Primary Language Impairment (PLI)

Primary language impairment (PLI), also known as specific language impairment (SLI),¹ is a disorder of language development in children that is not due to hearing, visual, neurological, or motor impairment (Kohnert, Reference Kohnert2010; Leonard, Reference Leonard1998; Rice, Reference Rice, Rice and Warren2004) and affects about 7% of the population (Tomblin et al., Reference Tomblin, Records, Buckwalter, Zhang, Smith and O'Brien1997). This primary impairment of language learning predominantly disrupts the development of grammatical morphology relative to other aspects of language, although lexical, semantic, and pragmatic difficulties have also been observed.² Hallmark characteristics include difficulty with morphosyntax and the acquisition of functional categories, such as tense and inflection (Bedore & Leonard, Reference Bedore and Leonard2005; Bedore & Peña, Reference Bedore and Peña2008; Jacobson, Reference Jacobson2012; J. Paradis & Crago, Reference Paradis and Crago2001), as well as more complex syntactic rules such as those involving syntactic movement and thematic relations (e.g., van der Lely, Reference van der Lely2005). The origin of PLI is highly debated, whether specific to the linguistic domain or more generally attributable to the cognitive-perceptual domain; however, there is general consensus among researchers that the disorder is neurodevelopmental (J. Paradis, Reference Paradis2010a; Rice, Reference Rice2012). By and large, children with PLI begin to speak later than their typically developing (TLD) peers and demonstrate difficulty in processing and, to a greater extent, in production of their language(s) (Leonard, Reference Leonard1998; Peña & Bedore, Reference Peña, Bedore and Schwartz2009). As such, children with PLI are at high risk for concomitant academic and social-emotional difficulties; thus early identification and intervention are crucial (Leonard, Reference Leonard1998; Schwartz, Reference Schwartz and Schwartz2009).

In children who speak two or more languages, assessment and diagnosis of PLI is confounded by two key issues: the heterogeneity of multilingual development and the language-specific characteristics of PLI (J. Paradis, Reference Paradis2010b). First, among multilinguals there is a wide range of achievement in reaching so-called typical developmental milestones in each language for a given age. Variables such as frequency and type of language input, language status, age, and pattern of exposure (simultaneous vs. sequential) can affect children's performance in their languages (J. Paradis, Reference Paradis2010a). Separating typical from atypical language performance in multilinguals is therefore inherently complex, as there is a certain amount of overlap in the errors (e.g., article use) produced by multilingual children with and without PLI, which can make differential diagnosis tenuous (e.g., Anderson & Marquez, Reference Anderson, Marquez and Grinstead2009). Second, how PLI manifests in the developing language learner is dependent upon the properties of a given language and the age of the child. For example, tense-marking morphemes are characteristically problematic for young monolingual children with PLI in English (e.g., Rice, Wexler, Marquis, & Hershberger, Reference Rice, Wexler, Marquis and Hershberger2000), but not in Spanish (Bedore & Leonard, Reference Bedore and Leonard2001). Moreover, similar to the influence of cross-language transfer in second language (L2) learning in TLD, cross-linguistic influences unique to a particular language pairing can affect the pattern of errors observed in L2 learners with PLI (e.g., Leonard, Reference Leonard and Schwartz2009; J. Paradis, Reference Paradis2010a; Verhoeven, Steenge, & van Balkom, Reference Verhoeven, Steenge and van Balkom2012). As a consequence, the linguistic characteristics of multilingual children with PLI may differ from those of monolingual children with PLI (Orgassa & Weerman, Reference Orgassa and Weerman2008; Verhoeven, Steenge, van Weerdenburg, & van Balkom, Reference Verhoeven, Steenge, van Weerdenburg and van Balkom2011).

An in-depth look at skills in all languages informs the process of assessment of multilingual children with PLI.³ Research suggests that a valid diagnostic evaluation should include three key elements. First, in addition to any available standardized testing with multilingual norms, data should be collected from a variety of sources including parent report (J. Paradis, Emmerzael, & Duncan, Reference Duncan, Brunswick, McDougall and de Mornay Davies2010), curriculum-based language assessment, and language sampling (Caesar, Reference Caesar2005; DeLamo, White, & Jin, Reference Caroline and Jin2011). Second, language proficiency should be evaluated for both native and classroom languages in a comprehensive nonbiased assessment that includes measures of language dominance and language proficiency (Caesar, Reference Caesar2005; Caesar & Kohler, Reference Caesar and Kohler2007). Third, the vulnerabilities of each language in multilingual children with PLI may be evident on some tasks and not others; thus a variety of tasks, dynamic as well as static measures, increases the likelihood that the results are representative of the child's current skill level (Bedore et al., Reference Bedore, Peña, Summers, Boerger, Resendiz, Greene and Gillam2012; Caroline & Jin, Reference Caroline and Jin2011; Kohnert, Reference Kohnert2010; Thordardottir, Reference Thordardottir2008; Verhoeven et al., Reference Verhoeven, Steenge, van Weerdenburg and van Balkom2011).

Dynamic assessment is a promising tool for differentiating multilingual children with PLI from TLD. Static assessment examines a child's current linguistic skills, which, in multilingual children with PLI, fall within a wide range of performance. Dynamic assessment measures the rate of change in performance and may provide information about learning strategies, need for prompting or repetition, and insight into children's language-learning difficulties. A recent study suggests that dynamic assessment of word learning in both languages of a bilingual is likely to better identify the relative strength of a child's fast mapping skills as well as potential cross-linguistic transfer (Kan & Kohnert, Reference Kan and Kohnert2012; see also Hasson, Camilleri, Jones, Smith, & Dodd, Reference Hasson, Camilleri, Jones, Smith and Dodd2013; Kapantzoglou, Restrepo, & Thompson, Reference Kapantzoglou, Restrepo and Thompson2012). In addition, the inclusion of information about the learning process (e.g., children with PLI may attend to different features of words) may lead to better identification of multilingual children with PLI (Alt & Suddarth, Reference Alt and Suddarth2012).

Another interesting alternative to differential diagnosis of multilingual children with PLI is the use of code-switching. Iluz-Cohen and Walters (Reference Iluz-Cohen and Walters2012) used a clever, culturally sensitive design to elicit code-switching in children with and without PLI. The children were asked to retell a story in three different sociolinguistic settings: (home) a story told in English to a Hebrew-speaking monolingual puppet, (school) a story told in Hebrew to an English-speaking monolingual puppet, and (doctor's office) a story told bilingually to a bilingual puppet. On the retelling, the group with PLI code-switched more frequently and had longer segments of code-switched speech. In addition, the group with PLI code-switched twice as frequently from L2 to L1 than from L1 to L2, whereas the TLD children code-switched in either direction equally.

An additional aspect of assessment of children with PLI concerns the role of cognitive weaknesses (such as limited working memory, processing speed, attention, and task shifting) in language acquisition (e.g., Leonard et al., Reference Leonard, Weismer, Miller, Francis, Tomblin and Kail2007; Tropper, Reference Tropper2009; Windsor, Kohnert, Loxtercamp, & Kan, Reference Windsor, Kohnert, Loxtercamp and Kan2008). Given the heavy demands on information processing that language learning entails, specific cognitive difficulties can interact with the acquisition of language-specific linguistic structures, such as low salience grammatical morphemes (Hayiou-Thomas, Bishop, & Plunkett, Reference Hayiou-Thomas, Bishop and Plunkett2004). It is unclear to what extent cognitive impairments underlie deficient language acquisition in PLI generally and in multilingual children specifically. At the same time, recent studies on the potential cognitive advantage of multilinguals would predict that multilingual children with PLI could fare better than their monolingual peers (e.g., Bialystok, Craik, & Luk, Reference Bialystok, Craik and Luk2012).

