Dual language input and the impact of language separation on early lexical development

The contribution of the amount of linguistic exposure to bilingual language development: Longitudinal evidence from preschool years

This study examined the influence of linguistic input on the development of productive and receptive skills across three fundamental language domains: lexico-semantics, syntax, and phonology. Seventy-one (35 female) Basque-Spanish bilingual children were assessed at three time points (Fall 2018, Summer 2019, Winter 2021), between 4 and 6 years of age, by specifically examining language knowledge and spontaneous language use in each language. A direct impact of the amount of linguistic exposure on the longitudinal growth of lexico-semantic and syntactic abilities was observed in both languages. While phonological skills were not directly influenced by exposure, they were more proficient in the more exposed language. The use of lexically diverse and syntactically rich utterances developed relatively later than language knowledge, both supported by the amount of linguistic exposure.

Early language experience modulates the tradeoff between acoustic-temporal and lexico-semantic cortical tracking of speech

Cortical tracking of speech is relevant for the development of speech perception skills. However, no study to date has explored whether and how cortical tracking of speech is shaped by accumulated language experience, the central question of this study. In 35 bilingual children (6-year-old) with considerably bigger experience in one language, we collected electroencephalography data while they listened to continuous speech in their two languages. Cortical tracking of speech was assessed at acoustic-temporal and lexico-semantic levels. Children showed more robust acoustic-temporal tracking in the least experienced language, and more sensitive cortical tracking of semantic information in the most experienced language. Additionally, and only for the most experienced language, acoustic-temporal tracking was specifically linked to phonological abilities, and lexico-semantic tracking to vocabulary knowledge. Our results indicate that accumulated linguistic experience is a relevant maturational factor for the cortical tracking of speech at different levels during early language acquisition.

Revisiting perceptual sensitivity to non-native speech in a diverse sample of bilinguals

Werker and Tees (1984) prompted decades of research attempting to detail the paths infants take towards specialisation for the sounds of their native language(s). Most of this research has examined the trajectories of monolingual children. However, it has also been proposed that bilinguals, who are exposed to greater phonetic variability than monolinguals and must learn the rules of two languages, may remain perceptually open to non-native language sounds later into life than monolinguals. Using a visual habituation paradigm, the current study tests this question by comparing 15- to 18-month-old monolingual and bilingual children's developmental trajectories for non-native phonetic consonant contrast discrimination. A novel approach to the integration of stimulus presentation software with eye-tracking software was validated for objective measurement of infant looking time. The results did not support the hypothesis of a protracted period of sensitivity to non-native phonetic contrasts in bilingual compared to monolingual infants. Implications for diversification of perceptual narrowing research and implementation of increasingly sensitive measures are discussed.

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.

Bilingual toddlers show increased attention capture by static faces compared to monolinguals

Bilingual infants rely differently than monolinguals on facial information, such as lip patterns, to differentiate their native languages. This may explain, at least in part, why young monolinguals and bilinguals show differences in social attention. For example, in the first year, bilinguals attend faster and more often to static faces over non-faces than do monolinguals (Mercure et al., 2018). However, the developmental trajectories of these differences are unknown. In this pre-registered study, data were collected from 15- to 18-month-old monolinguals (English) and bilinguals (English and another language) to test whether group differences in face-looking behaviour persist into the second year. We predicted that bilinguals would orient more rapidly and more often to static faces than monolinguals. Results supported the first but not the second hypothesis. This suggests that, even into the second year of life, toddlers' rapid visual orientation to static social stimuli is sensitive to early language experience.

Comparing Different Measures of Bilingual Input Derived From Naturalistic Daylong Recordings

PURPOSE

Measuring language input, especially for infants growing up in bilingual environments, is challenging. Although the ways to measure input have expanded rapidly in recent years, there are many unresolved issues. In this study, we compared different measurement units and sampling methods used to estimate bilingual input in naturalistic daylong recordings.

METHOD

We used the Language Environment Analysis system to obtain and process naturalistic daylong recordings from 21 French-English bilingual families with an infant at 10 and 18 months of age. We examined global and context-specific input estimates and their relation with infant vocal activeness (i.e., volubility) when input was indexed by different units (adult word counts, speech duration, 30-s segment counts) and using different sampling methods (every-other-segment, top-segment).

RESULTS

Input measures indexed by different units were strongly and positively correlated with each other and yielded similar results regarding their relation with infant volubility. As for sampling methods, sampling every other 30-s segment was representative of the entire corpus. However, sampling the top segments with the densest input was less representative and yielded different results regarding their relation with infant volubility.

CONCLUSIONS

How well the input that a child receives throughout a day is portrayed by a selected sample and correlates with the child's vocal activeness depends on the choice of input units and sampling methods. Different input units appear to generate consistent results, while caution should be taken when choosing sampling methods.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.22335688.

