Mixed-Language Input and Infant Volubility: Friend or Foe?

Language mixing is a common feature of many bilingually-raised children's input. Yet how it is related to their language development remains an open question. The current study investigated mixed-language input indexed by observed (30-second segment) counts and proportions in day-long recordings as well as parent-reported scores, in relation to infant vocal activeness (i.e., volubility) when infants were 10 and 18 months old. Results suggested infants who received a higher score or proportion of mixed input in one-on-one social contexts were less voluble. However, within contexts involving language mixing, infants who heard more words were also the ones who produced more vocalizations. These divergent associations between mixed input and infant vocal development point for a need to better understand the causal factors that drive these associations.

Executive function skills account for a bilingual advantage in English novel word learning among low-income preschoolers

The current study compared economically disadvantaged bilingual and monolingual preschoolers' performance on an English novel word learning task and examined whether children's executive function (EF) skills account for differences in novel word learning performance across groups. In total, 39 English monolinguals and 35 Spanish-English bilingual preschoolers from low-income homes completed a battery of EF measures and the Quick Interactive Language Screener to gauge English novel word learning ability. Within a poverty context, bilingual preschoolers performed significantly better on measures of English novel word learning as compared with their monolingual peers. This bilingual advantage in novel word learning ability was mediated by short-term memory, but not inhibition or attention shifting, which indicates that gains in short-term memory may facilitate word learning in English for bilingual preschoolers from economically disadvantaged backgrounds. These findings have important practical implications for interventions designed to promote English vocabulary growth for low-income bilingual children.

Gesture development in infancy: Effects of gender but not bilingualism

Gesture is an important communication tool that provides insight into infants' early language and cognitive development and predicts later language skills. While bilingual school-age children have been reported to gesture more than monolinguals, there is a lack of research examining gesture use in infants exposed to more than one language. In this preregistered study, we compared three groups of 14-month-old infants (N = 150) learning French and/or English: bilinguals (hearing a second language at least 25% of the time), exposed (hearing a second language 10%-24% of the time), and monolinguals (hearing one language 90% of the time or more). Parent-reported use of communicative gestures was gathered from the MacArthur-Bates Communicative Development Inventories (CDI). Results showed that the three language groups had similarly sized gesture repertoires, suggesting that language exposure did not affect gesture development at this age. However, a gender effect was found, where girls produced more types of gestures than boys. Overall, these results suggest that gender, but not language exposure, contributes to differences in gesture development in infancy.

Associations between Bilingualism and Memory Generalization During Infancy: Does Socioeconomic Status Matter?

Past studies have reported memory differences between monolingual and bilingual infants (Brito & Barr, 2012; Singh et al., 2015). A common critique within the bilingualism literature is the absence of socioeconomic indicators and/or a lack of socioeconomic diversity among participants. Previous research has demonstrated robust bilingual differences in memory generalization from 6- to 24-months of age. The goal of the current study was to examine if these findings would replicate in a sample of 18-month-old monolingual and bilingual infants from a range of socioeconomic backgrounds (N = 92). Results indicate no differences between language groups on working memory or cued recall, but significant differences for memory generalization, with bilingual infants outperforming monolingual infants regardless of socioeconomic status (SES). These findings replicate and extend results from past studies (Brito & Barr, 2012; Brito, Sebastián-Gallés, & Barr, 2015) and suggest possible differential learning patterns dependent on linguistic experience.

A multi-lab study of bilingual infants: Exploring the preference for infant-directed speech

From the earliest months of life, infants prefer listening to and learn better from infant-directed speech (IDS) than adult-directed speech (ADS). Yet, IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multi-site study used the diversity of bilingual infant experiences to explore the impact of different types of linguistic experience on infants' IDS preference. As part of the multi-lab ManyBabies 1 project, we compared lab-matched samples of 333 bilingual and 385 monolingual infants' preference for North-American English IDS (cf. ManyBabies Consortium, 2020: ManyBabies 1), tested in 17 labs in 7 countries. Those infants were tested in two age groups: 6-9 months (the younger sample) and 12-15 months (the older sample). We found that bilingual and monolingual infants both preferred IDS to ADS, and did not differ in terms of the overall magnitude of this preference. However, amongst bilingual infants who were acquiring North-American English (NAE) as a native language, greater exposure to NAE was associated with a stronger IDS preference, extending the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes a similar contribution to monolingual and bilingual development, and that infants are exquisitely sensitive to the nature and frequency of different types of language input in their early environments.