The research on effective interventions for multilingual children with PLI is sparse. A frequent question is which language should be used for remediation purposes. Recent intervention studies with this population suggest that therapy in L1 can facilitate development of L2, and that gains in L2 following bilingual intervention are comparable to those following treatment in L2 alone (Ebert et al., in press; Restrepo, Morgan, & Thompson, Reference Restrepo, Morgan and Thompson2013; Gutiérrez-Clellen, Simon-Cereijido, & Sweet, Reference Gutiérrez-Clellen, Simon-Cereijido and Sweet2012). Ebert et al. compared the efficacy of four treatment conditions administered to bilingual school-aged children with PLI: language treatment in English-only (L2), bilingual treatment (80% Spanish and 20% English), a nonlinguistic-cognitive treatment, and a deferred treatment condition. The children received language intervention targeting skills in auditory comprehension, morphosyntax, and vocabulary for approximately four sessions a week for 6 weeks. The treatment in L2 English resulted in minimal gains in Spanish L1, but bilingual treatment with an emphasis on L1 Spanish resulted in significant gains in English, equivalent to the gains in English made by the English-only group. These results are consistent with those of Restrepo et al. (Reference Restrepo, Morgan and Thompson2013), who found comparable gains in English vocabulary between their English-only and bilingual treatment groups in preschool children with PLI. Moreover, Gutierrez-Clellen and colleagues noted that preschool English language learners with PLI who were the most limited in the development of their L1 benefitted more from bilingual than from L2-only instruction (Gutiérrez-Clellen et al., Reference Gutiérrez-Clellen, Simon-Cereijido and Sweet2012).

Decisions about the language of treatment should be based on the individual cultural and linguistic needs of the child. Support for the stronger language or multilingual support may be initially necessary, but the language needs of the child may change based on the demands of home and school (Thordardottir, Reference Thordardottir2010). These recommendations are, however, problematic for the monolingual clinician who may be the only one available to treat the child. One creative alternative, a computer-interfaced program in Vietnamese and English, was investigated by Pham, Kohnert, and Mann (Reference Pham, Kohnert and Mann2011). The program, administered by a monolingual English-speaking clinician, resulted in significant receptive vocabulary improvement in both languages for a bilingual preschooler. Additional evidence about the efficacy of intervention in one or more languages in children with PLI and the variables that may affect the degree of cross-language influences will contribute to successful clinical decisions.

Reading Disorders

The incidence of reading impairment among English-speakers has been estimated from 5% to as much as 20% (J. Paradis, Genesee, & Crago, Reference Paradis, Genesee and Crago2011; Shaywitz, Reference Shaywitz2003) and its prevalence among speakers of other languages is influenced by cross-linguistic differences (Wydell, Reference Wydell and Wydell2012). The origin of the reading disorder in a biliterate will influence whether reading is similarly or differentially affected in the two languages. Children who have (classic) dyslexia experience difficulty with decoding words or characters. They have poor decoding skills for reading and poor encoding skills for spelling in the absence of significant verbal language difficulties. Their inordinate difficulty with reading and spelling is not due to limitations of cognition, reading instruction, or sensory/motor abilities (Bishop & Snowling, Reference Bishop and Snowling2004; Lyon, Shaywitz, & Shaywitz, Reference Shaywitz2003). The reading problems of multilingual children with dyslexia may therefore be language specific, and the severity of the problem will be influenced by the characteristics of each orthographic system. In contrast, reading difficulties can stem from underlying problems, such as reduced vocabulary, listening comprehension, and working memory, associated, for example, with primary language impairment (PLI)⁴ or with a separate disorder, hyperlexia (precocious decoding skills markedly superior to reading comprehension; e.g., Kennedy, Reference Kennedy2003; Grigorenko, Klin, & Volkmar, Reference Grigorenko, Klin and Volkmar2003). In those cases, the reading problems may be more general, reflective of verbal language difficulties in the two languages (Joshi, Padakannaya, & Nishanimath, Reference Joshi, Padakannaya and Nishanimath2010; Nation, Reference Nation, Snowling and Hulme2008; J. Paradis et al., Reference Paradis, Genesee and Crago2011).⁵ Children who have challenges with both decoding and comprehension will struggle with reading in both of their languages, and the weight of each component may shift dependent upon the relative development of phonological, morphological, and other linguistic skills. These children often fall under the diagnostic umbrella of language-learning disabled.

A principal focus of research on reading disorders in multilinguals has been on mutual and differential symptoms of impairment subject to the orthographic characteristics of the languages and their relative orthographic distance. Although decoding or character recognition is the gateway to reading comprehension, researchers now recognize the important role morphology plays in reading for this population (e.g., Apel & Lawrence, Reference Apel and Lawrence2011). The strategies that readers with and without dyslexia initially use and later establish depend, in part, upon the characteristics of a given orthography. A principal interest has been how the correspondence between the phonological unit and its symbol bears on reading development across languages. Recent investigations highlight key factors to consider when diagnosing and remediating reading disorders in the biscriptal reader.

Writing systems may be described along three continua: two correspondence continua (granularity and transparency) and one accessibility (availability) continuum. Learning to read is influenced by all three continua, as explained by the psycholinguistic grain size hypothesis (PGSH; Ziegler & Goswami, Reference Ziegler and Goswami2005). The first, granularity, refers to the size of the speech unit that is depicted by script, be it a word, syllable, or phoneme. Each writing system is generally categorized along the continuum from coarse (logographic) to moderate (syllabic) to fine (alphabetic).⁶ The second, transparency, refers to the consistency of the correspondence between speech units and script. Finnish, for example, has a consistent letter-sound correspondence and is highly transparent, whereas English has marked inconsistency between letters and sounds and is considered opaque. The third, a reader-dependent continuum, is the accessibility or the saliency of the phonological unit to the reader. For example, words would be the most salient and accessible speech units to a beginning reader, while individual phonemes within a word would be markedly less accessible, making coarser orthographies potentially easier. The more transparent orthographies are also more accessible and easier for readers to learn, as well as less problematic for individuals with dyslexia (Wimmer, Reference Wimmer1993; Ziegler & Goswami, Reference Ziegler and Goswami2005; Zoccolotti, De Luca, Di Pace, Judica, & Orlandi, Reference Zoccolotti, Luca, Pace, Judica and Orlandi1999).

