.).
The present volume
Language development does not take place in isolation of other aspects of children’s development and, thus, understanding the general background within which IA children develop is important for understanding their language development
specifically. This is particularly true for IA children given the unique, complex, and varied nature of their pre-adoption and post-adoption experiences. Thus, the volume begins with two chapters that are intended to provide readers with the big picture so that they are better able to understand research on the language development of IA children that is reviewed in subsequent chapters.
Chapter 2 by Rice, Jackson, Mahoney and Tan focuses on the pre-adoption environments of IA children from the perspective of risk, stress, adversity and resilience. As they note, the institutional care that many IA children experience can be viewed as “a series of major environmental failures that are at odds with children’s developmental needs” (p. 3). That the quality of institutional care is so important and can put adopted children at risk arises from the fact that during the infant/toddler stage of development, children undergo particularly rapid and critical changes that set the stage for later long term development. Rice et al. consider the child’s developmental needs with respect to basic physical/medical, social/personal, and neuro-cognitive issues. Importantly, they point out that not all institutional care is equally impoverished and that the long term consequences of institutional care is linked to the severity of deprivation, length of care in the institution, and age at adoption, among other factors. Thus, in studying children in the post-adoption stages of development, it is important to consider the quality of the pre-adoption care they experienced. However, this is easier said than done. Rice et al. encourage researchers to develop strategies to overcome barriers to ascertaining the level of stress and adversity experience by adopted children in order to enhance our understanding of their post-adoption development. While stress and adversity are salient and may be characteristic of the early care environments of many adopted children, resilience and adaptability are equally salient when research on their post-adoption development is considered, a point that is reinforced in subsequent chapters.
Chapter 3 by Finet, Vermeer, Juffer, Bosmans and Bijttebier focuses on the cognitive development of IA children. We felt that it was important to juxtapose research findings on the language development of IA children presented in the remaining chapters against findings on their cognitive development in order to better understand to what extent language outcomes are inter-related with cognitive factors and to what extent the developmental outcomes of IA children might be domain specific. Finet and colleagues provide detailed reviews of four longitudinal natural studies of adopted children, including one on non-international or domestic adoptions. In contrast to these studies, they also review the results of the Bucharest Early Intervention Study, which entailed the random assignment of institutionalized children to foster care, thereby making it possible to examine the effects of alternative forms of pre-adoption care minimizing selection bias. Since both children in the foster care group and those in the group with continuing
institutionalization were assessed prior to adoption, it was also possible to examine the developmental trajectory of children in both groups before and after adoption more accurately; it is rare for studies of adopted children to have pre-adoption assessment information. A meta-analysis by Van IJzendoorn, Juffer, and Poelhuis (2005) is also discussed. The studies reviewed in this chapter provide a broad view of cognitive development, including intelligence quotient (IQ) and developmental quotient (DQ), school achievement, executive function, and others. The authors of Chapter 3 illustrate the complexities of assessing IA children’s development by detailing the alternative comparison groups that these studies used: randomized versus convenience sampling, domestic versus international adoptions, same-age peers in the adoption country versus peers in the country of origin, and children raised by adoptive parents versus children raised by biological parents. Each type of comparison reveals different and important information. At issue in these studies, as discussed by Rice and colleagues, are the developmental risks experienced by adopted children and their developmental resilience in the face of these risks and in response to the remedial environments afforded by their new adopted homes.