Sensitivity to race in language comprehension in monolingual and bilingual infants

Past studies suggest that monolingual and bilingual infants respond differently to race information in face discrimination and social learning tasks. In particular, bilingual infants have been shown to respond more similarly to own- and other-race individuals, in contrast to monolingual infants, who respond preferentially to own-race individuals. In the current study, we investigated monolingual and bilingual sensitivity to speaker race in spoken word recognition. Two-year-old infants were presented with spoken words in association with visual targets. Words were presented in association with own- or other-race actors and were either correctly pronounced or mispronounced. Measuring speech-responsive eye movements to visual targets, we analyzed fixation to visual targets for correct and mispronounced words in relation to speaker race for each group. When presented with own-race speakers, both monolingual and bilingual infants associated correctly pronounced labels, but not mispronounced labels, with visual targets. When presented with other-race speakers, bilingual infants responded similarly. In contrast, monolingual infants did not fixate visual targets regardless of whether words were correctly pronounced or mispronounced by an other-race speaker. Results are discussed in terms of the sensitivities of bilingual and monolingual infants to novelty, learned associations between race and language, and prior social experiences.

Continuous developmental change explains discontinuities in word learning

Cognitive development is often characterized in terms of discontinuities, but these discontinuities can sometimes be apparent rather than actual and can arise from continuous developmental change. To explore this idea, we use as a case study the finding by Stager and Werker (1997) that children's early ability to distinguish similar sounds does not automatically translate into word learning skills. Early explanations proposed that children may not be able to encode subtle phonetic contrasts when learning novel word meanings, thus suggesting a discontinuous/stage-like pattern of development. However, later work has revealed (e.g., through using more precise testing methods) that children do encode such contrasts, thus favoring a continuous pattern of development. Here, we propose a probabilistic model that represents word knowledge in a graded fashion and characterizes developmental change as improvement in the precision of this graded knowledge. Our model explained previous findings in the literature and provided a new prediction - the referents' visual similarity modulates word learning accuracy. The models' predictions were corroborated by human data collected from both preschool children and adults. The broader impact of this work is to show that computational models, such as ours, can help us explore the extent to which episodes of cognitive development that are typically thought of as discontinuities may emerge from simpler, continuous mechanisms.

The effects of dual language exposure on executive function in Spanish-English bilingual children with different language abilities

The current study examined the effects of dual language exposure on executive function in 5- to 11-year-old Spanish-English bilingual children with different language skills. Dual language exposure was measured via parent report and was operationalized as the proportion of time spent in an environment where both English and Spanish were present. Executive function was measured via the Dimensional Change Card Sort (DCCS) task. Shifting costs, switching costs, and mixing costs were derived to index executive function performance. A significant interaction between extent of dual language exposure and language skills was observed such that children showed smaller shifting and mixing costs with increased dual language input as their language skills increased. The results suggest a graded effect of dual language exposure on executive function, where a robust language system may be required for dual language exposure to influence executive function.

Novel Word Learning in Children Who Are Bilingual: Comparison to Monolingual Peers

Purpose We compared novel word learning in 2nd-grade children with typical development who were Spanish-English bilinguals to English monolinguals to understand word learning in bilingual children. Method Children (monolinguals n = 167, bilinguals n = 76) engaged in 5 computer-based tasks that assessed word learning in 6 different contexts. The tasks measured children's ability to link novel names with novel objects/actions, make decisions about the accuracy of those names and objects/actions, recognize the semantic features of the objects/actions, and produce the novel names. For analysis, we used Bayesian repeated-measures analyses of covariance with Bayesian independent-samples t tests to clarify interactions. Results Monolingual and bilingual children differed in some, but not most, word learning situations. There was at least moderate evidence that bilingual children were less accurate at naming in 1 condition and at detecting mispronunciations in 3 of 6 contexts and were less accurate at judging semantic features of a referent when that referent was paired with orthographic information. Discussion Among children with typical development, there were few differences in novel word learning between monolingual and bilingual participants. When differences did occur, they suggested that bilinguals were more accepting of phonological variations of word productions than their monolingual peers.

