Determining language dominance in English–Mandarin bilinguals: Development of a self-report classification tool for clinical use

In multilingual Asian communities, determining language dominance for clinical assessment and intervention is often complex. The aim of this study was to develop a self-report classification tool for identifying the dominant language in English–Mandarin bilinguals. Participants (N = 168) completed a questionnaire on language history and single-word receptive vocabulary tests (Peabody Picture Vocabulary Test type) in both languages. The results of a discriminant analysis on the self-report data revealed a reliable three-way classification into English-dominant, Mandarin-dominant, and balanced bilinguals. The vocabulary scores supported these dominance classifications, whereas the more typical variables such as age of first exposure, years of formal instruction, and years of exposure exerted only a limited influence. The utility of this classification tool in clinical settings is discussed. A bilingual is anyone who can communicate in two languages by speaking, writing, listening, or reading, regardless of whether proficiency is nativelike. Bilinguals outnumber unilinguals worldwide (De Bot & Kroll, 2002); however, a simple © 2008 Cambridge University Press 0142-7164/08 $15.00 Applied Psycholinguistics 29:3 390 Lim et al.: Determining language dominance in bilinguals dichotomy may not be tenable in many Asian countries where English is often the lingua franca but family language is very important. For example, bilinguals in Singapore often acquire and use one language at home (Mandarin, Malay, or Tamil) but rely on English for education and subsequent employment. Even for early bilinguals, those who learn their family language and English simultaneously before the age of 6, one language is usually dominant. This kind of language history is widespread in Asia, and makes speech–language assessments complex. In particular, it raises the question of how much knowledge of a language is required before a person can be classified as a balanced bilingual, and treated accordingly. Even though bilinguals may be proficient in two languages, their competence may not be equivalent across domains (home vs. classroom/workplace; Grosjean, 1985). Moreover, language use and the nature of bilingualism often change across the lifespan if the acquisition of one language is interrupted and insufficient, or if the learning of one language is more structured and formal because it involves reading and writing as well as speaking and listening (Albert & Obler, 1978; Bialystok, McBride-Chang, & Luk, 2005; Hamers & Blanc, 2000). In fact, receptive bilingualism (understanding but not speaking/writing a parent’s language) is likely to be much more common than academic proficiency in any linguistic setting where the home language receives little emphasis in school (see Bialystok, 2007; De Houwer, 2007). The acquisition and maintenance of a bilingual’s two languages also depends on other interrelated factors such as language practice, language choice, and language attitudes (Hakuta & D’Andrea, 1992). Factors such as these, coupled with exposure to two cultures in many countries, influence bilingual children’s cognitive development (Kroll & De Groot, 1997) as well as their linguistic abilities and code mixing (Genesee, Paradis, & Crago, 2004). The complex patterns of language acquisition have made it hard to ascertain which language is the dominant one. Several methods for determining language dominance in bilinguals have been proposed (Flege, Mackay, & Piske, 2002; see also Grosjean, 1982). However, these have been designed mainly for migrant populations who use a native or first language (L1), and then acquire a second language (L2) after immigrating to the L2-speaking country as adults, usually after 15 years of age. This renders them unsuitable for establishing language dominance in multilingual multicultural countries such as Singapore, Malaysia, Taiwan, China, and India, where the distinction between L1 and L2 is less clearcut and varies from one family to another. To our knowledge, a classification system for language dominance in a multilingual Asian context has not been systematically investigated before, and hence, the focus of this methodological study. Language dominance is easily confused with language proficiency. Birdsong (2006b) suggests that dominance, in psycholinguistic terms, usually indicates a difference in processing ability between L1 and L2, whereas proficiency is viewed in terms of the mastery of syntax, vocabulary, and pronunciation of a language. Even though “levels of proficiency and degrees of dominance tend to correlate” (Birdsong, 2006b, p. 47), bilinguals can have almost nativelike proficiency in both languages but still consider one language to be better than the other. Alternatively, they may be dominant in one language (L1 or L2) but not necessarily be highly proficient in that language. Applied Psycholinguistics 29:3 391 Lim et al.: Determining language dominance in bilinguals Despite the considerable overlap between language dominance and language proficiency, for clinical practice it may be more relevant to measure dominance. For example, it has been previously suggested that the severity and type of stuttering behaviors may be different across a bilingual’s two languages, and that this may be influenced by language dominance (e.g., Howell et al., 2004; Jankelowitz & Bortz, 1996; Jayaram, 1983). Speech–language pathologists routinely work with a range of bilingual clients (e.g., Bernstein Ratner, 2004; Finn & Cordes, 