Code-switching is a common phenomenon that bilinguals engage in, including bilingual children. While many researchers have analyzed code-switching behaviors to better understand more about the language processes in bilingual children, few have examined how code-switching behavior affects a child's linguistic competence. This study thus sought to examine the relationship between code-switching and linguistic competency in bilingual children. Fifty-five English–Mandarin bilingual children aged 5 to 6 years were observed during classroom activities over five days (three hours each day). A number of different word roots and mean length of utterance for both languages, and a number of code-switched utterances for each child, were computed. English receptive vocabulary scores were also obtained. Additionally, teachers rated children's English and Mandarin language competencies approximately six months later. Correlational and hierarchical regression analyses support the argument that code-switching does not indicate linguistic incompetence. Instead, bilingual children's code-switching strongly suggests that it is a marker of linguistic competence.
Code-switching is a common phenomenon that bilingual speakers regularly engage in. When bilinguals code-switch, words from two languages are used within a single discourse. In some studies, code-switching has been distinguished from code-mixing – code-mixing is defined as a practice of mixing languages in a single sentence while code-switching can occur either within or across sentence boundaries within a single discourse or constituent (e.g., Brice & Anderson, Reference Brice and Anderson 1999; Meisel, Reference Meisel 1989; Muysken, Reference Muysken 2000; Nicoladis & Genesee, Reference Nicoladis and Genesee 1997). In other studies, as well as the present study, code-switching and code-mixing are synonymously regarded as an alternation of two languages within the same speech act (Bokamba, Reference Bokamba 1989; Clyne, Reference Clyne 1987; Genesee, Reference Genesee 1989; Genesee, Paradis & Crago, Reference Genesee, Paradis and Crago 2004; Poplack, Reference Poplack, Smelser and Baltes 2001).
Code-switching has been well studied in bilingual adults, particularly with regard to the grammatical and communicative functions of the behavior (e.g., Cantone, Reference Cantone 2007; Gumperz, Reference Gumperz and Dil 1971; MacSwan, Reference MacSwan 2014; MacSwan & McAlister, Reference MacSwan and McAlister 2010; McClure, Reference McClure 1977; Poplack, Reference Poplack 1980). The complexity of bilingual adults’ code-switching generally reveals a sophisticated knowledge of the grammars of both languages and reflects the adults’ competency in using them appropriately. However, there has been much debate with respect to what children's code-switching behavior suggests about their linguistic competency.
Early studies on children's language alternation behaviors postulated that bilingual children mix or switch languages because 1) they are confused or 2) they are linguistically incompetent. According to proponents of the position that bilingual children mix languages because they are confused and cannot differentiate between the two languages (e.g., the Unitary Language System Hypothesis in young children aged 3 years and below; Genesee, Reference Genesee 1989), the lexicons and grammars of both languages in young bilingual children first exist in one single system, and only gradually develop into two separate linguistic systems by a process of language differentiation. In this framework, young bilingual children's mixing of two different language elements within the same utterance was seen as evidence of the pre-separation stage and, thus, was argued to be a reflection of their inability to differentiate two language systems (Köppe & Meisel, Reference Köppe and Meisel 1995; Redlinger & Park, Reference Redlinger and Park 1980; Volterra & Taeschner, Reference Volterra and Taeschner 1978). For example, Redlinger and Park ( Reference Redlinger and Park 1980) studied four 2-year-old bilingual children over five to nine months and suggested that the children experienced various stages of language differentiation. The children would start off with high rates of language mixing as they do not separate their two language systems. The high language mixing rates would then gradually decline as these children move from an undifferentiated single language system to two distinct language systems. Proponents of this position argued that the decrease in the language-mixing rate is, therefore, positively related to language development, at least for children aged 3 years and below.
Other researchers claimed that bilingual children code-switch not because they cannot differentiate the two language systems, but because they lack the lexical, grammatical and/or pragmatic competence in one or both of the languages known. Several studies have found that bilingual children aged between 2 to 6 years code-switch in order to fill in their lexical gaps – they tend to insert words from one language into another language when they do not have the translation equivalents (e.g., Deuchar & Quay, Reference Deuchar and Quay 2000; Cantone, Reference Cantone 2007; Lindholm & Padilla, Reference Lindholm and Padilla 1978; see Nicoladis & Genesee, Reference Nicoladis and Genesee 1997, for a review). Further, Bernardini and Schlyter ( Reference Bernardini and Schlyter 2004), who examined code-mixing patterns of five Swedish–French/Italian children aged 2 to 4 years, posited that children code-switch because they are not yet competent in structuring grammatical sentences in their “weaker” language. In addition, Vihman ( Reference Vihman 1985) suggested that a young bilingual child aged 3 years old or younger would not be focused on the situational context when developing a dual lexicon. As such, the child may code-switch inappropriately during this period, reflecting the absence of pragmatic competence.