Bilingual toddlers' comprehension of mixed sentences is asymmetrical across their two languages

In bilingual language environments, infants and toddlers listen to two separate languages during the same key years that monolingual children listen to just one and bilinguals rarely learn each of their two languages at the same rate. Learning to understand language requires them to cope with challenges not found in monolingual input, notably the use of two languages within the same utterance (e.g., Do you like the perro? or ¿Te gusta el doggy?). For bilinguals of all ages, switching between two languages can reduce the efficiency in real-time language processing. But language switching is a dynamic phenomenon in bilingual environments, presenting the young learner with many junctures where comprehension can be derailed or even supported. In this study, we tested 20 Spanish-English bilingual toddlers (18- to 30-months) who varied substantially in language dominance. Toddlers' eye movements were monitored as they looked at familiar objects and listened to single-language and mixed-language sentences in both of their languages. We found asymmetrical switch costs when toddlers were tested in their dominant versus non-dominant language, and critically, they benefited from hearing nouns produced in their dominant language, independent of switching. While bilingualism does present unique challenges, our results suggest a united picture of early monolingual and bilingual learning. Just like monolinguals, experience shapes bilingual toddlers' word knowledge, and with more robust representations, toddlers are better able to recognize words in diverse sentences.

Developmental change in tone perception in Mandarin monolingual, English monolingual, and Mandarin-English bilingual infants: Divergences between monolingual and bilingual learners

Most languages use lexical tone to discriminate the meanings of words. There has been recent interest in tracking the development of tone categories during infancy. These studies have focused largely on monolingual infants learning either a tone language or a non-tone language. It remains to be seen how bilingual infants learning one tone language (e.g., Mandarin) and one non-tone language (e.g., English) discriminate tones. Here, we examined infants' discrimination of two Mandarin tones pairs: one salient and one subtle. Discrimination was investigated in three groups: Mandarin-English bilinguals, English monolinguals, and Mandarin monolinguals at 6 months and 9 months of age in a cross-sectional design. Results demonstrated relatively strong Mandarin tone discrimination in Mandarin monolinguals, with salient tone discrimination at 6 months and both salient and subtle tone discrimination at 9 months. English monolinguals discriminated neither contrast at 6 months but discriminated the salient contrast at 9 months. Surprisingly, there was no evidence for tone discrimination in Mandarin-English bilingual infants. In a second experiment, 12- and 13-month-old Mandarin-English bilingual and English monolingual infants were tested to determine whether bilinguals would demonstrate tone sensitivity at a later age. Results revealed a lack of tone sensitivity at 12 or 13 months in bilingual infants, yet English monolingual infants were sensitive to both salient and subtle Mandarin tone contrasts at 12 or 13 months. Our findings provide evidence for age-related convergence in Mandarin tone discrimination in English and Mandarin monolingual infants and for a distinct pattern of tone discrimination in bilingual infants. Theoretical implications for phonetic category acquisition are discussed.

Monolingual and Bilingual Infants' Ability to Use Non-native Tone for Word Learning Deteriorates by the Second Year After Birth

Previous studies reported a non-native word learning advantage for bilingual infants at around 18 months. We investigated developmental changes in infant interpretation of sounds that aid in object mapping. Dutch monolingual and bilingual (exposed to Dutch and a second non-tone-language) infants' word learning ability was examined on two novel label-object pairings using syllables differing in Mandarin tones as labels (flat vs. falling). Infants aged 14-15 months, regardless of language backgrounds, were sensitive to violations in the label-objects pairings when lexical tones were switched compared to when they were the same as habituated. Conversely at 17-18 months, neither monolingual nor bilingual infants demonstrated learning. Linking with existing literature, infants' ability to associate non-native tones with meanings may be related to tonal acoustic properties and/or perceptual assimilation to native prosodic categories. These findings provide new insights into the relation between infant tone perception, learning, and interpretative narrowing from a developmental perspective.