1997). If language dominance affects the presentation of a speech or language disorder, SLPs may either underestimate or overestimate the overall severity of any disorder if they perform their assessments in one language only. Accordingly, it is important to determine which language (if any) is dominant to assess the nature of any disorder. It would also be essential to know whether therapy that is delivered in either the dominant or less dominant language yields better treatment outcomes. In determining language dominance, however, it is not clear which parameters are important in a particular setting. The array of parameters for late bilinguals (i.e., those acquiring L2 after 10 years of age; Perani et al., 1998) include age of acquisition (AoA) and age of first exposure (AoE), function and frequency of language use, the manner, environment, and years of language instruction and exposure, stability of language acquisition, age of arrival (AOA), and length of residence (LOR) in the L2-speaking country, language modes, and the level of language proficiency for understanding, speaking, reading, and writing (Flege et al., 2002; Grosjean, 1998; Langdon, Wiig, & Nielsen, 2005; Obler, Zatorre, Galloway, & Vaid, 2000). These variables frequently correlate with key theoretical concepts in L2 language processing and representation (Chen & Leung, 1989; Li, Sepanski, & Zhao, 2006), but they are not always meaningful as determiners of language dominance in early bilinguals. A priori, it may be reasonable to speculate that variables such as AoE, years of language instruction, and language exposure may not be good predictors of dominance for bilinguals in Asian countries such as Singapore, who are exposed to both languages before 5 years of age. Further parameters like AOA and LOR are not applicable to this bilingual population. Children in Singapore are usually exposed to at least two of the four official languages, English, Mandarin, Malay, and Tamil, in the home through local television and radio broadcasts and other public services (e.g., transport, shopping centers). Depending on their ethnic background, they are expected to become bilingual and literate in English (main medium of instruction) and in Mandarin, Malay, or Tamil during their primary education, which occurs from 6 to 12 years of age. This bilingualism continues through secondary education and into adulthood, but pupils vary considerably in their use and level of proficiency in each language. Even though the majority of Singaporeans function at the bilingual end of the Grosjean’s (2001) continuum, some may acquire balanced abilities in both languages, whereas others develop dominance in one language, or in particular modalities. For many bilingual Singaporeans, however, a common pattern is to use Mandarin for speaking but to read and write more in English. Whether AoE, years of formal instruction, and the number of years of language exposure, parameters that have been found to influence language proficiency and dominance in bilinguals from non-Asian settings, can effectively discriminate the dominant language in Applied Psycholinguistics 29:3 392 Lim et al.: Determining language dominance in bilinguals bilinguals in Singapore, or are associated with self-rated proficiency in all four language modalities has not been formally investigated. One might expect, for example, an inconsistent pattern in the relationship between the three parameters and the self-rated proficiency for individual language modalities because levels of proficiency may be modality specific. As a result of the unique language background of bilingual Singaporeans, variables such as the function, frequency, and environment of language use, and the level of language proficiency for all four language modalities may be more applicable to this bilingual population than other variables for determining language dominance. For studies that have relied exclusively on self-report, the selection and weighting of variables for deciding dominance in bilinguals who speak non-Asian languages varies considerably, and seem somewhat arbitrary. Cutler, Mehler, Norris, and Segui (1992) and Golato (2002) asked their French–English participants to state the language they would choose to keep if they were in a hypothetical situation where they could keep only one language. More conventionally, Altarriba (2003) classified her Spanish–English speakers as balanced bilinguals only when there were no significant differences in their self-reported ability to understand, write, and converse in the two languages. Tokowicz, Michael, and Kroll (2004) used a similar procedure for their Spanish–English bilinguals but then reassigned four participants to the L2-dominant group because they were living in an L2 environment. In addition to using single self-report measures to classify language dominance, other investigators have adopted a combination of two or more parameters including objective measures of proficiency. However, there is little agreement about how to combine measures, or how to interpret the scores from the different tests for the purpose of language dominance classification. In one of the five studies conducted by Flege et al. (2002), self-report and objective tests were used (selfratings of proficiency and a sentence repetition task) to divide participants into one of three groups: Italian dominant, English dominant, and balanced bilinguals. The resulting classifications were then compared with the data obtained for AOA, LOR, language use, and two other objective measures (sentence translation and strength of foreign accent). Self-rating