The next three chapters focus on findings of studies that have examined language development of IA children. Scott and Roberts (Chapter 4) review research on IA children from birth to 5; that is, during the pre-school years. The primary issue for this age group is how they manage the transition from the birth language to the adopted language and, more specifically, to what extent and how quickly they demonstrate the same levels of competence as non-adopted monolingual children and what factors might affect their development, such as age at adoption. These studies are motivated, once again, by the general concern that IA children may be at-risk for acquisition of the adopted language; thus, documenting their language outcomes during this early phase of adoption is critical. Fundamentally at issue is how resilient IA children are in the face of possibly impoverished preadopted care, disruption in exposure to the birth language, and potentially traumatic transitions to a new linguistic and cultural environment. Scott and Roberts provide detailed reviews of findings according to domain of development, including pragmatic, phonological, lexical and morpho-syntactic, broken down by type of measurement – including global and discrete measures in specific domains and results from standardized language tests and parent-report measures. Comparing results across measurement types is important to determine the reliability of findings from different studies that use different measurement methods. Scott and Roberts conclude by saying that while we have learned a lot about IA children’s language during the pre-school years, there is a need for additional research with greater breadth to cover the full range of language skills, especially pragmatic and morpho-syntactic. Research with more depth in all domains is also called for
In Chapter 6, Norrman, Hyltenstam and Bylund pursue the language development of IA children by examining their language abilities as adults. The authors document that many adults who were adopted internationally as children attain very high levels of proficiency in the adopted language – sufficiently high to pass as native speakers of the target language in their day-to-day lives. However, they argue, when you examine their competence in the adopted language carefully, it is possible to discern subtle differences that distinguish them from native speakers. While the lens problem of how best to study and interpret the language performance of IA children was first identified by Scott and highlighted by Glennen in her chapter, it emerges again in Norrman and colleagues’ chapter as they seek to go below the surface and identify the nature of language development in IA children. They conjecture that the differences that they and others in this volume have seen in the language performance of IA children and adults in comparison to test norms and matched non-adopted controls may in fact indicate that the language development of IA resembles that of second language learners.
The focus changes in Chapter 7 by Glennen to clinical issues. As noted at the beginning, IA children are often considered at risk for language development. On the one hand, and contrary to these fears, most IA children transition to their new language quickly, especially children who are adopted at relatively young ages. More specifically, most IA children score within age-appropriate ranges on standardized tests of language and academic achievement. On the other hand, it has been found that there is a larger than expected subgroup of IA children who score below the typical range and, as well, there is a high incidence of referrals of IA children for speech and language services, discussed in greater detail by Glennen. Identifying IA children who present with language difficulties that cannot be accounted for by their delayed exposure to the adopted language or by the normal range of individual differences that is found among all language learners is a complicated matter. Chief among these is what standards of ability are appropriate and valid for identifying children who need additional support. IA children are not native speakers of the language and, thus, strictly speaking, standardized tests that use monolingual native-speakers norms are not appropriate. Even standards that might be established for bilingual or second language learning children are not appropriate because, unlike these learner groups, IA children do not retain their birth language (see Pierce et al., this volume, for more discussion of this issue).
Glennen proposes an alternative strategy for identifying IA children with impaired language development – one that relies on locally-derived norms based on the performance of other IA children. She describes a norming project she has carried out for many years in the U.S. that illustrates the value of this approach. She also describes in some detail the results from that project and how
those results can assist clinicians in identifying IA children with impairment. She then discusses specific issues that require special attention when identifying IA children who might be in need of additional support and how formal identification criteria can differ from region to region. This chapter ends with a consideration of intervention for both IA children who meet official criteria for speech and/or language impairment as well as children who fall outside official guidelines but might nevertheless benefit from additional support in school. Glennen points out throughout this chapter that understanding the language development of IA children, especially on the part of speech and language specialists, poses a lens problem – that is, through what lens do we judge their performance in order to make the most appropriate decisions.
The volume ends on a neuro-cognitive note with a chapter by Pierce, Genesee, and Klein. A number of researchers report that IA children undergo rapid loss of the ability to speak or understand their birth language within months of adoption (e.g., Gindis, 1999; Nicoladis & Grabois, 2002). If true, this might reflect a possible form of neural plasticity whereby early neuro-cognitive traces of the birth language are erased or lost when they are no longer useful, thereby creating a neuro-cognitive state for learning the adopted language that is akin to that when children typically learn their first language. In the final chapter, Pierce, Genesee and Klein provide an in depth review of evidence for and against loss of the birth language. This includes a discussion of behavioral research on language loss and retention in other language learners who discontinue exposure to the birth language, studies of IA children relearning their birth language, and neuro-imaging studies of language processing in IA children. Notwithstanding reports of attrition of the birth language, Pierce and colleagues present evidence that the birth language may, in fact, be retained to some extent. In particular, they present results from their recent neuro-cognitive studies of IA children from China who had learned French as an adopted language. They examined the neural substrate for processing both the birth language (Chinese) and the adopted language (French), neuro-cognitive processing of both the birth and adopted language in IA children. The goal was to determine if there were neural traces of the birth language some 12 years after adoption with no exposure to Chinese and if processing of the new language differed from that exhibited by monolingual learners of that language. They argue that, taken together, these results have important implications for understanding the language learning trajectory of IA children and may help explain behavioral evidence from IA children that points to some weaknesses in comparison to monolinguals. They also explore the theoretical implications of these findings for understanding the impact of early language learning experiences on later language development in general.