How Native Prosody Affects Pitch Processing during Word Learning in Limburgian and Dutch Toddlers and Adults

In this study, Limburgian and Dutch 2.5- to 4-year-olds and adults took part in a word learning experiment. Following the procedure employed by Quam and Swingley (2010) and Singh et al. (2014), participants learned two novel word-object mappings. After training, word recognition was tested in correct pronunciation (CP) trials and mispronunciation (MP) trials featuring a pitch change. Since Limburgian is considered a restricted tone language, we expected that the pitch change would hinder word recognition in Limburgian, but not in non-tonal Dutch listeners. Contrary to our expectations, both Limburgian and Dutch children appeared to be sensitive to pitch changes in newly learned words, indicated by a significant decrease in target fixation in MP trials compared to CP trials. Limburgian and Dutch adults showed very strong naming effects in both trial types. The results are discussed against the background of the influence of the native prosodic system.

More Limitations to Monolingualism: Bilinguals Outperform Monolinguals in Implicit Word Learning

To succeed at cross-situational word learning, learners must infer word-object mappings by attending to the statistical co-occurrences of novel objects and labels across multiple encounters. While past studies have investigated this as a learning mechanism for infants and monolingual adults, bilinguals’ cross-situational word learning abilities have yet to be tested. Here, we compared monolinguals’ and bilinguals’ performance on a cross-situational word learning paradigm that featured phonologically distinct word pairs (e.g., BON-DEET) and phonologically similar word pairs that varied by a single consonant or vowel segment (e.g., BON-TON, DEET-DIT, respectively). Both groups learned the novel word-referent mappings, providing evidence that cross-situational word learning is a learning strategy also available to bilingual adults. Furthermore, bilinguals were overall more accurate than monolinguals. This supports that bilingualism fosters a wide range of cognitive advantages that may benefit implicit word learning. Additionally, response patterns to the different trial types revealed a relative difficulty for vowel minimal pairs than consonant minimal pairs, replicating the pattern found in monolinguals by Escudero et al. (2016) in a different English accent. Specifically, all participants failed to learn vowel contrasts differentiated by vowel height. We discuss evidence for this bilingual advantage as a language-specific or general advantage.

Limits on Monolingualism? A Comparison of Monolingual and Bilingual Infants' Abilities to Integrate Lexical Tone in Novel Word Learning

To construct their first lexicon, infants must determine the relationship between native phonological variation and the meanings of words. This process is arguably more complex for bilingual learners who are often confronted with phonological conflict: phonological variation that is lexically relevant in one language may be lexically irrelevant in the other. In a series of four experiments, the present study investigated English-Mandarin bilingual infants' abilities to negotiate phonological conflict introduced by learning both a tone and a non-tone language. In a novel word learning task, bilingual children were tested on their sensitivity to tone variation in English and Mandarin contexts. Their abilities to interpret tone variation in a language-dependent manner were compared to those of monolingual Mandarin learning infants. Results demonstrated that at 12-13 months, bilingual infants demonstrated the ability to bind tone to word meanings in Mandarin, but to disregard tone variation when learning new words in English. In contrast, monolingual learners of Mandarin did not show evidence of integrating tones into word meanings in Mandarin at the same age even though they were learning a tone language. However, a tone discrimination paradigm confirmed that monolingual Mandarin learning infants were able to tell these tones apart at 12-13 months under a different set of conditions. Later, at 17-18 months, monolingual Mandarin learners were able to bind tone variation to word meanings when learning new words. Our findings are discussed in terms of cognitive adaptations associated with bilingualism that may ease the negotiation of phonological conflict and facilitate precocious uptake of certain properties of each language.

Can bilingual children turn one language off? Evidence from perceptual switching

Bilinguals have the sole option of conversing in one language in spite of knowing two languages. The question of how bilinguals alternate between their two languages, activating and deactivating one language, is not well understood. In the current study, we investigated the development of this process by researching bilingual children's abilities to selectively integrate lexical tone based on its relevance in the language being used. In particular, the current study sought to determine the effects of global conversation-level cues versus local (within-word phonotactic) cues on children's tone integration in newly learned words. Words were taught to children via a conversational narrative, and word recognition was investigated using the intermodal preferential-looking paradigm. Children were tested on recognition of words with stimuli that were either matched or mismatched in tone in both English and Mandarin conversations. Results demonstrated that 3- to 4-year-olds did not adapt their interpretation of lexical tone changes to the language being spoken. In contrast, 4- to 5-year-olds were able to do so when supported by informative within-word cues. Results suggest that preschool children are capable of selectively activating a single language given word-internal cues to language.

