Missing the Mix: Perceiving Code-Switches as a Mechanism for Bilingual Adaptation

Abstract

Code-switching is a common and natural aspect of many bilingual individuals’ everyday language use. For many infants growing up in bilingual environments, such language mixing forms may be a regular part of their daily input. However, the frequency and type of code-switching can vary widely by caregivers’ language proficiency, context, and social norms. As early as infancy, increased exposure to code-switches in bilingual environments promotes differences in attention at the behavioral, physiological, and neural levels. In this article, we propose that exposure to code-switching may act as a mechanism driving cognitive adaptations in bilingual children’s attention, but more evidence is needed on children’s exposure to code-switching. Robust measures of bilingual experiences focusing on qualitative and quantitative aspects of code-switching are necessary to deepen our understanding of the variations in bilingual cognitive development.

A topic of scientific contention is whether bilingualism affords any cognitive benefits. For more than two decades, scientists have debated whether bilingual experiences cross the language domain and improve nonlinguistic cognitive abilities. In the early 20^th century, bilingualism was often viewed as a potential cause of cognitive delays or deficits; however, perceptions of bilingualism shifted in the late 20^th century when studies showed bilingual children excelling in executive function tasks (Bialystok, 1999; Peal & Lambert, 1962).¹ Most research on the bilingual cognitive advantage has focused on those who produce language, particularly adults and children older than 18 months (for meta-analyses, see Gunnerud et al., 2020; Lowe et al., 2021; Ware et al., 2020), with few studies examining what happens in infancy (see Singh, Barr et al., 2024). Indeed, theoretical frameworks of bilingual cognition are largely informed by evidence from adults (Abutalebi & Green, 2016; Green & Abutalebi, 2013) and frameworks adopting a lifespan perspective tend to focus on aging adults (Bak et al., 2014; Gallo et al., 2020; Grundy et al., 2017). Yet infants understand language much earlier than they begin producing words. The evidence from studies of infants highlights the importance of incorporating the period of early language acquisition and the social context of language during early development, particularly input from primary caregivers.

In this article, we examine child-directed code-switching as a unique bilingual experience that may shape cognition, particularly attentional abilities, in early childhood. First, we outline theoretical frameworks on the bilingual cognitive advantage, highlighting the limited evidence from early childhood and the broader multilingual context. We then turn to differences in perceptual abilities supporting bilingual language acquisition, and discuss how code-switching practices in bilingual homes may drive cognitive and neural adaptations in children. We conclude with recommendations for improving code-switching measurements, urge researchers to collect sources of code-switching use, and encourage the reporting of children’s sociodemographic and sociocultural factors.

Theoretical Perspectives of Bilingual Cognition

Switching between languages is a unique bilingual experience. Several theoretical accounts posit that the demands of language switching shape executive function—either by improving performance or by reorganizing neural systems—and that such changes may differ depending on individual variability (Bialystok, 2017; de Bruin, 2019; Green, 1998; Green & Abutalebi, 2013; Grundy et al., 2017; Luk & Bialystok, 2013). For example, the adaptive control hypothesis (Green & Abutalebi, 2013) outlines how different interactional contexts (e.g., single-language, dual-language, dense code-switching) engage different cognitive control processes (e.g., inhibition, monitoring). In dual-language contexts, speakers switch languages with different speakers or in distinct environments (e.g., home versus school). In contrast, dense code-switching contexts involve alternating languages within a single utterance, sometimes blending morphosyntactic elements from both (Green & Abutalebi, 2013). Other accounts, such as the inhibitory control model (Green, 1998) and the bilingual anterior to posterior and subcortical shift hypothesis (Grundy et al., 2017), further emphasize how language-switching practices engage inhibition and lead to neural changes at a later age (Pliatsikas, DeLuca, & Voits, 2020). Although these frameworks position language switching as central to bilingual cognitive adaptations, many empirical studies testing them may not directly measure switching frequency, limiting conclusions about how switching experience drives cognitive and neural differences.