One resulting problem for cross-linguistic comparisons among populations is that diagnostic measures for identifying dyslexia or other reading disabilities vary depending on the orthography (Landerl et al., Reference Landerl, Ramus, Moll, Lyytinen, Leppänen, Lohvansuu and Schulte-Körne2013; Wydell, Reference Wydell and Wydell2012). For example, in more transparent orthographies, dyslexia is manifested by reduced reading rate (Oren & Breznitz, Reference Oren and Breznitz2005; Suárez-Coalla & Cuetos, Reference Suárez-Coalla and Cuetos2012), while reduced accuracy is distinctive in opaque orthographies (e.g., Goulandris, Reference Goulandris2003; Katzir, Shaul, Breznitz, & Wolf, Reference Katzir, Shaul, Breznitz and Wolf2004; Ziegler & Goswami, Reference Ziegler and Goswami2005). Likewise for the granularity continuum, phonological awareness is closely tied to decoding and word recognition in alphabetic languages (e.g., Melby-Lervåg, Lyster, & Hulme, Reference Melby-Lervåg, Lyster and Hulme2012; cf. Duncan, Reference Duncan, Brunswick, McDougall and de Mornay Davies2010), and cross-language transfer of phonological awareness has been demonstrated in alphabetic scripts (e.g., Durgunoğlu, Nagy, & Hancin-Bhatt, Reference Durgunoğlu, Nagy and Hancin-Bhatt1993), whereas morphological awareness appears to be important for logographic scripts (e.g., Chung & Ho, Reference Chung and Ho2010; Wu, Packard, & Shu, Reference Wu, Packard, Shu, Law, Weekes and Wong2009). Thus, although the defining characteristic is difficulty in reading, there is a need to consider criteria unique to each language when comparing groups with dyslexia across languages. As an alternative, neurobiological markers have been discussed in the diagnosis literature (Rezaie, Simos, Fletcher, Denton, & Papanicolaou, Reference Rezaie, Simos, Fletcher, Denton, Papanicolaou, Breznitz, Rubinsten, Molfese and Molfese2012). At the present time, however, the subject of debate is whether dyslexia has a common neurological basis irrespective of the orthography (e.g., Paulesu et al., Reference Paulesu, Demonet, Fazio, McCrory, Chanoine, Brunswick and Frith2001; Paulesu, Brunswick, & Paganelli, Reference Paulesu, Brunswick, Paganelli, Brunswick, McDougall and de Mornay Davies2010) or different underlying brain abnormalities (e.g., Hadzibeganovic et al., Reference Hadzibeganovic, van den Noort, Bosch, Perc, van Kralingen, Mondt and Coltheart2010).

When assessing biscriptal readers, it is important to differentiate reading difficulties in an L2 that may be due to language-proficiency differences from those that are the consequence of dyslexia or other reading disorders (Nijakowska, Reference Nijakowska, Arabski and Wojtaszek2011). The inclusion of dual-language measures of phonological and morphological awareness, nonword and word reading, oral reading rate, reading comprehension measures, spelling, and rapid naming is essential because dyslexia can manifest differently depending on the orthographic system. Within-subject comparisons allow cross-linguistic investigation of biscriptal readers and uniform selection criteria for the study participants. Lindgrén and Laine (Reference Lindgrén and Laine2011a, Reference Lindgrén and Laineb) compared Finnish-Swedish-English trilingual university students with and without dyslexia on reading and writing measures to examine how orthographic depth influences reading problems across scripts. Of the three, Finnish has the most transparent orthography, followed by Swedish, which in turn is less opaque than English. The students with dyslexia and the control group did not differ in comprehension but did differ in accuracy on oral reading in the three languages. Interestingly, the reading rate for the readers with dyslexia increased as transparency increased. Lindgrén and Laine (Reference Lindgrén and Laine2011b) suggested that the absence of reduced rate for these readers in Finnish, the most transparent, may be due to a sacrifice of accuracy for rate. Similarly, Ibrahim and colleagues (e.g., Ibrahim, Eviatar, & Aharon-Peretz, Reference Ibrahim, Eviatar and Aharon-Peretz2007) hypothesized that visual complexity and orthographic transparency affect the process of reading acquisition, providing evidence from children learning to read multiple scripts, such as Arabic and Hebrew versus Russian and Hebrew.

Differential impairment in biscriptal readers with dyslexia helps identify language-specific and language-general processes of reading. Joshi et al. (Reference Joshi, Padakannaya and Nishanimath2010) compared two Kannada-English bilinguals with reading disorders, one with dyslexia and one with hyperlexia, to a group of typical biscriptal readers. Kannada, a Dravidian language spoken in south India, is an alphasyllabary and is highly transparent. The PGSH would predict better reading performance for the participant with dyslexia in Kannada than in the opaque orthography of English, a prediction that appeared to be partially supported by the data. Although he had difficulty reading nonwords in both languages with no apparent advantage for decoding Kannada, the participant with dyslexia did have a higher percentage of word recognition errors in English than in Kannada, due principally to poor irregular word reading. In contrast, the participant with hyperlexia had good decoding skills in his languages but reduced reading comprehension in both languages, as well as concomitant difficulty with listening comprehension.

The simple view of reading (SVR) elucidates the independent but equally important contributions linguistic comprehension and decoding make to the reading process (Catts, Hogan, & Fey, Reference Catts, Hogan and Fey2003; Gough & Tunmer, Reference Gough and Tunmer1986; Hoover & Gough, Reference Hoover and Gough1990). This model helps explain individual differences in reading ability due to weaknesses in one or both of the skills (Kirby & Savage, Reference Kirby and Savage2008; Vellutino, Tunmer, Jaccard, & Chen, Reference Vellutino, Tunmer, Jaccard and Chen2007). However, the SVR does not address additional aspects potentially problematic for reading-disabled readers, such as naming speed or general processing speed (Gustafson, Samuelsson, Johansson, & Wallmann, Reference Gustafson, Samuelsson, Johansson and Wallmann2013; Johnston & Kirby, Reference Johnston and Kirby2006; Ouellette & Beers Reference Ouellette and Beers2010; Tunmer & Chapman, Reference Tunmer and Chapman2012). Nevertheless the SVR model has served to clarify the functions of language comprehension and decoding in developing readers across orthographies (Joshi, Tao, Aaron, & Quiroz, Reference Joshi, Tao, Aaron and Quiroz2012) as well as the contributions of each in readers with disabilities (Joshi et al., Reference Joshi, Padakannaya and Nishanimath2010).⁷

Just as phonological awareness is considered important for decoding and word recognition in alphabetic languages, morphological awareness is linked to word recognition in logographic orthographies such as Chinese (McBride-Chang et al., Reference McBride-Chang, Lam, Lam, Chan, Fong, Wong and Wong2011; Shu, Wu, McBride-Chang, & Liu, Reference Shu, Wu, McBride-Chang and Liu2006; Wu et al., Reference Wu, Packard, Shu, Law, Weekes and Wong2009). In sequential Chinese-English bilingual readers, problems with morphological awareness have been found in poor readers in Chinese (McBride-Chang, Liu, Wong, Wong, & Shu, Reference McBride-Chang, Liu, Wong, Wong and Shu2012) and in both Chinese and English when assessed independently (Chung & Ho, Reference Chung and Ho2010). In addition, morphological awareness has been shown to influence both word recognition and reading comprehension in alphabetic languages, particularly in the higher elementary grades when vocabulary increases in morphological complexity (see Carlisle, McBride-Chang, Nagy, & Nunes, Reference Carlisle, McBride-Chang, Nagy and Nunes2010; Tong, Deacon, Kirby, Cain, & Parrila, Reference Tong, Deacon, Kirby, Cain and Parrila2011). Consistently, children with PLI have a high risk of reading problems—with an incidence of over 50% versus 8.6% in typically developing children—due to difficulties with grammatical morphology and language comprehension (Catts & Hogan, Reference Catts and Hogan2003; Catts, Fey, Tomblin, & Zhang, Reference Catts, Fey, Tomblin and Zhang2002). Morphological intervention has proven effective for a range of students with literacy difficulties, including children with language-learning disabilities, struggling readers, and English language learners (Goodwin & Ahn, Reference Goodwin and Ahn2010).