Second label learning in bilingual and monolingual infants

Mutual exclusivity is the assumption that each object has only one category label. Prior research suggests that bilingual infants, unlike monolingual infants, fail to adhere to this assumption to guide word learning. Yet previous work has not addressed whether bilingual infants systematically interpret a novel word for a familiar object (i.e. an object with a known category label) as a second category label. We addressed this question by exploring bilingual and monolingual infants' use of mutual exclusivity in a task in which they heard a novel label for a familiar object with a salient color (e.g. an aqua-colored dog). They were subsequently tested with two trials that probed whether they interpreted the word as a second category label for the object (e.g. another word meaning dog) or as a label for one of the object's salient properties, namely its color (e.g. a word meaning aqua). Bilingual infants failed to adhere to mutual exclusivity and interpreted the novel word systematically as a second object category label for the familiar object. In contrast, consistent with their use of mutual exclusivity, monolingual infants rejected the novel word as a second category label, and instead showed some evidence of interpreting it as a property (color) term for the familiar object. The findings suggest that both bilingual and monolingual infants are systematic in their interpretation of a novel label for a familiar object, but that they show different interpretations of that label. We thus argue that theoretical accounts of early word learning must consider the crucial role of linguistic experience.

Bilingualism and increased attention to speech: Evidence from event-related potentials

A number of studies have shown that from an early age, bilinguals outperform their monolingual peers on executive control tasks. We previously found that bilingual children and adults also display greater attention to unexpected language switches within speech. Here, we investigated the effect of a bilingual upbringing on speech perception in one language. We recorded monolingual and bilingual toddlers' event-related potentials (ERPs) to spoken words preceded by pictures. Words matching the picture prime elicited an early frontal positivity in bilingual participants only, whereas later ERP amplitudes associated with semantic processing did not differ between groups. These results add to the growing body of evidence that bilingualism increases overall attention during speech perception whilst semantic integration is unaffected.

The Language and Literacy Development of Young Dual Language Learners: A Critical Review

The number of children living in the United States who are learning two languages is increasing greatly. However, relatively little research has been conducted on the language and literacy development of dual language learners (DLLs), particularly during the early childhood years. To summarize the extant literature and guide future research, a critical analysis of the literature was conducted. A search of major databases for studies on young typically developing DLLs between 2000-2011 yielded 182 peer-reviewed articles. Findings about DLL children's developmental trajectories in the various areas of language and literacy are presented. Much of these findings should be considered preliminary, because there were few areas where multiple studies were conducted. Conclusions were reached when sufficient evidence existed in a particular area. First, the research shows that DLLs have two separate language systems early in life. Second, differences in some areas of language development, such as vocabulary, appear to exist among DLLs depending on when they were first exposed to their second language. Third, DLLs' language and literacy development may differ from that of monolinguals, although DLLs appear to catch up over time. Fourth, little is known about factors that influence DLLs' development, although the amount of language exposure to and usage of DLLs' two languages appears to play key roles. Methodological issues are addressed, and directions for future research are discussed.

Phonetic processing when learning words

Infants have remarkable abilities to learn several languages. However, phonological acquisition in bilingual infants appears to vary depending on the phonetic similarities or differences of their two native languages. Many studies suggest that learning contrasts with different realizations in the two languages (e.g., the /p/, /t/, /k/ stops have similar VOT values in French, Spanish, Italian and European Portuguese, but can be confounded with the /b/, /d/, /g/ in German and English) poses a particular challenge. The current study explores how similarity or difference in the realization of phonetic contrasts affects word-learning outcomes. Bilingual infants aged 16 months were tested on their capacity to learn pairs of new words, differing by a phonological feature (voicing versus place) on their initial consonant. Two groups of infants were considered: bilinguals exposed to languages (French and either Spanish, Italian or European Portuguese) in which the contrasts tested are realized relatively similarly (“similar contrast” group) and bilinguals exposed to languages (French and either English or German) in which the contrasts are realized very differently (“different contrast” group). In the present word-learning situation, the “similar contrast” bilinguals successfully processed the relevant phonetic detail of the word forms, while the “different contrast” bilinguals failed. The present pattern reveals the impact on word learning of phonological differences between the two languages, which is consistent with studies reporting slight time course differences among bilinguals in phonological acquisition. In line with a larger literature on bilingual acquisition, these results provide further evidence that linguistic similarity or difference in the two languages influences the pattern of bilingual acquisition.