Recent studies, however, have provided more complex and contradictory evidence. First, many studies have failed to confirm the Unitary Language System Hypothesis. Results suggest that young bilingual children are able to differentiate their two language systems from an early age and their code-switched utterances are systematic and conform to the grammatical constraints of each known language (e.g., MacSwan, Reference MacSwan 1999; Meisel, Reference Meisel 1994; Nicoladis & Genesee, Reference Nicoladis and Genesee 1997; Paradis, Nicoladis & Genesee, Reference Paradis, Nicoladis and Genesee 2000; van Gelderen & MacSwan, Reference van Gelderen and MacSwan 2008). Genesee ( Reference Genesee 1989) argued that, contrary to the Unitary Language System Hypothesis, young bilingual children are able to use their developing language systems differentially in contextually sensitive ways. Second, case studies have found that children's code-switching behavior illustrates a good understanding of the grammatical systems of both languages. For example, 2- to 4-year-old French–English bilingual children displayed code-switching patterns that were largely similar to that of their adult counterparts – grammatical constraints were adhered to in mixing patterns that involved sentential negation and pronominal subjects (Paradis et al., Reference Paradis, Nicoladis and Genesee 2000). Siri's data in Lanza ( Reference Lanza 1992) indicated that the two-year-old did not use the inflections of both languages interchangeably. English grammatical morphemes were only used with English lexical morphemes, such as “looks”, but Norwegian grammatical morphemes were used with both Norwegian and English words, such as “looker” and “husk er”. Results from Cantone ( Reference Cantone 2007) also revealed how all instances of Italian–German code-switching in 2- to 5-year-old children in her corpus were grammatical. Furthermore, an English–Spanish bilingual child, M, exhibited language-specific syntax and morphology in both her pure and mixed utterances before the age of 3 years (Deuchar & Quay, Reference Deuchar and Quay 1998). Therefore, the results of studies such as the aforementioned suggest that bilingual children's code-switching behavior does not indicate an inability to differentiate their two language systems or a lack of linguistic competency. Instead, they strongly suggest that children's code-switching behavior illustrates that they possess adequate grammatical knowledge of both languages.
Additionally, numerous studies have demonstrated that bilingual children are pragmatically competent and can code-switch according to the situation and interlocutor (e.g., Genesee, Boivin & Nicoladis, Reference Genesee, Boivin and Nicoladis 1996). Even though bilingual children below the age of 4 years have more single-noun insertions in their mixed utterances, these utterances reflect their awareness of social norms (De Houwer, Reference De Houwer, Kroll and de Groot 2005). For example, Siri code-switched in bilingual contexts but not in monolingual contexts, thereby reflecting her sensitivity to the social demands of the conversation (Lanza, Reference Lanza 1992). Two-year-old bilingual children were also able to adjust their rates of code-switching according to that of their interlocutors (Comeau, Genesee & Lapaquette, Reference Comeau, Genesee and Lapaquette 2003), suggesting that they are sensitive to the language choices of their interlocutors. Bilingual children's code-switched utterances were also found to be in accordance with the language socialization practices in their families. Chung ( Reference Chung 2006) found that a 4.5-year-old and an 11-year-old Korean-American (who were regularly exposed to both Korean and English before age 3) switched between the two languages when conversing with their family members who had different language preferences. This facilitated communication and comprehension between the family members despite these different preferences. Moreover, Vu, Bailey and Howes ( Reference Vu, Bailey and Howes 2010) found that 4.5- to 5.5-year-old Spanish–English bilingual children code-switched in their attempts to draw the interviewer's attention or to change speaking roles. These studies show that bilingual children have the pragmatic competence to adjust their code-switching behavior appropriately depending on the situational contexts.