A relationship between morphological awareness and reading comprehension has been observed for typical readers in languages with dissimilar scripts such as Arabic (Mahfoudhi, Elbeheri, Al-Rashidi, & Everatt, Reference Mahfoudhi, Elbeheri, Al-Rashidi and Everatt2010), Spanish (Kieffer & Lesaux, Reference Kieffer and Lesaux2008), Chinese (Lam, Chen, Geva, Luo, & Li, Reference Lam, Chen, Geva, Luo and Li2012), and Korean-English readers in both languages (Wang, Ko, & Choi, Reference Wang, Ko and Choi2009). For struggling readers, poor morphological awareness has been linked to poor reading comprehension (e.g., Goodwin & Ahn, Reference Goodwin and Ahn2010; Schiff, Schwartz-Nahshon, & Nagar, Reference Schiff, Schwartz-Nahshon and Nagar2011), as well as an inability to use morphological awareness to bolster reading comprehension (Mahfoudhi et al., Reference Mahfoudhi, Elbeheri, Al-Rashidi and Everatt2010). However, in biscriptal readers the morphological feature that transfers and the direction of transfer is dependent upon the similarities of morphological characteristics between the languages (Pasquarella Chen, Lam, Luo, & Ramirez, Reference Pasquarella, Chen, Lam, Luo and Ramirez2011). For example, Pasquarella et al. (Reference Pasquarella, Chen, Lam, Luo and Ramirez2011) found that an awareness of compound words in English appeared to facilitate Chinese word reading in Chinese-English typical readers, likely, the authors suggest, because compound words are an important part of Chinese vocabulary and are similarly formed in the two languages. In contrast, awareness of English derivational morphology was not related to Chinese vocabulary, as Chinese has few derived words.

The limited findings available to date from studies in biscriptal readers with reading disorders suggest that cross-linguistic transfer following reading intervention can occur in either direction (Swanson, Hodson, & Schommer-Aikins, Reference Swanson, Hodson and Schommer-Aikins2005; Vaughn et al., Reference Vaughn, Linan-Thompson, Mathes, Cirino, Carlson, Pollard-Durodola and Francis2006); however, the nature of this transfer is not well defined. In a recent study Abu-Rabia and Bluestein-Danon (Reference Abu-Rabia and Bluestein-Danon2012) gave 20 sixth-grade Hebrew-English poor readers 40 hours of intervention over a 5-month period in their L2 (English) and assessed their reading skills in both their languages pre- and postintervention. The authors noted improvements in the children's phonological, morphological and syntactic awareness, reading fluency, and nonword reading in both languages, suggesting cross-linguistic L2 to L1 transfer; whereas orthographic-specific skills showed improvement only in L2-English, the language of instruction. Reading intervention studies for multilingual poor readers are needed, including those with better controls, larger sample sizes, different language pairings, and a variety of intervention methods.

Autism

Autism spectrum disorder (ASD) refers to a heterogeneous group of developmental disorders with deficits in verbal and nonverbal communication and restricted or repetitive patterns of behavior in the absence of a general developmental delay (Diagnostic and Statistical Manual of Mental Disorders, 4th ed., text rev.; DSM-IV-TR; American Psychiatric Association, 2000). Although speech and language assessment for children with a diagnosis of ASD will reveal a range of severity of communication impairment, generally children with ASD have marked difficulty with social pragmatic skills and language learning (Gerenser, Reference Gerenser and Schwartz2009). Given these limitations in communication, parents and professionals have expressed concern about whether it is prudent to expose a child with autism to multiple languages. Indeed, parents have been told that multiple languages will confuse the child or even that the child's problems are caused by the multilingual input (Jegatheesan, Reference Jegatheesan2011). Few studies, however, have investigated the outcomes of multilingualism on the language development in children with ASD or the consequences of limiting family interchanges to one language for these children, particularly if family members are not fluent in the selected language. Three recent studies have compared the communication skills in children with ASD exposed to one language versus those exposed to two or more languages and found no evidence for a negative effect of multilingualism; and in one study, some important advantages were found.

Petersen, Marinova-Todd, and Mirenda (Reference Petersen, Marinova-Todd and Mirenda2012) examined the language skills of 14 bilingual (Cantonese- or Mandarin- and English-exposed) and 14 monolingual (English-exposed) children with ASD, age 43–73 months, who spoke a minimum of 30 words. After controlling for the effects of therapy and nonverbal IQ, the two groups did not differ on the receptive or expressive language measures administered in English (or parallel measures in Chinese), suggesting no disadvantage for the children in bilingual homes. Taking bilingual exposure a step further, Hambly and Fombonne (Reference Hambly and Fombonne2012) looked at the timing of language exposure by testing 75 children (age 36–78 months) divided into three groups: two groups of bilingual-exposed children (one simultaneous [before 12 months of age] group and one sequential [after 12 months] group) and a monolingual group. The three groups performed similarly on the (dominant) language measures, suggesting that bilingualism did not disadvantage the language development of these children with autism, nor did the timing of the (L2) exposure. Similarly, Ohashi et al. (Reference Ohashi, Mirenda, Marinova-Todd, Hambly, Fombonne, Szatmari and Thompson2012) found no negative effect of bilingualism when they compared the language abilities of English-French bilingual children who had been recently diagnosed with autism with typical bilingual learners and English-exposed monolinguals with autism matched by IQ. The assessments were conducted in the (dominant) home language. With the effects of any previous intervention hours co-varied, the groups did not differ on any of the language measures of receptive, expressive, or functional communication skills. These results also suggested no language-learning disadvantage for the bilingual children with ASD, even prior to substantial intervention.

The results of these studies thus do not support the recommendation, often made by professionals, to limit input to the child with ASD to one language (Kay-Raining Bird, Lamond, & Holden, Reference Kay-Raining Bird, Lamond and Holden2012; Kremer-Sadlik, Reference Kremer-Sadlik2005). Moreover, parents prefer raising their children multilingual regardless of their impairments. In her investigation, Jegatheesan (Reference Jegatheesan2011) reported that parents were counseled by teachers and professionals to speak only one language to their children—English. (This contradicts the formal recommendation by the International Association of Logopedics and Phoniatrics [IALP] that the home language should not be changed; Fredman & Centeno, Reference Fredman and Centeno2006). The families considered the request unreasonable because many family members were not fluent in English, and following the professionals’ recommendations would have essentially cut the child off from family life. Therefore, the parents hid their child's multilingual exposure from the professionals in charge of their child's education. Of note, by the end of the interview project, the children had made significant progress: The author and families observed a marked reduction in tantrums and all three boys were conversing in three languages.