Bilingualism matters

The articles in this special issue provide a complex picture of acquisition in bilinguals in which the factors that contribute to patterns of performance in bilingual children’s two languages are myriad and diverse. The processes and contours of development in bilingual children are influenced, not only by the quantity, quality, and contexts of input, but by whether the child hears monolingual or bilingual speech, who is the source of that speech, the proportion of speakers of the heritage language in the community, the child’s birth order in the family, the family’s SES, the timing and the child’s stage of development, profile effects in performance, and characteristics of the languages being learned. One constant across the research is the finding that the majority language fairs well in development, while the minority language is threatened. The insights gained are relevant to future work on bilingual children, whether of a theoretical or applied focus.

You sound like Mommy

Previous research indicates that monolingual infants have difficulty learning minimal pairs (i.e., words differing by one phoneme) produced by a speaker uncharacteristic of their language environment and that bilinguals might share this difficulty. To clearly reveal infants’ underlying phonological representations, we minimized task demands by embedding target words in naming phrases, using a fully crossed, between-subjects experimental design. We tested 17-month-old French-English bilinguals’ ( N = 30) and English monolinguals’ ( N = 31) learning of a minimal pair (/k∊m/ – /g∊m/) produced by an adult bilingual or monolingual. Infants learned the minimal pair only when the speaker matched their language environment. This vulnerability to subtle changes in word pronunciation reveals that neither monolingual nor bilingual 17-month-olds possess fully generalizable phonological representations.

Perceptual narrowing in the context of increased variation: Insights from bilingual infants

Human infants become native-language listeners through a process of perceptual narrowing. Monolingual infants are initially sensitive to a wide range of language-relevant contrasts. However, as they mature and gain native-language experience, their sensitivity to nonnative contrasts declines. Here, we consider the case of infants growing up bilingual as a window into how increased variation affects early perceptual development. These infants encounter different meaningful contrasts in each of their languages, and must also attend to contrasts that occur between their languages. Bilingual infants share many classic developmental patterns with monolinguals. However, they also show unique developmental patterns in the perception of native distinctions such as U-shaped trajectories and dose-response relationships, and show some enhanced sensitivity to nonnative distinctions. Analogous developmental patterns can be observed in individuals exposed to two nonlinguistic systems in domains such as music and face perception. Some preliminary evidence suggests that bilingual individuals might retain more sensitivity to nonnative contrasts, reaching a less narrow end state than monolinguals. Nevertheless, bilingual infants do become perceptually specialized native listeners to both of their languages, despite increased variation and differing patterns of perceptual development in comparison to monolinguals.

One world, two languages: cross-language semantic priming in bilingual toddlers

The interconnectedness of bilingual memory remains a topic of great debate. Semantic priming provides a powerful methodological tool with which to investigate this issue in early bilingual toddlers. Semantic priming effects were investigated in 21 bilingual toddlers (2.5 years) within and across each of their languages. Results revealed the first evidence of cross-language and within-language semantic priming in bilingual toddlers. However, priming effects were only observed when the prime was presented in the dominant language and were comparable in magnitude within and across languages. Findings point to high interconnectivity across languages; however, there appear to be strong influences of language dominance on semantic facilitation. Findings serve to inform and refine developmental models of bilingual memory.

Lexical access and vocabulary development in very young bilinguals

This study compares lexical access and expressive and receptive vocabulary development in monolingual and bilingual toddlers. More specifically, the link between vocabulary size, production of translation equivalents, and lexical access in bilingual infants was examined as well as the relationship between the Communicative Development Inventories and the Computerized Comprehension Task. Twenty-five bilingual and 18 monolingual infants aged 24 months participated in this study. The results revealed significant differences between monolingual and bilinguals' expressive vocabulary size in L1 but similar total vocabularies. Performance on the Computerized Comprehension Task revealed no differences between the two groups on measures of both reaction time and accuracy, and a strong convergent validity of the Computerized Comprehension Task with the Communicative Development Inventories was observed for both groups. Bilinguals with a higher proportion of translation equivalents in their expressive vocabulary showed faster access to words in the Computerized Comprehension Task.