ratios were calculated from the bilinguals’ ability to speak and understand Italian compared to English (verbal self-rating ratios), and read and write Italian compared to English (written self-rating ratios). Sentence duration ratios were also derived by dividing the mean duration of repeated English sentences (milliseconds) by that of Italian sentences. These three ratios were then ranked-ordered and averaged so that each bilingual received an average rank score. The authors then assigned equal numbers of bilinguals in each group: the 18 bilinguals with the highest and lowest ranks were classified Italian dominant and English dominant, respectively, whereas the remaining 18 were considered balanced bilinguals. Flege et al.’s (2002) rationale for dividing the 54 participants into equal-size groups is unclear, but their use of multiple measures for language dominance classification is commendable. The main problem is how to decide on the combination of tests to use for assessing dominance in Asian bilinguals. It is difficult to generate equivalent objective tests in different languages (Grosjean, 1998), and especially challenging when the two languages are structurally dissimilar. For Applied Psycholinguistics 29:3 393 Lim et al.: Determining language dominance in bilinguals example, English and Mandarin are sharply contrasted in terms of orthography, phonology, and morphology. There is also a range of objective assessments and little consensus about which is best: standardized or nonstandardized assessments of language ability (e.g., Bialystok & Miller, 1999; Jared & Kroll, 2001), scores from a standardized examination such as TOEFL (e.g., Golestania et al., 2006), and various laboratory tests of speed, fluency, and automaticity (e.g., Flege et al., 2002). Therefore, a more acceptable approach might be to first determine language dominance using self-report ratings (Langdon et al., 2005), and then use the results of objective tests to substantiate rather than as a determiner of language dominance (Grosjean, 1998). There is a growing body of research that shows that self-assessments of proficiency are valid and reliable measures of language skills, and are correlated highly with ratings by experienced judges and standardized test (Grosjean, 1982; Langdon et al., 2005; Oscarson, 1989). In a recent survey of 41 published studies in the bilingual or L2 literature, Li et al. (2006) showed that self-assessments in understanding, speaking, reading, and writing ability were among the 10 most frequently asked questions in language history questionnaires used in bilingual research. However, Grosjean (1982) argued that language dominance assessments should not only consist of proficiency measurements of bilingual’s ability to understand, speak, read, and write a language, but also include an examination of how a bilingual uses the two languages. In particular, he emphasized the need to consider the frequency and domain of language use. Frequency and domain of language use are important variables as they are related to language proficiency. Bilinguals commonly experience changes in their language environment, and so their needs for particular language skills will change accordingly, as will their proficiency in each language. Previous researchers have used self-report measures to determine language dominance, but prior to this study, none have used data from all three of the key variables: language proficiency, frequency of language use, and domain of language use. One complication that will arise whenever two or more measurements are employed is that the results derived from different tests do not always converge (e.g., Chincotta & Underwood, 1999; Jared & Kroll, 2001; Langdon et al., 2005). For example, Langdon et al. (2005) discovered that only 8 of the 25 bilinguals received the same bilingual group classification across their two objective assessments, word listing by domain (WLD) and the Alzheimer’s quick test: assessment of parietal function (AQT). A planned deliverable for this study was to develop a way of handling potentially conflicting classification results systematically by using a predetermined set of criteria. The use of objective tests as a means of validating self-report measures of language dominance may not be easily adopted in Asian countries such as Singapore where a perennial problem is the lack of culturally specific, standardized objective assessments. Therefore, an alternative method of validating our self-report tool was required. In their recent study, Li et al. (2006) used a discriminant analysis to show that their method of measuring overall L2 proficiency could correctly classify their bilingual participants into three L2 proficiency groups: low, medium, and high. This same statistical procedure would also be valuable for validating the accuracy of our self-report classification tool. Applied Psycholinguistics 29:3 394 Lim et al.: Determining language dominance in bilinguals To summarize, the main aim of this study was to develop systematic guidelines for interpreting a self-report classification tool comprising ratings of language proficiency, and frequency and domain of language usage. The tool was validated using a discriminate analysis and a simple measure of proficiency such as receptive vocabulary. The second aim was to explore the relationship between the three principal parameters referred to in the literature on bilinguals from nonAsian settings, AoE, years of formal instruction, and years of exposure, and their utility for distinguishing between bilinguals with different dominance patterns and proficiency self-ratings.