Studies on bilingual cognition are further constrained by their quasi-experimental design, typically comparing monolingual and bilingual groups despite an increasing understanding that no two bilingual individuals share the same profile (de Bruin, 2019). Even when bilingualism is conceptualized on a spectrum, studies often rely on a narrow set of language measures. For infants and young children, these typically include proportion of exposure and vocabulary knowledge (Rocha-Hidalgo & Barr, 2022), whereas for older populations, they include age of acquisition, proficiency, and frequency (DeLuca et al., 2019; Surrain & Luk, 2019). While such metrics provide valuable insight into bilingual individuals’ knowledge and experience with each language, they offer limited insight into the practice of code-switching—a unique feature of bilingualism that underpins theories of bilingual cognition and the notion of a bilingual cognitive advantage.

It is important to distinguish between language switching and code-switching. Language switching generally refers to alternating between languages across conversations or speakers (i.e., dual-language context; Green & Abutalebi, 2013), whereas code-switching (also referred to as code-mixing and language mixing; Byers-Heinlein, 2013; Cedden et al., 2024) involves mixing languages within a single utterance (Myers-Scotton, 1993; Poplack, 2015; Yim, 2023). Speakers may engage in three types of code-switching: 1) inter-sentential: switching languages between sentences (e.g., “¡Mira eso! [Look at that!] It’s a doggie); 2) intra-sentential: switching languages within the same sentence (e.g., “Mira el [Look at the] doggie”); and 3) intra-word: blending morphemes from both languages (e.g., “troca” [truck with “a” suffix; actual Spanish word: camioneta; Myers-Scotton, 1993; Poplack, 2015).

Bilingual individuals’ code-switching experience varies by speaker and the speaker’s environment. Societal contexts (e.g., workplace, home) and linguistic factors (e.g., linguistic proximity, attitudes) contribute to the variability in a bilingual individual’s linguistic environment, extending their influence to their code-switching experience, both in exposure and production (see Table 1 for a summary of factors and their association with code-switching). For instance, many bilingual adults code-switch more frequently with their family and friends, but do so rarely at work (Dewaele & Wei, 2014), and bilingual individuals in multilingual communities often code-switch more than bilingual individuals in predominantly monolingual communities (Myers-Scotton, 1993, 2017; Poplack, 1980).

Table 1.