Summing up
The chapters in this volume provide comprehensive and detailed reviews and discussions of the diverse lines of research that have been undertaken on internationally-adopted children to date. Two issues stand out that permeate much of this work; namely, developmental resilience and the importance of early experiences for later development. Most authors conclude that most IA children exhibit remarkable resilience despite both significant change and deprivation during the first year or two of their lives. Specifically, there is extensive evidence that, on average, IA children score within the typical range on standardized tests of language and cognitive ability (see Scott & Roberts, Delcenserie, Norrman et al., Glennen, this volume). This is accomplished very quickly in the case of children adopted before approximately one year of age and takes somewhat longer in children adopted at older ages. However, not all IA children are so fortunate. In their pioneering research on adoptees from Romania, Rutter and his colleagues found that even six months of exposure to extreme deprivation after birth can have long lasting and negative consequences on adoptees’ development (e.g., Croft et al., 2007; Rutter, Sonuga-Barke, & Castle, 2010). In other words, early experience matters. Indeed, there is evidence throughout these chapters that, notwithstanding remarkable resilience, the early experiences of IA children can have significant influences on their later development, even when extreme deprivation is not an issue. For example, when compared to SES- matched comparison children from family environments that are advantaged to the same extent as those of the adoptive families, IA children often score significantly lower than their non-adopted peers on a variety of language (e.g., Cohen, et al., 2008; Delcenserie & Genesee, 2014a; Eigsti, Weitzman, Schuh, & De Marchena, 2011; Gauthier & Genesee, 2011) and memory tests (e.g., Delcenserie & Genesee, 2014a; Eigsti et al., 2011), as well as on measures of executive functioning (e.g., Eigsti et al., 2011; Loman et al., 2013; see also Finet et al., this volume). Comparison with SES-matched peers might be considered inappropriate because these comparison groups are above average and, thus, represent a statistically improbable and, therefore, unrealistic bench mark. Because these comparison groups are above average, evidence of differences between IA children and these groups should not be interpreted as evidence of clinical problems. Nevertheless, such comparisons give us an indication of IA children’s ability to benefit fully from the enriched environments into which they have been adopted. In addition, detailed examination of the acquisition of specific grammatical features of the adopted language indicates typical acquisition in some respects (see, for example, research cited in Delcenserie and in Glennen, this volume), but lower than age expectations in others, even after many years of exposure to the new language (e.g., Delcenserie & Genesee, 2014b;
Gauthier, Genesee, & Kasparian, 2012; Glennen & Masters, 2002). In a related vein, the results reported by Norrman and colleagues indicate long term differences in certain aspects of language acquisition and processing between adopted and non-adopted individuals. Finally, there is also evidence that the quality of IA children’s pre-adoptive care is important – specifically, IA children raised in foster care tend to exhibit better post-adoption outcomes that IA children raised in institutions (see Finet et al., this volume; Loman et al., 2013).
Before proceeding, it is important to emphasize that these differences are often subtle in nature, not characteristic of all IA children, and are evident usually only when IA children are compared to high performing groups (e.g., Delcenserie & Genesee, 2014a; 2014b, and Cohen et al., 2008) and/or under demanding test conditions (see Scott & Roberts, and Norrman et al., this volume). This is not to say that some IA children do not experience clinical levels of language difficulty and, thus, require the support of professional speech and language specialists; see Glennen, this volume, for more discussion of related issues. Nor does it mean that additional non-clinical support would not benefit IA children who struggle with language below official clinical levels. To the extent that IA children live in families and neighbourhoods with advantaged backgrounds and, thus, may be educated in school environments with many high performing children, additional in–class support might help to integrate IA children who have difficulty keeping up with their non-adopted peers.