Some researchers have attempted to examine the code-switching-linguistic-competency relationship through investigating whether code-switching in elicited narratives can be a marker of language impairment (LI). Iluz-Cohen and Walters ( Reference Iluz-Cohen and Walters 2012) found that 5- and 6-year-old Hebrew–English bilingual children with LI code-switched more than bilingual children with typical language development (TLD). Using the Bilingual English–Spanish Oral Screener (BESOS), Greene, Peña, and Badore ( Reference Greene, Peña and Bedore 2012) found that 5-year-old children's risk status for language impairment affected their code-mixing frequency. With the English screener, children who were identified as at-risk of LI code-switched more than the no-risk group. Interestingly, the no-risk group code-switched more on the Spanish screener than the at-risk group. The authors cited limited awareness of the social interaction and challenges in suppressing the irrelevant language as possible explanations for these findings. Contrary to these findings, Gutiérrez-Clellen, Simon-Cereijido and Erickson Leone ( Reference Gutiérrez-Clellen, Simon-Cereijido and Erickson Leone 2009) did not find any differences in the use of code-switching between 5- to 6-year-old bilingual children with LI and those with TLD. Clearly, the inconsistent findings across studies call for more research to be conducted in these areas.
Thus, despite earlier attempts to understand the nature of bilingual children's code-switching, the relationship between children's code-switching and linguistic competency remains not well understood, or at best, controversial (Baetens Beardsmore, Reference Baetens Beardsmore, Gopinathan, Kam, Pakir and Saravanan 1998; Kamwangamalu & Leng, Reference Kamwangamalu and Lee 1991; Ong & Zhang, Reference Ong and Zhang 2010). Furthermore, no study has investigated children's code-switching behavior in bilingual preschool settings, especially for children who spend a significant amount of their awake time at these centers, and at a time when their language skills are becoming more complex. Most research on children's code-switching behavior consists of case studies of parent-child interactions or is based on children's narrative samples in a laboratory setting. Information on groups of children's code-switching behavior in a larger natural language environment would be relevant and important to understand the effects of code-switching on bilingual children's language development. Many children spend approximately 10 hours a day or more away from home, such as in childcare or daycare centers. Their language development is, thus, largely influenced by their interactions in this larger and more complex environment (Chung, Reference Chung 2006; Comeau et al., Reference Comeau, Genesee and Lapaquette 2003; Nicoladis & Genesee, Reference Nicoladis and Genesee 1997). In short, code-switching in such sociolinguistic contexts has not yet been adequately examined. The present study, therefore, seeks to fill these gaps by investigating the relationship between children's code-switching and linguistic competency in preschool settings and adopting a quantitative approach toward the analysis of children's language behavior. Measures of 55 English–Mandarin children's spontaneous speech were obtained through five 3-hour observation sessions in two childcare centers. Information on the children's receptive vocabulary was also obtained. In addition, teachers’ assessments of the children's language competency in English and Mandarin were collected approximately six months after the observation sessions in order to ascertain whether any predictive relationship exists between code-switching and linguistic competency.
Fifty-five English–Mandarin bilingual children aged between 5;5 to 6;7 (M = 6.06, SD = 0.34) from two private childcare centers in Singapore Footnote 1 (33 from Center 1 and 22 from Center 2; 25 females, 30 males) were observed during their classroom activities. Four additional participants were excluded either because they had very low attendance during the observation days that resulted in very little recording time (less than 5% of the total recording time in the center) or because he or she spoke fewer than ten utterances throughout the entire observation session. Both childcare centers conducted classroom activities in English and Mandarin Footnote 2 .
Parents completed a demographic and language background questionnaire prior to the observation session. The questionnaire asked about the age and gender of the child, the language first acquired by the child, and the amount of time (in percentage) their child hears or speaks a language in a typical week (see Yow & Markman, Reference Yow and Markman 2016). The average amount of English and Mandarin exposure children had at home as reported by the parents was 55.30% (SD = 19.93%) and 41.80% (SD = 20.15%) respectively. All children were reported as simultaneous bilinguals (i.e., acquiring two languages at age 3 or younger), except for one who was reported as a sequential bilingual. Preliminary analysis found that including the single sequential bilingual child did not change the results significantly, thus all children were included in the final analyses. In addition, parents reported their highest education level as a measure of socioeconomic status (SES), ranging from 0 (no formal education) to 5 (postgraduate degree). The average parental highest education level was 3.98 (SD = 0.54).
Parents were informed about the study and were requested to complete the language background questionnaires that were distributed with the teacher-parent communication book. The observation was conducted for about three hours each day across five different days in each childcare center. We were thus able to record children's conversations in different settings throughout the week, such as during meal times, craft sessions, and free play. Teachers split children from their respective childcare center into two groups of 2 to 6 as part of their normal preschool routine. Two research assistants each followed and recorded one group of children with a video camera that also had an audio recorder attached to it throughout the recording duration. The research assistants held the camera and audio recorder as close to the children as possible without interrupting their activities. As the audio and video recording were meant to be as naturalistic as possible, there was no form of intervention from the researchers during the entire recording duration. The video recordings were transcribed and crosschecked with the audio recordings, especially when the conversations were unclear from the video recordings. After the observation sessions ended, children were tested individually on their receptive vocabulary using the Peabody Picture Vocabulary Test (4 th Edition; PPVT-IV; Dunn & Dunn, Reference Dunn and Dunn 2007). The respective teachers were asked to complete a short questionnaire on the language competency of those children who participated in the study approximately six months after the observation sessions ended (see section on Materials).