Bilingualism in the Early Years: What the Science Says

Many children in North America and around the world grow up exposed to two languages from an early age. Parents of bilingual infants and toddlers have important questions about the costs and benefits of early bilingualism, and how to best support language acquisition in their children. Here, we separate common myths from scientific findings to answer six of parents' most common questions about early bilingual development.

Language nonselective lexical access in bilingual toddlers

We examined how words from bilingual toddlers' second language (L2) primed recognition of related target words in their first language (L1). On critical trials, prime-target word pairs were either (a) phonologically related, with L2 primes overlapped phonologically with L1 target words [e.g., slide (L2 prime)-Kleid (L1 target, "dress")], or (b) phonologically related through translation, with L1 translations of L2 primes rhymed with the L1 target words [e.g., leg (L2 prime, L1 translation, "Bein")-Stein (L1 target, "stone"). Evidence of facilitated target recognition in the phonological priming condition suggests language nonselective access but not necessarily lexical access. However, a late interference effect on target recognition in the phonological priming through translation condition provides evidence for language nonselective lexical access: The L2 prime (leg) could influence L1 target recognition (Stein) in this condition only if both the L2 prime (leg) and its L1 translation ("Bein") were concurrently activated. In addition, age- and gender-matched monolingual toddler controls showed no difference between conditions, providing further evidence that the results with bilingual toddlers were driven by cross-language activation. The current study, therefore, presents the first-ever evidence of cross-talk between the two languages of bilinguals even as they begin to acquire fluency in their second language.

Perceptual foundations of bilingual acquisition in infancy

Infants are prepared by biology to acquire language, but it is the native language(s) they must learn. Over the first weeks and months of life, infants learn about the sounds and sights of their native language, and use that perceptual knowledge to pull out words and bootstrap grammar. In this paper, I review research showing that infants growing up bilingual learn the properties of each of the their two languages simultaneously, while nonetheless keeping them apart. Thus, they use perceptual learning to break into the properties of each of the two native languages. While the fundamental process of language acquisition is the same whether one or two languages are being acquired, cognitive advantages accrue from the task of language separation, and processing costs accrue from the more minimal input received in each of the two languages. I conclude by suggesting that when there are sufficient cues to which language is being used, the cognitive advantages that accrue from language separation enable the bilingual infant to move forward in language acquisition even in the face of processing costs.

Influences of lexical tone and pitch on word recognition in bilingual infants

Infants' abilities to discriminate native and non-native phonemes have been extensively investigated in monolingual learners, demonstrating a transition from language-general to language-specific sensitivities over the first year after birth. However, these studies have mostly been limited to the study of vowels and consonants in monolingual learners. There is relatively little research on other types of phonetic segments, such as lexical tone, even though tone languages are very well represented across languages of the world. The goal of the present study is to investigate how Mandarin Chinese-English bilingual learners contend with non-phonemic pitch variation in English spoken word recognition. This is contrasted with their treatment of phonemic changes in lexical tone in Mandarin spoken word recognition. The experimental design was cross-sectional and three age-groups were sampled (7.5months, 9months and 11months). Results demonstrated limited generalization abilities at 7.5months, where infants only recognized words in English when matched in pitch and words in Mandarin that were matched in tone. At 9months, infants recognized words in Mandarin Chinese that matched in tone, but also falsely recognized words that contrasted in tone. At this age, infants also recognized English words whether they were matched or mismatched in pitch. By 11months, infants correctly recognized pitch-matched and - mismatched words in English but only recognized tonal matches in Mandarin Chinese.

Cognitive and linguistic correlates of early exposure to more than one language

This chapter reviews recent studies of cognitive and linguistic correlates of exposure to two languages in infancy and early childhood. Most of the studies reviewed directly compare monolingual children to those who are exposed to two languages. The cognitive correlates include enhanced executive functioning (especially inhibitory control), and Theory of Mind. The linguistic correlates include smaller vocabularies in each language, different word-learning strategies, slower lexical access, and enhanced pragmatic and metalinguistic skills. Issues in interpreting group differences, in particular, whether such differences should be interpreted as deficits, are discussed.