Factors Influencing Code-Switching in the Bilingual/Multilingual Environment

Sociocultural Influence	Factors	Description
Source of input/exposure (or interlocutor)	Parents	Primary caregivers, or guardians, whose language use, native language status, and home language strategy (e.g., one parent one language) influence bilingual children’s immediate language environment (Place & Hoff, 2011): Parents may implicitly use different types of code-switching (or refrain from using it) depending on their child’s age (Kremin et al., 2022)
	Siblings	An individual who shares one or two parents: Older siblings are a source of second language exposure in the home that supports younger bilingual children’s second, or heritage, language abilities (see Paradis, 2023). Twenty percent of parents reported their children code-switched between themselves (Barron-Hauwaert, 2011, Chapter 3).
	Friends	Individuals’ peers: Peers become a source of language exposure whose second language use can support a bilingual child’s second language maintenance (see Paradis, 2023). Multilingual adults code-switch more with friends and colleagues than with strangers and family members (Dewaele & Wei, 2014).
	School	Learning environment in which children spend the most time outside the home: The school environment (teachers, instruction, peers, extracurricular activities) becomes a rich source of language exposure and can promote dominant language acquisition and maintenance (see Paradis, 2023). The classroom setting establishes “acceptable” code-switching practices in school (Wei & Martin, 2009).
Language dominance (balance)	Age of acquisition	The age at which an individual begins learning, or is exposed to, a second language: Individuals may be simultaneous bilinguals (learning two languages at the same time) or sequential bilinguals (learning another language after acquiring a first; Gertken et al., 2014). Simultaneous bilinguals engage in code-switching more frequently than do sequential bilinguals (Myers-Scotton, 2017).
	Proficiency	The extent to which a bilingual speaker can understand, speak, write, and read in each language (Gertken et al., 2014): Multilingual adults with high proficiency across their languages reported higher code-switching use than did low-proficiency multilingual adults (Dewaele & Wei, 2014).
	Language experience	The setting (home, school, country) and the time individuals spent learning and being immersed in a language (Gertken et al., 2014): Multilingual adults who acquired their languages earlier used code-switching more (Dewaele & Wei, 2014).
	Language attitude	The speaker’s sense of self in relation to speaking the language and identifying with the culture associated with the language (Gertken et al., 2014): Attitudes toward code-switching, both at the community and the individual level, affect code-switching use (Dewaele & Wei, 2013; Olson, 2024).
	Language use	The amount of time, proportion of time, or frequency with which an individual uses (e.g., speaks, hears, reads, writes) each language in a given time frame (Gertken et al., 2014): American Spanish-English bilingual toddlers code-switched more if they had less exposure to Spanish (Smolak et al., 2020)
Language(s)	Status	A language’s social standing (e.g., official language, majority/minority status): People express social preferences for higher-status speech (Kinzler, 2021). Canadian French-English bilinguals rated English and French as of similar status while rating code-switching as of lower status (Rodrigo-Tamarit & Loureiro-Rodríguez, 2024).
	Proximity	The degree of relatedness between two languages (Schepens et al., 2013): Code-switches occur more often next to a cognate (words that share a similar root; Broersma, 2009).
Sociodemographic	Age	An individual’s chronological age: Older adults engage more in code-switching with friends and family than younger adults (Dewaele & Wei, 2014).
	Gender	An individual’s sense of their own gender: Women engage in code-switching more than men (Dewaele & Wei, 2014).
	Immigrant status	Individual’s immigrant status in their country of residence (e.g., citizen, resident): Immigrants’ duration of time in their country of residence should also be considered. First-generation immigrants may hold negative attitudes toward code-switching (Mata, 2002).
	Personality	Individuals’ personality traits (e.g., openness, conscientiousness, extraversion, agreeableness, neuroticism): Extroverted individuals report using code-switching with others more than do introverted individuals (Dewaele & Wei, 2014).
	Education	Individuals’ formal schooling (e.g., years in school, degree): Individuals with lower and higher levels of education report more favorable attitudes toward code-switching than individuals who hold bachelor’s degrees (Dewaele & Wei, 2013).
	Biculturalism	Individuals’ identity within two cultures: Bicultural adults, or those who identify with two cultures, report engaging in code-switching frequently (Yim & Clement, 2021).
	Ethnic/group identity	The (ethnic) group or community an individual belongs to: For example, code-switching patterns (e.g., pauses, motivation) reflect comfort and acceptance in engaging in code-switching practices (Myers-Scotton, 1993), evidenced by differences between individuals in Ottawa-Gatineau and Puerto Rican communities (Yim, 2023).
Language context	Single language	Language use is designated to separate contexts (Green & Abutalebi, 2013).
	Dual language	Both languages are used, but there are no switches within an utterance (Green & Abutalebi, 2013).
	Dense code-switching	Speakers frequently mix languages (e.g., insertion, switching) within an utterance (Green & Abutalebi, 2013).
Societal context	Classroom	The school environment, particularly the classroom, may be single language or dual language. Teachers may use code-switching to facilitate communication and student engagement in bilingual programs (Cahyani et al., 2016).
	Workplace	Where people work, often considered a formal setting: Bilingual adults report using code-switching less frequently at work than with friends; moreover, individuals who work in a multilingual setting report code-switching more at work than with family (Dewaele & Wei, 2014).
	Country	The influence of institutional language policies set by the government: For example, French and English are both official languages in Canada, resulting in support for bilingual education programs (Wright & Chan, 2019). Code-switching practices in the classroom may be discouraged based on institutional policies (Wei & Martin, 2009).

Code-switching practices and attitudes may be transmitted between generations. For example, in one study, Mexican-immigrant parents in the United States associated code-switching with a lack of language proficiency but endorsed its practice in their second-generation immigrant adult children (Mata, 2022). Communities that accept and hold positive code-switching attitudes may spur parents to use code-switching with their children, as is evident in Mexican American populations (Fought, 2010). In contrast, many Canadian English-French bilingual adults hold negative attitudes toward code-switching, which may discourage such practices (Rodrigo-Tamarit & Loureiro-Rodríguez, 2024). Indeed, in one study, Mexican American English-Spanish bilingual parents demonstrated higher rates of child-directed code-switching than did Canadian English-French bilingual parents (Bail et al., 2015; Kremin et al., 2022).