Furthermore, Jegatheesan (Reference Jegatheesan2011) carefully explored the cultural and individual issues underlying the decision of three South Asian Muslim families who had immigrated to the United States to raise their child with ASD as multilingual. Using ethnographic interviews, observations, and fieldwork over a period of 17 months, Jegatheesan investigated the families’ cultural practices and the parents’ beliefs about multiple language acquisition. According to the study, the families’ beliefs were shaped by their Islamic faith, which emphasized full inclusion of children with disabilities in all family and community activities to enable them to overcome their limitations. An essential part of family life was interacting with family and friends, most of whom were multilingual and freely code-switched. The children's exposure to all languages was considered important for participation in family events and other religious and community activities, and learning and praying in Arabic was central to their Muslim identity and religious practices. As well, the families wanted their children to speak in English to be able to interact in the school and community. One parent, concerned about her son's disruptive behavior and need to practice English, talked about taking her son to the stores late at night when there were fewer people so she could teach him to talk to the staff in English and the staff might have more time to respond.

Kay-Raining Bird et al. (Reference Kay-Raining Bird, Lamond and Holden2012) surveyed 49 parents of children with ASD who were members of a multilingual family, of which 75% were raising their children to be multilingual.⁸ These parents selected reasons for raising their children with ASD bilingually: communication with family and friends, living in a bilingual city or country, and the life and job opportunities that would be available to them. Concerns that were expressed by those who had decided to maintain a multilingual home included the lack of professional help and/or access to services, the lack of support from family and friends, and the worry that the child would be confused or find learning languages too difficult. Interestingly, of these parents, 97% of the respondents providing bilingual input to their child and 89% of those providing monolingual input considered becoming bilingual for their child with ASD equally or more important as for their sons or daughters who were typically developing.

In sum, the evidence suggests that exposing a child with ASD to multiple languages does not hamper language development, and instead fosters the child's ability to communicate with immediate and extended family members. Moreover, training is sorely needed to ensure that professionals make culturally sensitive recommendations based on empirical evidence.

Down Syndrome

Down syndrome (DS) is a genetic condition caused by a mutation in cell division (Trisomy 21) resulting in a developmental phenotype that includes mental retardation and speech and language delay, among many other difficulties. The incidence of concomitant hearing loss, commonly conductive, is high (34%) in the critical first year of life (Raut et al., Reference Raut, Sriram, Yeoh, Hee, Lim and Daniel2011) and is often an ongoing problem. Rate of speech and language development seems to parallel nonverbal cognitive development initially, though a gap between communication and cognitive skills soon emerges that widens over time, with progressively more advanced nonverbal skills (Chapman & Hesketh, Reference Chapman and Hesketh2001). Yet the weaknesses in verbal development are not uniform. Speech intelligibility difficulties are often evident, receptive skills surpass expressive, and vocabulary knowledge is characteristically stronger relative to compromised morphosyntactic skills (Chapman, Reference Chapman2006; Dodd & Thompson, Reference Dodd and Thompson2001).

Few studies published to date have looked at the effect of multilingual input on children with DS. Kay-Raining Bird and colleagues (Kay-Raining Bird, Reference Kay-Raining Bird2009; Kay-Raining Bird et al., Reference Kay-Raining Bird, Cleave, Trudeau, Thordardottir, Sutton and Thorpe2005) compared children who were bilingual and monolingual with DS to those who were typically developing and matched for developmental level. Similar to prior studies, the children with DS showed evidence of an expressive language weakness relative to the TLD children. Critically, the bilingual and monolingual groups with DS did not differ on any of the language measures including receptive and productive vocabulary, MLU (mean length of utterance), and number of different words, implying no inherent bilingual disadvantage for language learning in children with DS. The authors noted a considerable range of performance in the less dominant language among the bilingual children with DS; in a subsequent study, Feltmate and Kay-Raining Bird (Reference Feltmate and Kay-Raining Bird2008) investigated whether some children with DS had more difficulty than others in learning a second language, accounting for this wide performance range. From an in-depth look at the morphosyntactic and vocabulary skills of four English-French bilingual children with DS matched in triads, each with a monolingual child with DS and a developmental-matched bilingual TLD, the investigators noted that a receptive-expressive performance differential was present to a similar degree in both English and French. In addition, the individual differences in relative dominance and L2 production observed for the children with DS appeared to be related to the exposure time to the L2. Although the children with DS performed better on receptive than expressive skills overall, three of the four DS bilingual children demonstrated English dominance in expressive but not receptive vocabulary. Notably, some of these bilingual children with DS outperformed their TLD peers on a few of the expressive measures, demonstrating the ability not only to acquire two languages, but also to do so in an area of relative weakness.

Bilingualism across modalities was investigated in a set of monozygotic twins with Mosaic DS at 10 years of age and again at 16 years of age (Woll & Grove, Reference Woll and Grove1996; Woll & Morgan, Reference Woll and Morgan2012). The parents were both deaf and members of the deaf community. The twins, simultaneous bilinguals, communicated with their parents in British Sign Language (BSL), with the hearing community in English (including an older brother), and between themselves in both, although they used English exclusively if no deaf individuals were present. The girls differed in the extent of their language deficits, but their patterns of difficulties were consistent across languages. For both girls, their BSL and English receptive skills were stronger than expressive skills, and they tended to score higher in BSL than English vocabulary comprehension at 10 years of age. The sign language advantage was even more pronounced at 16 years of age (Woll & Morgan, Reference Woll and Morgan2012).⁹ The morphosyntactic weakness reported for monolingual children with DS was similarly noted in the twins’ languages and they demonstrated greater difficulty in both BSL and English as morphosyntactic complexity increased.

If bilingualism poses no inherent disadvantage for children with DS, does multilingual input confer an advantage? Are the cognitive benefits of bilingualism that have been suggested for TLD individuals (Bialystok & Martin, Reference Bialystok and Martin2004; Bialystok & Viswanathan, Reference Bialystok and Viswanathan2009) applicable to individuals with DS? Edgin, Kumar, Spanò, and Nadel (2011) looked at the neuropsychological performance of 41 individuals, ages 7 to 18, with DS. Two groups with equivalent age, gender, IQ, and socioeconomic status were compared, a monolingual (n = 28) group and a bilingual (n = 13) group, with the latter exposed to a second language between 1 and 11 hours daily. On testing, which included the Arizona Cognitive Test Battery for DS, Kaufman Brief Intelligence Test—Second Edition (KBIT-II), Behavior Rating Inventory of Executive Function (BRIEF), and the Scales of Independent Behavior—Revised (SIB-R), no significant group differences were found. Although the bilingual and monolingual groups did not differ, suggesting no cognitive advantage for the bilingual group, the study had limitations, some of which were recognized by the authors. Additional language testing beyond that of a parent rating scale (SIB-R), particularly in the less dominant language, would be needed to adequately assess receptive and expressive skills. In addition to daily hours of exposure, other factors should be considered that have been shown to influence language learning, such as the type of input, language status, and the onset of exposure (sequential or simultaneous). It is also possible that the age range in this study was too wide to examine equitably the potential differences. The so-called cognitive advantage of bilingualism also appears to change across the life span (Bialystok, Martin, & Viswanathan, Reference Bialystok, Martin and Viswanathan2005). Bilingual children and older adults show a cognitive advantage that young adults may not (Bialystok, Craik, & Luk, Reference Bialystok, Craik and Luk2008, Reference Bialystok, Craik and Luk2012; Salvatierra & Rosselli, Reference Salvatierra and Rosselli2011).