LANGUAGE EXPOSURE PREDICTS CHILDREN'S PHONETIC PATTERNING: EVIDENCE FROM LANGUAGE SHIFT

Although understanding the role of the environment is central to language acquisition theory, rarely has this been studied for children's phonetic development, and receptive and expressive language experiences in the environment are not distinguished. This last distinction may be crucial for child speech production in particular, because production requires coordination of low-level speech-motor planning with high-level linguistic knowledge. In this study, the role of the environment is evaluated in a novel way-by studying phonetic development in a bilingual community undergoing rapid language shift. This sociolinguistic context provides a naturalistic gradient of the amount of children's exposure to two languages and the ratio of expressive to receptive experiences. A large-scale child language corpus encompassing over 500 hours of naturalistic South Bolivian Quechua and Spanish speech was efficiently annotated for children's and their caregivers' bilingual language use. These estimates were correlated with children's patterns in a series of speech production tasks. The role of the environment varied by outcome: children's expressive language experience best predicted their performance on a coarticulation-morphology measure, while their receptive experience predicted performance on a lower-level measure of vowel variability. Overall these bilingual exposure effects suggest a pathway for children's role in language change whereby language shift can result in different learning outcomes within a single speech community. Appropriate ways to model language exposure in development are discussed.

Code-switching in parents' everyday speech to bilingual infants

Code-switching is a common phenomenon in bilingual communities, but little is known about bilingual parents' code-switching when speaking to their infants. In a pre-registered study, we identified instances of code-switching in day-long at-home audio recordings of 21 French-English bilingual families in Montreal, Canada, who provided recordings when their infant was 10 and 18 months old. Overall, rates of infant-directed code-switching were low, averaging 7 times per hour (6 times per 1,000 words) at 10 months and increasing to 28 times per hour (18 times per 1,000 words) at 18 months. Parents code-switched more between sentences than within a sentence; this pattern was even more pronounced when infants were 18 months than when they were 10 months. The most common apparent reasons for code-switching were to bolster their infant's understanding and to teach vocabulary words. Combined, these results suggest that bilingual parents code-switch in ways that support successful bilingual language acquisition.

Shared Multimodal Input Through Social Coordination: Infants With Monolingual and Bilingual Learning Experiences

A growing number of children in the United States are exposed to multiple languages at home from birth. However, relatively little is known about the early process of word learning—how words are mapped to the referent in their child-centered learning experiences. The present study defined parental input operationally as the integrated and multimodal learning experiences as an infant engages with his/her parent in an interactive play session with objects. By using a head-mounted eye tracking device, we recorded visual scenes from the infant’s point of view, along with the parent’s social input with respect to gaze, labeling, and actions of object handling. Fifty-one infants and toddlers (aged 6–18 months) from an English monolingual or a diverse bilingual household were recruited to observe the early multimodal learning experiences in an object play session. Despite that monolingual parents spoke more and labeled more frequently relative to bilingual parents, infants from both language groups benefit from a comparable amount of socially coordinated experiences where parents name the object while the object is looked at by the infant. Also, a sequential path analysis reveals multiple social coordinated pathways that facilitate infant object looking. Specifically, young children’s attention to the referent objects is directly influenced by parent’s object handling. These findings point to the new approach to early language input and how multimodal learning experiences are coordinated socially for young children growing up with monolingual and bilingual learning contexts.

Effects of language mixing on bilingual children's word learning

Language mixing is common in bilingual children's learning environments. Here, we investigated effects of language mixing on children's learning of new words. We tested two groups of 3-year-old bilinguals: French-English (Experiment 1) and Spanish-English (Experiment 2). Children were taught two novel words, one in single-language sentences ("Look! Do you see the dog on the teelo?") and one in mixed-language sentences with a mid-sentence language switch ("Look! Do you see the chien/perro on the walem?"). During the learning phase, children correctly identified novel targets when hearing both single-language and mixed-language sentences. However, at test, French-English bilinguals did not successfully recognize the word encountered in mixed-language sentences. Spanish-English bilinguals failed to recognize either word, which underscores the importance of examining multiple bilingual populations. This research suggests that language mixing may sometimes hinder children's encoding of novel words that occur downstream, but leaves open several possible underlying mechanisms.

Efficient Estimation of Children's Language Exposure in Two Bilingual Communities

Purpose The language that children hear early in life is associated with their speech-language outcomes. This line of research relies on naturalistic observations of children's language input, often captured with daylong audio recordings. However, the large quantity of data that daylong recordings generate requires novel analytical tools to feasibly parse thousands of hours of naturalistic speech. This study outlines a new approach to efficiently process and sample from daylong audio recordings made in two bilingual communities, Spanish-English in the United States and Quechua-Spanish in Bolivia, to derive estimates of children's language exposure. Method We employed a general sampling with replacement technique to efficiently estimate two key elements of children's early language environments: (a) proportion of child-directed speech (CDS) and (b) dual language exposure. Proportions estimated from random sampling of 30-s segments were compared to those from annotations over the entire daylong recording (every other segment), as well as parental report of dual language exposure. Results Results showed that approximately 49 min from each recording or just 7% of the overall recording was required to reach a stable proportion of CDS and bilingual exposure. In both speech communities, strong correlations were found between bilingual language estimates made using random sampling and all-day annotation techniques. A strong association was additionally found for CDS estimates in the United States, but this was weaker at the Bolivian site, where CDS was less frequent. Dual language estimates from the audio recordings did not correspond well to estimates derived from parental report collected months apart. Conclusions Daylong recordings offer tremendous insight into children's daily language experiences, but they will not become widely used in developmental research until data processing and annotation time substantially decrease. We show that annotation based on random sampling is a promising approach to efficiently estimate ambient characteristics from daylong recordings that cannot currently be estimated via automated methods.