From birth, bilingual infants may be exposed to their caregivers’ code-switching practices in different ways. The impact of code-switching experiences on bilingual cognition may begin early in development, yet most research has focused on adults. Examining how bilingual infants process and learn language from code-switching input, and how often they hear code-switching, offers a unique opportunity to test and refine bilingual cognition theories at the onset of language acquisition.

Bilingual Language Acquisition in Infancy

At birth, infants use prosody (rhythm and intonation) to distinguish between familiar and unfamiliar languages of different rhythmical classes (Mehler et al., 1988; Nazzi et al., 1998). This early language discrimination ability helps infants attune to the acoustic and phonological cues in their language environment (Werker, 2018). In addition to auditory sensitivity, infants rely on audiovisual information to support language learning. Infants who focus on a speaker’s mouth distinguish similar-sounding phonemes (e.g., /t/ versus /d/) and words (e.g., path versus bath; Teinonen et al., 2008; Weatherhead & White, 2017). Infants raised in bilingual environments follow a language development trajectory similar to monolingual infants (Werker et al., 2009), but bilingual infants are especially attuned to audiovisual cues. In one study, compared to monolingual infants at 4, 8, and 12 months, Spanish-Catalan bilingual infants tended to focus on a speaker’s mouth earlier in development and for a longer period (Ayneto & Sebastián-Gallés, 2017; Pons et al., 2015). In other studies, second language learners increased their attention to the mouth, especially when navigating phonetically similar languages (Catalan and Spanish) and understanding complex speech (Birulés et al., 2019, 2020; Birulés, Bosch et al., 2024).

In the absence of sound, bilingual infants detect language switches by focusing on a speaker’s mouth. In a habituation study, researchers presented silent videos of speakers alternating between English and French to 4-, 6-, and 8-month-olds raised in monolingual English or bilingual English-French households (Weikum et al., 2007). Infants who detected a language switch looked longer at the speaker’s mouth. All 4- and 6-month-olds detected switches, but by 8 months, only bilingual infants retained this ability. Spanish-Catalan bilingual infants demonstrated the same sensitivity, despite no exposure to English or French, suggesting that this phenomenon reflects a general bilingual ability rather than language-specific experience (Sebastián-Gallés et al., 2012).

Nevertheless, recent findings suggest constraints on bilingual infants’ ability to detect language switches. In one study, bilingual Spanish-Catalan 4-month-olds detected audiovisual language switches between rhythmically distant languages (English and Catalan/Spanish), but could not do so when the switch occurred between two closely related languages (Catalan and Spanish; Birulés, Pons, & Bosch, 2024). Moreover, the infants required at least 10 seconds to detect the switch, underscoring the particular challenge of perceiving language switches in close-language contexts. However, parent-reported use of overall code-switching and infants’ ability to detect switches were not related. Taken together, this work highlights the key role of perceptual processes in bilingual language acquisition, while also pointing to the heightened demands imposed by code-switching in close-language bilingual environments and the need for investigating the nuances of different types of code-switching.

Code-Switching Practices in Bilingual Homes

Historically, code-switching was believed to reflect insufficient proficiency in both languages (Heredia & Altarriba, 2001), and parents were often encouraged to maintain languages separately (e.g., via the one-parent-one-language approach; Kohnert et al., 2005). Today, speech-language pathologists recognize code-switching as a natural practice (Kohnert et al., 2005). Evidence suggests that, on average, Spanish-English bilingual parents in the United States code-switch with their children about 16% of the time, though this varies widely, ranging from none to more than 25% of interactions (Bail et al., 2015). In Canada, French-English bilingual parents who code-switch used inter-sentential code-switching to provide immediate translations and support their children’s word learning (Byers-Heinlein, 2013; Kremin et al., 2022). In both cultural settings, code-switching was not constant; instead, child-directed code-switching tended to be used strategically to support comprehension.