The Peabody Picture Vocabulary Test (4 th Edition; PPVT-IV; Dunn & Dunn, Reference Dunn and Dunn 2007) was administered individually to assess children's receptive English vocabulary. Each child was instructed to point to one of four pictures that depicted the word spoken by the experimenter. Eleven children from Center 1 and five children from Center 2 did not complete the PPVT. Raw scores were converted to age-based standard scores according to the manual. The average standardized score was 100.69 (SD = 12.33). As there is currently no equivalent approved version in Mandarin, the same task was not conducted in Mandarin.
Teachers were asked to rate the students’ expressive and receptive language competencies from 1 (very poor) to 5 (very good) approximately six months after the observation session ended. This questionnaire consisted of eight items (Table A1), which we developed based on the Language and Literacy section of the curriculum framework for kindergartens in Singapore (Singapore Ministry of Education, 2012). Examples include “he or she talks about drawings and artworks he or she has created” (expressive) and “he or she understands a good variety of words” (receptive). English teachers assessed English language competency while Mandarin teachers assessed Mandarin language competency of the respective children in their charge. The average teacher's rating of English and Mandarin competency was 3.75 (SD = 0.95) and 3.85 (SD = 0.79) respectively.
Children's utterances during the observation sessions were transcribed in accordance with CHAT and the transcriptions were analyzed using CLAN (MacWhinney, Reference MacWhinney 2000). Four additional research assistants, who were also native language speakers of English and Mandarin, were involved in the transcription and checking process. All videos were divided among the six research assistants. The research assistants independently transcribed the videos assigned to them. In accordance with the transcription and reliability checking methods detailed in Lust and Blume ( Reference Lust and Blume 2016), a different research assistant (i.e., second transcriber) checked through each transcription for errors or missing data. All transcriptions were checked sentence by sentence by crosschecking the video and audio recordings. When there were discrepancies, the second transcriber would discuss them with the first transcriber before making changes to the transcriptions. A third transcriber was involved if the first two transcribers could not come to an agreement.
In all transcriptions, onomatopoeia (imitation of sounds, e.g., “woof woof”) and ambiguous communicators that can be used in either English or Mandarin, such as “uh”/“哦”, “ah”/“啊”, “oh”/“噢”, Singlish Footnote 3 particles (e.g., “meh”, “la”, “na”, see Rubdy, Reference Rubdy 2007) were marked as non-words and thus automatically excluded from all analyses. Words that were not English or Mandarin were also marked as non-words (e.g., “chaota”, a Hokkien word which means burnt). All forms of routinized speech, such as standardized greetings before meal, text or nursery-rhyme reading, and games with standard lyrics (e.g., “scissors paper stone”) were excluded from the analyses as well. The basic unit of our analyses is an utterance, which is defined as “a word or group of words with a single intonation contour” (Lanza, Reference Lanza 1992, p. 638). A pure utterance (either in English or Mandarin) consists of words only in one language, and excludes single proper nouns, intra-sentential switches, and utterances that contain translations and imitations of other languages.
Lemma or word roots have often been used as a measure of children's lexical development (Hewitt, Hammer, Yont & Tomblin, Reference Hewitt, Hammer, Yont and Tomblin 2005; Thordardottir, Reference Thordardottir 2005; Watkins, Kelly, Harbers & Hollis, Reference Watkins, Kelly, Harbers and Hollis 1995). We computed this measure separately in English and Mandarin from the transcription data. For English, different words originating from the same word root (e.g., ‘eat-ate-eaten’) were considered as a single word root. NDWR was divided by the recording duration of each individual child because the recording duration varied from child to child (see Aukrust & Rydland, Reference Aukrust and Rydland 2011). Proper nouns (e.g., “Tangled”–the title of an English movie, “小兔跳楼” (xiao3tu4tiao4lou2)–the name of a local hand game) and unintelligible words were excluded from the computation of this measure.