To conclude, current findings suggest that children with DS can learn multiple languages without negative effects on their dominant or overall communicative abilities. The research on bilingualism and DS has been limited, however, and variability has been found in these children's L2 performance. Feltmate and Kay-Raining Bird (Reference Feltmate and Kay-Raining Bird2008) suggested that children with DS may need more repetition and structured input for effective language learning. The efficacy of bilingual intervention in these children has yet to be explored. Whether or not bilingualism confers a cognitive advantage for people with DS warrants our attention. The potential for enhancing learning during the formative years as well as improving cognitive reserve in individuals with DS who are at greater risk than the general population for acquiring dementia in their elder years (Tyrrell et al., Reference Tyrrell, Cosgrave, McCarron, McPherson, Calvert, Kelly and Lawlor2001) is a worthy rationale.

Aphasia

Aphasia is an acquired disorder of language and communication, resulting from brain damage. Aphasia is caused most often by a cerebral-vascular accident (stroke) in the language-dominant hemisphere of the brain (the left hemisphere in most individuals). Aphasia and related acquired language and communication disorders can also result from closed-head injury, brain tumors, and progressive neurological diseases, as will be discussed below. The disorder can affect all language modalities or selective ones and can range from mild to severe. The extent and the specific characteristics of the impairment are associated with the site and size of the brain lesion. When the lesion is small and the subsequent impairment is mild, complete recovery is, in some cases, attainable; however, most individuals with aphasia do not recover their linguistic and communication skills completely or return to their pre-onset level of functioning. In most cases, gradual improvement continues with time and treatment.

Many multilingual individuals who sustain a single stroke resulting in aphasia experience comparable—or parallel—impairment in all languages (Fabbro, Reference Fabbro2001; M. Paradis, Reference Paradis2004). That is, if they were highly proficient in all their languages prior to the stroke, they show comparable degree of difficulty in all their languages poststroke. Less often, but not infrequently, there is nonparallel pattern of impairment and recovery, when the relative impairment of the languages poststroke does not reflect their relative strength prior to the aphasia onset. For example, one language is accessible more than others, despite comparable proficiency prior to the stroke, or some languages appear completely inaccessible to the speaker poststroke (Albert & Obler, Reference Albert and Obler1978; M. Paradis, Reference Paradis1983).

Variables, such as age of acquisition, levels of proficiency, and patterns of language use have been put forward as predicting factors for which language will show the best recovery; to date, there is evidence that some or all of these variables interact to predict patterns of impairment and recovery in multilingual aphasia, but there is no consensus about their relative roles and the manner in which they interact (Goral, Reference Goral and Faust2012b). For example, whereas in several reports relative comparable impairment was evident in all languages of multilingual speakers who acquired aphasia (e.g., de Diego Balaguer, Costa, Sebastián-Gallés, Juncadella, & Caramazza, Reference de Diego Balaguer, Costa, Sebastián-Gallés, Juncadella and Caramazza2004; Edmonds & Kiran, Reference Edmonds and Kiran2006), for other individuals it was their first-acquired language that was more accessible to them than their later-learned languages (Croft, Marshall, Pring, & Hardwick, Reference Croft, Marshall, Pring and Hardwick2011 [participant 2]; Goral, Levy, Obler, & Cohen, Reference Goral, Levy, Obler and Cohen2006). As well, there have been reports of later-learned languages demonstrating milder impairment than earlier-acquired languages (e.g., Faroqi-Shah & Waked, Reference Faroqi-Shah and Waked2010; Ibrahim, Reference Ibrahim2008). The differential abilities may be manifested in overall language abilities or in selective language skills, such as comparable comprehension impairment but differential production abilities (e.g., Marshall, Atkinson, Woll, & Thacker, Reference Marshall, Atkinson, Woll and Thacker2005 for a bimodal sign-language-English speaker), comparable spoken language abilities versus differential writing impairment (e.g., Kambanaros, Messinis, & Anyfantis, Reference Kambanaros, Messinis and Anyfantis2012, for a Greek-English bilingual), or comparable overall impairment but differential impairment of morphological abilities (e.g., Knoph, Reference Knoph2011, for a trilingual Persian- English-Norwegian speaker).

In some cases, unintentional language switching or mixing of the two languages occurs (Abutalebi & Green, Reference Abutalebi and Green2008). In such cases, multilingual people with aphasia may insert elements from one of their languages while speaking another, even if their interlocutors do not understand that language. This impaired switching ability may occur without the conscious awareness of the person with aphasia. In contrast, the retrieval of elements from the nontarget language could also serve as a strategy to facilitate retrieval of elements in the inaccessible target language (Ansaldo, Marcotte, Scherer, & Raboyeau, Reference Ansaldo, Marcotte, Scherer and Raboyeau2008).

A key question in aphasia rehabilitation, of theoretical and clinical implications, has been whether aphasia rehabilitation administered in one of the multilingual's languages positively affects the untreated languages. The presence or absence of cross-language treatment effects may be indicative of interdependent versus independent underlying representation and processing of multiple languages. Clinically, decisions about language choice for rehabilitation should ideally be informed by research evidence. Here, as in patterns of initial impairment and gradual recovery, variables of language proficiency, use, and linguistic similarities are likely to affect between-language influences. And, here too, studies in multilinguals with aphasia published to date have yielded inconsistent results (see reviews in Faroqi-Shah et al., Reference Faroqi-Shah, Frymark, Mullen and Wang2010; Kohnert & Peterson, Reference Kohnert, Peterson, Gitterman, Goral and Obler2012; Obler & Park, Reference Obler, Park, Gitterman, Goral and Obler2012).

Several findings point to the role of relative language proficiency in cross-language generalization, suggesting cross-language facilitation from a treated language to a comparably recovered language or to a weaker language but a lack of facilitation or—in some cases—negative consequences from a weaker treated language. For example, Miertsch, Meisel, and Isel (Reference Miertsch, Meisel and Isel2009) documented a multilingual individual with aphasia who had comparable poststroke abilities in his L2 English and L3 French and better recovered abilities in his L1 German. The authors found improved performance in L2—but not in L1—following treatment in L3. Similarly, improved grammaticality in language production of a multilingual speaker was documented in French, which was the participant's untreated weaker L3 following treatment in his more recovered L2, English (Goral, Levy, & Kastl, Reference Goral, Levy and Kastl2010). At the lexical level, improved naming performance was found between the two languages of Spanish-English bilinguals with aphasia when the treated Spanish and untreated English were of comparable proficiency (Edmonds & Kiran, Reference Edmonds and Kiran2006). However, the two other participants reported in Edmonds and Kiran showed no generalization from English (the treated language) to Spanish (the untreated, weaker language).