In short, and perhaps not surprisingly, early experience makes a difference in the language, and cognitive, development of IA children. These differences raise important and interesting questions about early experience and language development that, to a large extent, are primarily of theoretical significance. More specifically, the question arises what might explain these differences? There are multiple possible explanations. First, they might reflect the limitations of IA children’s preadoptive and, possibly their pre-natal, environments. As has been pointed out repeatedly in these chapters, IA children are often considered at-risk for language development because of the impoverished nature of their pre-adoption environments. It has been argued that whatever pre-adoptive adversity IA children might have experienced, it is likely to have been relatively short-lived and below the level that might result in significant and long-term difficulties of a clinical nature (Gauthier & Genesee, 2011). Otherwise, how could one explain the relatively strong performance of most IA children, excluding the obvious cases of extreme adversity reported by Rutter and colleagues, for example (although see Rice et al., this volume, for a counter-argument). Definitive support for this line of argument is impossible at present since we lack sufficiently detailed and specific information about the pre-adoptive environments of most IA children. Moreover, it could be that the impoverished quality of the pre-adoptive experiences of most IA children
are not of sufficient magnitude or kind to result in clinical levels of impairments, but are sufficient to result in subtle non-clinical effects as noted in the research reported in these chapters.
Two additional possibilities, that are often difficult to disentangle, are attrition of the birth language and/or delayed exposure to the adopted language. While Pallier has argued that attrition of the birth language in IA children “cleans the slate” and allows for full acquisition of the adopted language (Pallier et al., 2003), results reported by Pierce et al., in this volume, argue against this hypothesis. The evidence for neuro-cognitive traces of the birth language that they report suggests that IA children may not acquire the adopted language exactly like monolingual native speakers because the neuro-cognitive systems that are typically recruited to acquire a first language are pre-tuned in the case of IA children to a language that is no longer being acquired. As a result, IA children, while recruiting some of the classical language learning areas of the brain, also recruit alternative neurocognitive systems that differ from those used by monolingual native speakers. In effect, acquisition of the adopted language does not unfold in the same way as in children who acquire language from birth because the neuro-cognitive substrate for language learning is different in the former in comparison to the latter. Norrman and colleagues, this volume, similarly argue that the language development of IA children is more akin to that of second language learners than first language learners, a point we return to later.
Results reported by Delcenserie, Glennen and Finet et al., in this volume, with respect to the verbal memory abilities of IA children suggest that while the distal effect of delayed exposure to the adopted language may be differences in language outcomes in comparison to non-adopted native speakers, the proximal effect might be differences in verbal memory. More specifically, evidence of differences in verbal memory for the adopted language in IA children in comparison to native monolingual speakers of the same languages suggests that their acquisition of the adopted language may be altered by a verbal memory system that is fine tuned to a language that is no longer being acquired. Delcenserie has explicitly hypothesized that it is underlying differences in verbal memory for the adopted language that underlie differences in language development between IA and non-adopted children. Taken together, findings from this body of research raise an even broader question – what does it mean to be a native speaker? Since the dawn of research on language development in children, monolinguals have been used as the gold standard for gauging the language development of all learners. In effect, monolingual competence has become synonymous with native language competence. However, findings from the research on IA children reported in this volume have shown us that even children who begin to acquire a language less than one or two years after birth in relatively advantaged families exhibit differences in comparison to children who
have acquired those languages exclusively since birth. The precise explanation for these differences awaits further research. In the meantime, we must begin to reconceptualise our notion of native language competence to include alternative routes to language learning, such as simultaneous bilingualism, acquisition of an additional language after a first language is acquired, and acquisition of an adopted language after birth. In other words, native language competence takes different forms in different kinds of language learners under different conditions of learning.
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