Mean length of utterances (MLU) for English and Mandarin were calculated from the transcription data based on the guidelines provided in CHAT and CLAN (MacWhinney, Reference MacWhinney 2000). MLU, the ratio of morphemes over utterances (Brown, Reference Brown 1973), is frequently used as a measure of sentence complexity (Klee, Stokes, Wong, Fletcher & Gavin, Reference Klee, Stokes, Wong, Fletcher and Gavin 2004; Mishina-Mori, Reference Mishina-Mori 2011; Thordardottir, Reference Thordardottir 2005). Some researchers have noted that MLU is only meaningful until approximately 4 to 5 morphemes (Bernstein & Tiegerman-Farber, Reference Bernstein and Tiegerman-Farber 1997), while others have claimed that MLU is a valid measure even into the grade school years (Jones, Weismer & Schumacher, 2000; Miller, Frieberg, Rolland & Reves, Reference Miller, Frieberg, Rolland and Reves 1992). As there is currently no consensus on the age limit and morpheme-count limit of MLU (the mean MLUs in our study fall in the range of 4 to 5 morphemes: MeanEnglish MLU = 5.07; MeanMandarin MLU = 4.26), we proceeded to calculate both English and Mandarin MLU for our study and analyses.
Utterances included in the computation of MLU were those that only consisted of English or Mandarin words (i.e., pure utterances in English and Mandarin). Utterances with unintelligible words were included in the analysis, but the unintelligible words were excluded from the morpheme count. This approach was employed because noise from the environment decreased the intelligibility of many words (see Thordardottir, Reference Thordardottir 2005); both childcare centers had open classrooms and thus, voices of children in other groups or classrooms sometimes interfered with the recordings.
We coded two types of code-switching from the children's utterances: intra-sentential switches and inter-sentential switches (see Table 1). The total amount of code-switched utterances was the sum of both types of code-switching. The percentage of the total number of code-switched utterances made by each child was obtained by dividing the total number of code-switched utterances by the total number of utterances spoken by each child.
Table 1. Types and Examples of Code-switching.
A total duration of 21:16:43 hours and 30:09:48 hours of observation in Center 1 and Center 2, respectively, was transcribed and analyzed. An average of 648.78 utterances per child was recorded (SD = 542.37; see Table 2). The number of observed switches (intra-sentential and inter-sentential switches) in our sample of children constituted a small percentage of their total utterances (M = 8.95%, SD = 9.60, range = .23% to 33.83%.). There was no child who did not code-switch at all. Of the code-switched utterances, children engaged in similar amounts of intra-sentential switches and inter-sentential switches (M = 4.46% and 4.48% respectively). Children also produced a greater number of pure English utterances than pure Mandarin utterances and code-switch utterances (M = 77.01% vs. 16.57% and 8.95%, respectively), and a greater amount of English NDWR per minute and MLU than Mandarin NDWR per minute and MLU (M = 1.87 and 5.07 vs. .88 and 4.26), reflecting the population's dominance in English language. Preliminary analysis showed that both types of code-switched utterances (i.e., intrasentential and intersentential switches) did not differ in their relationship with the other measures of language competency, hence they were combined as the total number of code-switched utterances in subsequent analyses. Children varied in how much they spoke during the observation period, so the total number of code-switched utterances is divided by the total number of utterances to obtain a percentage of code-switched utterances for each child. In addition, we observed that the teachers themselves did not code-switch when they interacted with the children. The teachers also did not explicitly encourage or discourage code-switching from the children, although they made efforts to speak in only one language to the children.
Table 2. Measures of Children's Spontaneous Speech.
Note: The total number of all utterances is the sum of intra-sentential switch utterances, pure English utterances, pure Mandarin utterances, and other utterances such as single proper nouns, translation, and imitation. Inter-sentential switch utterances comprise only pure utterances.
As some of the measures of interest were not normally distributed, Spearman correlations were used. Partial correlations, controlled for age, between the various measures of language competency and percentage of code-switched utterances were conducted (Table 3). No significant correlations between measures of English competency (MLU of pure English utterances, English NDWR per minute, and English PPVT) and percentage of code-switched utterances were found. Thus, the amount of code-switched utterances was not significantly related to both the expressive and receptive measures of English competency. On the other hand, correlations between measures of Mandarin competency (MLU of pure Mandarin utterances, and Mandarin NDWR per minute) and percentage of code-switched utterances were positive and significant, r = .72 and r = .91, respectively, ps < .001, indicating that children who code-switched more also produced Mandarin sentences that are more complex and consist of a larger variety of words than children who code-switched less.
Table 3. Spearman Partial Correlations between Measures of Language Competency and Percentage of Code-Switched Utterances (controlled for age).
*Bonferroni corrected p value = .003