In other studies, a similar lack of cross-language generalization has been documented for treatment administered in the weaker language. Namely, there was no facilitation from treatment in English (a participant's L2) to the untreated French (his first and more dominant language) (Miller Amberber, Reference Miller Amberber2012); nor from treatment in German to the untreated French in an early bilingual with reportedly comparable abilities in his two languages prior to the stroke but a more impaired French poststroke (Meinzer, Obleser, Flaisch, Eulitz, & Rockstroh, Reference Meinzer, Obleser, Flaisch, Eulitz and Rockstroh2007). Evidence for negative cross-language effects following treatment was found in a study by Abutalebi, Rosa, Tettamanti, Green, and Cappa, (Reference Abutalebi, Rosa, Tettamanti, Green and Cappa2009) for a bilingual who was treated in his weaker post-CVA L2 (Italian): His scores in L1 (Spanish) were lower post-treatment in Italian than prior to the treatment.

Two additional variables have been implicated in cross-language results. One is the linguistic context of the individuals. Thus, for example, the language of environment may have affected the relative improvement of the participant reported in Goral, Rosas, Conner, Maul, and Obler (Reference Goral, Rosas, Conner, Maul and Obler2012), who showed marked improvement in English, his less accessible language but the language of environment at the time of the treatment, and no positive effect on his more proficient Spanish. The other relates to similarities and differences between a given pair of languages, a variable mentioned above as a contributing factor to differential impairment in multilinguals. For example, Kohnert (Reference Kohnert2004) demonstrated that improved production in the nontreated language was only evident in cognate words. The influence of language similarities may also explain the results reported in Goral et al. (Reference Goral, Levy and Kastl2010) for French morphosyntactic elements, such as the improvement in pronoun-gender agreement (a feature relevant to both English and French) but not in article-noun agreement (a feature relevant to French but not English), following treatment in English.

By and large, the data currently available from studies of multilingual aphasia can be interpreted within current frameworks of multiple language representation in the brain. These include theories of convergence of brain regions and networks associated with all languages of multilinguals (Abutalebi & Green, Reference Abutalebi and Green2007; Indefrey, Reference Indefrey2006). Proponents of this view attribute any differential sparing and impairment to processes of language control, rather than to a differential representation of the different languages. Moreover, facilitation and inhibition between pairs of languages can be predicted by theories of multiple language activation (Costa, Reference Costa, Kroll and De Groot2005; Kroll, Bobb, & Wodniecka, Reference Goral, Levy, Obler and Cohen2006; Marian, Spivey, & Hirsch, Reference Marian, Spivey and Hirsch2003). For example, the hypothesis that all languages of multilinguals are active and therefore the target language of a given communication intent needs to be activated, whereas the nontarget languages must be inhibited, predicts a processing cost associated with the reactivation of a previously inhibited nontarget language. In aphasia rehabilitation, these patterns of inhibition and activation can manifest in differential accessibility of the languages during and following treatment (Goral, Reference Goral, Gitterman, Goral and Obler2012a).

Dementia

Dementia can be defined as acquired impairments in multiple cognitive domains (e.g., memory, language, orientation, monitoring) caused by brain dysfunction (Mendez & Cummings, Reference Mendez and Cummings2003). Dementia has been associated with degenerative diseases, such as Alzheimer's disease and Parkinson's disease, and with diffuse or multifocal brain pathologies that are considered different from the brain changes associated with healthy aging (e.g., Petersen, Reference Petersen, Iqbal, Sisodia and Winblad2002).

Language and communication impairments accompany many forms of dementia. One common problem is word-finding difficulty (anomia), characterizing dementia of the Alzheimer's type and primary progressive aphasia, as well other types of dementia (Aronoff et al., Reference Aronoff, Gonnerman, Almor, Arunachalam, Kempler and Andersen2006; Mesulam et al., Reference Mesulam, Rogalski, Wieneke, Cobia, Rademaker, Thompson and Weintraub2009; Ober, Reference Ober2002). Specifically, individuals with dementia often fail to retrieve a target word during experimental testing as well as during natural conversation. Circumlocutions (saying “that thing that takes you up and down in a building” for “elevator”), semantic paraphasias (saying “mother” for “daughter”), and empty speech (using words such as “thing” and “this”) are often produced. The anomia may be due to retrieval difficulties and, in some types of dementia, may be associated with semantic impairment (e.g., Mesulam et al., Reference Mesulam, Rogalski, Wieneke, Cobia, Rademaker, Thompson and Weintraub2009; Rogers, Ivanoiu, Patterson, & Hodges, Reference Rogers, Ivanoiu, Patterson and Hodges2006). As well, many individuals with dementia demonstrate impairments in their ability to comprehend complex discourse and in their discourse production (Hamilton, Reference Hamilton2008). Studies typically report the failure to maintain the topic of conversation or to follow a change in the topic, as well as inappropriate use of pronouns and other anaphora (e.g., Almor, Kempler, MacDonald, Andersen, & Tyler, Reference Almor, Kempler, MacDonald, Andersen and Tyler1999; Welland, Lubinski, & Higginbotham, Reference Welland, Lubinski and Higginbotham2002). Morphological and syntactic abilities have been found to be largely preserved in dementia (Kavé & Levy, Reference Kavé and Levy2004; Kavé, Leonard, Cupit, & Rochon, Reference Kavé, Leonard, Cupit and Rochon2007).

An ongoing debate in the literature on dementia concerns the relations among language impairment and deficits in other cognitive domains, such as working memory and executive function. For example, it is possible that the difficulty in maintaining discourse topics and following a conversation is rooted in an attention or memory deficiencies and that instances of anomia may reflect a more general memory decline and an overall decreased executive functioning (e.g., Bayles & Tomoeda, Reference Bayles and Tomoeda2007; Kempler & Goral, Reference Kempler and Goral2008).

Limited attention has been paid to the manifestation of dementia among multilingual speakers in the major, currently available textbooks about dementia. However, there is a small body of recent literature addressing two main questions about dementia in multilingual and multicultural populations. One concerns the so-called bilingual advantage, reported for healthy bilingual individuals. That is, findings suggest that older bilinguals have superior cognitive control abilities as compared to their monolingual peers. For example, Bialystok and colleagues (Bialystok, Craik, Klein, & Viswanathan, Reference Bialystok and Martin2004) found smaller difference between younger and older bilinguals than between younger and older monolinguals on the Simon Test, a task that measures inhibitory control. These data have been partially replicated in additional studies (Bialystok et al., Reference Bialystok, Martin and Viswanathan2005); however, several recent studies have failed to find a bilingual superior performance on tests of inhibitory control, questioning the existence of a bilingual advantage (for a review, see Hilchey & Klein, Reference Hilchey and Klein2011). Nevertheless, other studies support the notion of bilingualism as a factor contributing to cognitive reserve. The notion of cognitive reserve has been employed to account for interindividual differences in the manifestation and rate of cognitive deficits in dementia (Stern, Reference Stern2002, Reference Stern2009). That is, individuals with more cognitive reserve—such as those with high education levels and those engaged in complex mental activities throughout their lives—display measurable cognitive deficits later in the course of the dementia than individuals with lower reserve (Manly, Schupf, Tang, & Stern, Reference Manly, Schupf, Tang and Stern2005). One contributing factor to reserve may be the cognitive practice that bilinguals enjoy throughout their lives (Kempler & Goral, Reference Kempler and Goral2008; Rivera Mindt et al., Reference Rivera Mindt, Arentoft, Kubo Germano, D'Aquila, Scheiner, Pizzirusso and Gollan2008). Consistent with this notion, several studies reported older age of dementia onset for bilinguals or multilinguals than for monolinguals (Bialystok, Craik, & Freedman, Reference Bialystok, Craik and Freedman2007; Kavé, Eyal, Shorek, & Cohen-Mansfield, Reference Kavé, Eyal, Shorek and Cohen-Mansfield2008).