The acquisition of phonetic categories in bilingual infants: new data from an anticipatory eye movement paradigm

Contrasting results have been reported regarding the phonetic acquisition of bilinguals. A lack of discrimination has been observed for certain native contrasts in 8-month-old Catalan-Spanish bilingual infants (Bosch & Sebastián-Gallés, 2003a), though not in French-English bilingual infants (Burns, Yoshida, Hill & Werker, 2007; Sundara, Polka & Molnar, 2008). At present, the data for Catalan-Spanish bilinguals constitute an exception in the early language acquisition literature. This study contributes new findings that show that Catalan-Spanish bilingual infants do not lose the capacity to discriminate native contrasts. We used an adaptation of the anticipatory eye movement paradigm (AEM; McMurray & Aslin, 2004) to explore this question. In two experiments we tested the ability of infants from Catalan and Spanish monolingual families and from Catalan-Spanish bilingual families to discriminate a Spanish-Catalan common and a Catalan-specific vowel contrast. Results from both experiments revealed that Catalan-Spanish bilingual infants showed the same discrimination abilities as those shown by their monolingual peers, even in a phonetic contrast that had not been discriminated in previous studies. Our results demonstrate that discrimination can be observed in 8-month-old bilingual infants when tested with a measure not based on recovery of attention. The high ratio of cognates in Spanish and Catalan may underlie the reason why bilinguals failed to discriminate the native vowels when tested with the familiarization-preference procedure but succeeded with the AEM paradigm.

Event-related potential correlates of language change detection in bilingual toddlers

Children raised in a bilingual environment are faced with the daunting task of learning to extract meaning from language input that can differ between caregivers but, depending on the social context, also within caregivers. Here, we investigated monolingual and bilingual toddlers' brain responses to an unexpected language change. We presented 2-3 year old children with picture-word pairs and occasionally changed the language of the spoken word while recording event-related potentials (ERPs). In line with previous results obtained in adults, bilingual children differentiated between the languages of input faster than their monolingual peers, i.e., within 200 ms of spoken word onset, a time range previously associated with lexical access. However, while adult bilinguals displayed a late stimulus re-evaluation ERP response to a language change, no such modulation was found in bilingual toddlers. These results suggest that although bilingual individuals are sensitive to phonemic language cues already from an early age, language awareness and language monitoring mechanisms probably develop later in life.

The effects of bilingualism on toddlers' executive functioning

Bilingual children have been shown to outperform monolingual children on tasks measuring executive functioning skills. This advantage is usually attributed to bilinguals' extensive practice in exercising selective attention and cognitive flexibility during language use because both languages are active when one of them is being used. We examined whether this advantage is observed in 24-month-olds who have had much less experience in language production. A battery of executive functioning tasks and the cognitive scale of the Bayley test were administered to 63 monolingual and bilingual children. Native bilingual children performed significantly better than monolingual children on the Stroop task, with no difference between groups on the other tasks, confirming the specificity of bilingual effects to conflict tasks reported in older children. These results demonstrate that bilingual advantages in executive control emerge at an age not previously shown.

Word learning and lexical development across the lifespan

Word learning is one of the core components of language acquisition. In this article, we provide an overview of the theme issue on word learning, describing some of the ways in which research in the area has progressed and diverged. In recent years, word learning has become central in a wider range of research areas, and is important to research on adult, as well as child and infant language. We introduce 10 papers that cover the recent developments from a wide range of perspectives, focusing on developmental research, the influence of reading skills, neuroimaging and the relationship between word learning and general models of memory.

Bilingual beginnings to learning words

At the macrostructure level of language milestones, language acquisition follows a nearly identical course whether children grow up with one or with two languages. However, at the microstructure level, experimental research is revealing that the same proclivities and learning mechanisms that support language acquisition unfold somewhat differently in bilingual versus monolingual environments. This paper synthesizes recent findings in the area of early bilingualism by focusing on the question of how bilingual infants come to apply their phonetic sensitivities to word learning, as they must to learn minimal pair words (e.g. 'cat' and 'mat'). To this end, the paper reviews antecedent achievements by bilinguals throughout infancy and early childhood in the following areas: language discrimination and separation, speech perception, phonetic and phonotactic development, word recognition, word learning and aspects of conceptual development that underlie word learning. Special consideration is given to the role of language dominance, and to the unique challenges to language acquisition posed by a bilingual environment.