Evidence on whether child-directed code-switching benefits or hinders children’s language development is mixed. For instance, in one study, Canadian bilingual parents who reported frequent code-switching behaviors had children with smaller receptive vocabularies (Byers-Heinlein, 2013). In contrast, in another study, which measured code-switching in Spanish-English-speaking U.S. Latinos during parent-child play sessions, intra-sentential code-switching was linked to larger conceptual and productive vocabularies (Bail et al., 2015). These discrepancies may reflect cultural differences, differences in measurement approaches, or the fact that the impact of child-directed code-switching may depend on children’s cognitive abilities. Indeed, evidence suggests that U.S. English-Spanish bilingual parents’ frequent code-switching supports receptive and expressive language in English-Spanish bilingual children with strong verbal working memory, but may hinder children with weaker verbal working memory (Kaushanskaya & Crespo, 2019). This relation is likely bidirectional, with children’s skills also shaping how parents code-switch, but more research is needed to clarify this dynamic in early development.

Bilingual Cognitive Adaptations in Infancy

Groundbreaking findings that bilingual children outperform monolingual children in nonlinguistic tasks assessing attention and inhibitory control (Bialystok, 1999; Carlson & Meltzoff, 2008; Tran et al., 2015, 2019) resulted in the bilingual adaptation hypothesis (Bialystok, 2017), which proposes that bilingual environments requiring frequent language switching enhance the functioning of cognitive mechanisms. Attention and inhibitory control are key cognitive mechanisms that support language processing, but researchers have identified differences in how bilingual individuals use them in typical communication (Blanco-Elorrieta & Pylkkänen, 2016). Inhibitory control is primarily engaged during language production, particularly when bilingual individuals switch languages and suppress the nontarget language (Green, 1998). In contrast, attention plays a larger role during language comprehension, especially when processing other speakers’ switches (Blanco-Elorrieta & Pylkkänen, 2016). However, not all people who are bilingual show these benefits (Gunnerud et al., 2020; Lowe et al., 2021; Ware et al., 2020). Despite the debate, theoretical questions, including how code-switching shapes cognitive outcomes, remain.

Infancy provides a unique developmental window for examining the early experiences that may shape cognitive changes. In one study, bilingual Italian 7-month-olds outperformed monolingual peers in a cognitive flexibility task, successfully adapting to post-switch rules (Kóvacs & Mehler, 2009). This finding was later replicated in a study of Canadian bilingual infants who oriented their gaze to the anticipated location more quickly than did monolingual infants (Comishen et al., 2019). These studies attributed the bilingual effect to enhanced inhibitory control. However, some scholars argue that inhibitory control may not be an appropriate explanatory mechanism since infants do not produce language (D’Souza & D’Souza, 2016, 2021). Further concerns have been raised about the small sizes of samples and the analytical methods in these studies. Indeed, more recent research has failed to replicate the earlier (Kovács & Mehler, 2009) results (Dal Ben et al., 2022; D’Souza et al., 2020; Kalashnikova et al., 2021; Spit et al., 2023). Findings from these studies that failed to replicate prior results, which we discuss later, point toward rapid shifting of attentional engagement and disengagement as a more likely adaptation in preverbal bilingual infants.

Attention—the ability to engage, disengage, and shift focus to sensory events (Posner, 2012)—is a consistent area of difference between bilingual and monolingual infants. Several studies have reported distinct attentional looking patterns in preverbal bilingual infants, though not necessarily superior performance. For example, in one study, bilingual Singaporean 6-month-olds dishabituated more quickly to repeated stimuli and fixated longer on novel ones (Singh et al., 2015). In another study, bilingual infants in the United Kingdom disengaged attention more rapidly, shifted gaze to new stimuli more quickly (D’Souza et al., 2020, Study 3), and switched gaze between two subtly different side-by-side images more frequently than monolingual infants (D’Souza et al., 2020, Study 4). Similarly, in a third study, Spanish-Basque bilingual infants shifted attention faster and fixated longer on visual rewards during a cognitive flexibility task than their monolingual peers (Kalashnikova et al., 2021). Extending this work, in a fourth study, Canadian bilingual infants exposed to more caregiver code-switching behaviors (measured via parent reports) shifted attention more rapidly to cues and targets presented on-screen, whereas infants exposed to less code-switching responded more slowly (Arredondo, Aslin, Zhang, & Werker, 2022).