The other question raised in recent studies on dementia in multilinguals asks whether the language impairment that accompanies the dementia is comparable in the two languages of bilinguals or whether the impairment is selective. In that, this question mirrors the one asked about aphasia in multilinguals, as described above. And, similar to the literature on aphasia, here too, published data are mixed, supporting both comparable impairment in some individuals and selective in others.

Mendez and colleagues have reported greater preservation of the first-acquired language as well as selective use of L1 in individuals with dementia (Mendez, Perryman, Pontón, & Cummings, Reference Mendez, Perryman, Pontón and Cummings1999; Mendez, Saghafi, & Clark, Reference Mendez, Saghafi and Clark2004). Support for a selective impairment is also found in reports of bilingual individuals with dementia favoring their first-acquired language, at times using it exclusively, even if inappropriately (De Santi, Obler, Sabo-Abramson, & Goldberger, Reference De Santi, Obler, Sabo-Abramson, Goldberger, Joanette and Brownell1990; Friedland & Miller, Reference Friedland and Miller1999). McMurtray, Saito, and Nakamoto (Reference McMurtray, Saito and Nakamoto2009) have proposed that patterns of uncontrolled reverting to L1 may be an early indicator of dementia. The two patients they reported had been regular users of their Japanese and English and demonstrated a shift to predominant use of L1 prior to developing cognitive impairment later diagnosed as dementia. However, Gollan, Salmon, Montoya, and da Pena (Reference Gollan, Salmon, Montoya and da Pena2010) have demonstrated that greater impairment may be detected in the dominant—albeit not necessarily the L1—of bilinguals with dementia when performance is compared to similar bilinguals without cognitive impairment.

In contrast to the studies that showed a differential preference of the L1, language testing in several cases of dementia revealed parallel impairment of both languages. This was the case for one Spanish-English bilingual (Hernández, Costa, Sebastián-Gallés, Juncadella, & Reñé, Reference Hernández, Costa, Sebastián-Gallés, Juncadella and Reñé2007) and four Japanese-Portuguese bilinguals (Meguro et al., Reference Meguro, Constans, Shimada, Yamaguchi, Ishizaki, Ishii and Sekita2003). In these studies, there were no significant differences between performance in the first and second languages of individuals who acquired dementia. Yet, despite overall comparable levels of impairment, language-specific characteristics appear to influence the manifestation of the impairment in each language. For example, the reading performance of the bilinguals in Meguro et al. was virtually intact when faced with Japanese Kana writing (the writing system with a shallow grapheme to phoneme correspondence) and with Portuguese words that had regular spelling, but more impaired when presented with words written in Kanji (the less transparent writing system, based on Chinese characters).

In summary, the study of language impairment in multilingual individuals with dementia is at an early stage, and its results do not point to uniform pattern of parallel or selective impairment. Preliminary findings suggest that bilinguals may benefit from cognitive advantages over their monolingual peers at the onset of the manifestation of cognitive impairment associated with dementia. There is no published evidence to date on language treatment in individuals with language impairment associated with dementia.

Traumatic Brain Injury (TBI)

Little is known about the manifestation and recovery patterns of the languages of multilingual speakers following acquired language impairments resulting from a traumatic brain injury (TBI). Individuals who sustained a TBI may experience mild, moderate, or severe cognitive impairment. The severity and type of impairment is associated with the size and location of the damage to the brain and with the duration of loss of consciousness. Two hallmark language difficulties of TBI are word-finding difficulties and impaired discourse abilities. As in dementia, some deficits may be viewed as specific to language and others may be secondary to other cognitive impairments, such as impaired attention, memory, monitoring, and organization skills (Coelho, Reference Coelho2002).

If the acquired brain injury occurs during childhood, brain plasticity typically will allow for neuronal reorganization and thus for adequate, if not complete, recovery of most language skills (Chilosi et al., Reference Chilosi, Cipriani, Pecini, Brizzolara, Biagi, Montanaro and Cioni2008; Vicari et al., Reference Vicari, Albertoni, Chilosi, Cipriani, Cioni and Bates2000). However, despite typically better recovery of children with TBI than of those who sustained the injury during adulthood, lingering cognitive impairment has been reported for children as well as adults recovering from TBIs (Code, Reference Code1999; Tavano et al., Reference Tavano, Galbiati, Recla, Formica, Giordano, Genitori and Strazzer2009). Here, as in reports of language impairment in multilingual speakers following a left-hemisphere stroke, questions can be asked about comparable versus differential impairments of the two or more languages and about the circumstances or variables that may contribute to nonparallel patterns.

In one of the few published studies on the course of language impairment following TBI in a bilingual child, Tavano et al. (Reference Tavano, Galbiati, Recla, Formica, Giordano, Genitori and Strazzer2009) reported on an Arabic-Italian bilingual who sustained left-sided brain injury at the age of 7 months. Testing at 8, 18, and 31 months revealed impaired cognitive abilities, such as memory and attention, and severe impairment of expressive and receptive language abilities. The impairment was similar in both his Italian, the language of the environment, and Arabic, the language spoken at home.

Another case was reported by Sebastian, Dalvi, and Obler (Reference Sebastian, Dalvi, Obler, Gitterman, Goral and Obler2012), highlighting the role of the writing system in rehabilitation from aphasia resulting from a TBI. The patient was a multilingual with proficiency in Marathi, English, and Hindi who sustained a TBI at age 16. Of interest here is the differential impairment evident in his expressive language skills, amid comparable abilities in his comprehension skills in both Marathi and English. Specifically, whereas both languages demonstrated impaired production, there was a differential effect of modality with better spoken language abilities in Marathi but better written ability in English. Treatment, provided bilingually 16 years postonset, was effective, resulting in a less-severe agrammatism in both languages. It is possible that language-specific differences between Marathi and English influenced the pattern of impairment manifestation in this participant, similar to differential language effects reported above for individuals with aphasia and dementia.

In one report on a multilingual adult who sustained TBI, Eng and Obler (Reference Eng and Obler2002) reported on a 65-year-old man, a Toisanese-Cantonese-English speaker who acquired dyslexia following a fall. His most notable impairment was his slow and error-prone reading, observed in both English and Cantonese. Upon testing, comparable patterns of errors (e.g., more errors on low-frequency words) were observed in both languages tested. Nevertheless, script-specific effects were also noted; for example, visual errors characterized his performance in English, whereas semantic errors were typical of his performance in Chinese. This dissociation is likely linked to orthography-specific effects, as it has been reported for languages that differ in their script systems (e.g., Eng & Obler, Reference Eng and Obler2002, for Chinese and English) but not for languages that share orthographic systems (e.g., Laganaro & Overton Venet, Reference Laganaro and Overton Venet2001, for Spanish and English).

Additional information about how language-specific characteristics affect impairment and recovery in multilinguals is warranted. The manifestation and recovery trajectory of the languages of multilingual speakers following TBIs is fertile ground for future research.