Taken together, these results suggest that growing up in bilingual contexts may shape infants’ early attentional shifting. Exposure to code-switching behaviors, as proposed by theoretical frameworks of bilingual cognition (Bialystok, 2017; Green & Abutalebi, 2013), may be one contributing factor. However, only two studies (Arredondo, Aslin, Zhang, & Werker, 2022, and Arredondo, Aslin & Werker, 2022) have directly measured code-switching exposure in relation to attentional differences in bilingual individuals. Thus, it remains unclear whether attentional adaptations reported in other infant studies stem specifically from code-switching exposure or from broader aspects of the bilingual experience.

Cognitive and Neural Demands of Code-Switching

Bilingual adults often report that producing code-switches feels easy and natural (Yim & Clement, 2021; see also Zhu et al., 2022, for neuroimaging evidence). In contrast, processing code-switched speech can place additional demands on listeners (Blanco-Elorrieta & Pylkkänen, 2017; de Bruin et al., 2020). Like adults, English-French bilingual 20-month-olds and English-Spanish bilingual 7- to 11-year-olds showed delayed recognition when hearing code-switched sentences (Byers-Heinlein et al., 2017; Gross et al., 2019). Specifically, 20-month-olds demonstrated slower looking behavior and increased pupil dilation—a physiological marker of processing effort—when hearing intra-sentential code-switches (e.g., “Mira el [look at the] doggie!”; Byers-Heinlein et al., 2017).

In neuroimaging studies, bilingual adults showed increased activity in regions involved in cognitive control, specifically the left dorsolateral prefrontal cortex and anterior cingulate, when processing code-switched sentences (Blanco-Elorrieta & Pylkkänen, 2016, 2017; Rossi et al., 2021). These findings, along with delayed recognition of language switches, may indicate greater cognitive effort. More broadly, evidence on language processing suggests that when comprehension becomes difficult (e.g., due to ambiguity or noise), attention and cognitive control systems are recruited to resolve linguistic conflict and achieve comprehension (Novick et al., 2005, 2010). Specifically, regions associated with conflict resolution in both attention and language networks (i.e., the left frontal and temporal regions) are engaged when interpreting complex sentences (Novick et al., 2010). While code-switches are not inherently ambiguous, they may recruit these brain regions to manage the increased processing demands that are imposed.

A growing body of neuroimaging studies with bilingual adults and older children documents structural and functional adaptations in the brain (DeLuca et al., 2019, 2020; Gallo et al., 2020; Pliatsikas, DeLuca, & Voits, 2020; Pliatsikas, Meteyard et al., 2020). For example, in studies on attentional control, bilingual school-age children engaged left frontal regions more frequently than did monolingual peers, particularly among simultaneous bilingual individuals (those learning two languages at the same time; Arredondo et al., 2017; Arredondo, Kovelman et al., 2022; Costumero et al., 2015; Garbin et al., 2010; Mohades et al., 2014; Rodríguez-Pujadas et al., 2013, 2014). Only one study (Arredondo, Aslin, & Werker, 2022) has examined whether neural differences in attention among bilingual infants emerge during the first year of life, when infants are just beginning to recognize linguistic cues and words in their native language. In that study, Canadian bilingual infants’ left frontal activation during an attention task at 6 months correlated with parental code-switching reports, suggesting that attentional differences may be influenced by the cognitive demands associated with code-switching environments, though additional research with young children is needed to confirm this pattern. Specifically, young bilingual children regularly exposed to code-switching may show greater adaptations in attention behavior and neural processes.

Such findings would imply that bilingual infants in the earliest stages of language development experience greater cognitive demands and that early bilingual experiences lead to neuroplasticity changes before children even produce their first words. Therefore, variability in the multilingual environment can shape the brain’s functional organization from an early age, with adaptations likely driven by both the type and the frequency of code-switches. These findings underscore the importance of documenting the code-switching environments in which bilingual children develop to capture more accurately the variability in bilingual experiences from the start of development.

Looking Ahead

Currently, the field is shifting away from the notion of a bilingual advantage and toward a bilingual adaptation framework (Bialystok, 2024, 2025; D’Souza & D’Souza, 2021; Singh, Barr et al., 2024). This perspective emphasizes that, even in the absence of superior performance, bilingual individuals exhibit attentional patterns distinct from monolingual individuals, as well as neural changes shaped by the type of bilingual experience (DeLuca et al., 2019, 2020; Pliatsikas, DeLuca, & Voits, 2020). Researchers (Singh, Barr et al., 2024) recently proposed that the adaptations seen in bilingual infants’ attention may reflect generalized effects of environmental complexity and diversity, but they were not specific about the nature of these changes and did not specify code-switching as a possible mechanism. Here, we link evidence from infant studies to theoretical frameworks of bilingual cognition, and propose that early exposure to code-switching may guide adaptations in bilingual infants’ attentional processes.

Processing and comprehending code-switches is a uniquely complex bilingual experience. Yet most infant studies on bilingual cognition have measured only the amount of bilingual exposure (Rocha-Hidalgo & Barr, 2022), offering limited information about the types of multilingual experiences encountered by participants. Moreover, researchers need to report detailed sociodemographic information about children in their studies to understand the social and cultural contexts in which they are raised (Singh, Barakova et al., 2024). Race, ethnicity, socioeconomic status, and study location are often underreported in bilingual studies (see Supplemental Table 1), underscoring the need for standardized reporting practices (Singh, Barakova et al., 2024).

Studies also need to report families’ sociocultural and sociolinguistic contexts to ground researchers’ understanding of bilingual children’s code-switching environment. For example, researchers in one study (Kremin et al., 2022) contextualized the differences in their study’s child-directed code-switching frequency against those of another study (Bail et al., 2015) by acknowledging differences between U.S. Latino individuals and Canadian bilingual individuals in community attitudes to code-switching. Other contextual factors (e.g., immigrant status, conversational partners) are also important to consider; in Table 1, we describe sources of variability in code-switching experiences. Researchers must consider children’s larger language, social, and cultural backgrounds, and incorporate tools that capture more effectively the contexts of and attitudes toward code-switching.

Although surveys are the most convenient method for collecting data, they often fail to capture the richness of bilingual individuals’ code-switching experience, context, and proficiency (Cedden et al., 2024; de Bruin, 2019). Sociolinguists note that the lack of fine-grained code-switching analyses (e.g., language direction, type, setting) may limit researchers’ ability to assess connections between code-switching and cognitive functions (Cedden et al., 2024). In developmental research, the Language Mixing Scale (Byers-Heinlein, 2013) is the only instrument that captures parents’ child-directed code-switching practices by measuring frequency and types (e.g., intra-sentential, inter-sentential) while considering the direction of the language switch; more nuanced tools are needed. An ideal tool would capture the specific contexts in which code-switching occurs, parents’ code-switching proficiency and experience, and parents’ and communities’ attitudes toward code-switching. Researchers also need developmentally appropriate tools to track children’s own code-switching across time, including whether and when they understand or produce code-switches, what types they produce, and with whom.

To complement surveys, we recommend naturalistic observations to explore the role of child-directed code-switching environments. Audiotaping common interactions in children’s homes (e.g., during mealtimes, on weekend mornings, or at bedtime) could provide insight into when and how often children are exposed to code-switching. Qualitative analyses, grounded in established linguistic frameworks (e.g., the matrix language framework; Myers-Scotton, 1993), could then be applied to assess the quality of parental switches. The combination of qualitative and refined quantitative methods may help disentangle the mechanisms through which code-switching affects cognition.

Bilingual environments are inherently complex, and individual experiences vary widely across speakers and development. The field has begun to conceptualize bilingualism as a continuum of language knowledge and experience. However, the influence of broader social and cultural contexts on language use remains understudied. Systematically examining code-switching exposure, a language experience unique to bilingual individuals embedded within sociocultural contexts, can boost our understanding of why, and under what conditions, cognitive adaptations occur.

In conclusion, we propose that child-directed code-switching in early childhood plays a central role in shaping cognitive adaptations, particularly attentional processes, in children raised in multilingual environments. Bilingual adaptation cannot be understood by measuring language exposure alone; comprehension requires attention to the sociocultural and sociolinguistic contexts in which code-switching occurs. Parents’ use of code-switching is subject to sociocultural influences, and researchers need a nuanced and developmentally appropriate measure to capture variability across families and communities. Establishing such tools—and applying them alongside naturalistic and qualitative methods—offers a valuable opportunity to refine and extend current theoretical frameworks of bilingual cognitive adaptation.