A multilab 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) compared with adult-directed speech (ADS). Yet IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multisite 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 multilab ManyBabies 1 project, we compared preference for North American English (NAE) IDS in lab-matched samples of 333 bilingual and 384 monolingual infants tested in 17 labs in seven countries. The tested infants were in two age groups: 6 to 9 months and 12 to 15 months. We found that bilingual and monolingual infants both preferred IDS to ADS, and the two groups did not differ in terms of the overall magnitude of this preference. However, among bilingual infants who were acquiring NAE as a native language, greater exposure to NAE was associated with a stronger IDS preference. These findings extend the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger IDS preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes similar contributions 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

Growing up bilingual: examining the language input and word segmentation abilities of bilingual infants

Infants’ early language experiences play a critical role on their language development. In this dissertation, I explored the nature of this relationship in a bilingual context. Specifically, I investigated how bilingual caregivers are providing language input to their infants, and how global measures of this bilingual experience affect early word segmentation (i.e., the ability to recognize words in a sentential context). This work is important for understanding the factors that contribute to the developmental trajectory and processing capacities of bilingual infants. In the first part of this dissertation, I assessed research methods for examining the language input to bilingual infants. To do so, I recruited twenty-one French-English bilingual families with a 10-month-old infant from Montréal, Canada. These families completed language interviews and contributed three full-day recordings at home using the LENA (Language Environment Analysis) recording system. Chapter 2 provides support for using the LENA recording system for investigating the language input in bilingual infants, and Chapter 3 shows that caregivers are reliable at describing their infants’ language experience at home. Next, I described the variability in language experiences within bilingual infants, and how these language experiences might affect word segmentation. In Chapter 4, I recruited 8- and 10-month-old infants from monolingual and bilingual homes. Our findings confirm that monolingual infants can segment bisyllabic words in their native language, but not a non-native language. Critically, our findings reveal that some bilingual infants are able to segment bisyllabic words in both of their native languages by 8-months of age. Interestingly, exploratory analyses suggest that infants’ word segmentation skills in our dual-language task are bolstered if they hear more language mixing from their caregivers. In sum, this dissertation contributes to the growing literature that highlights the wide variability in bilingual language experiences, and their effects on early speech processing skills. Indeed, examining the language experiences and skills of bilingual-learning infants provides us with a unique lens for investigating language acquisition and development

Growing up bilingual:examining the language input and word segmentation abilities of bilingual infants

Infants' early language experiences play a critical role on their language development. In this dissertation, I explored the nature of this relationship in a bilingual context. Specifically, I investigated how bilingual caregivers are providing language input to their infants, and how global measures of this bilingual experience affect early word segmentation (i.e., the ability to recognize words in a sentential context). This work is important for understanding the factors that contribute to the developmental trajectory and processing capacities of bilingual infants. In the first part of this dissertation, I assessed research methods for examining the language input to bilingual infants. To do so, I recruited twenty-one French-English bilingual families with a 10-month-old infant from Montréal, Canada. These families completed language interviews and contributed three full-day recordings at home using the LENA (Language Environment Analysis) recording system. Chapter 2 provides support for using the LENA recording system for investigating the language input in bilingual infants, and Chapter 3 shows that caregivers are reliable at describing their infants' language experience at home. Next, I described the variability in language experiences within bilingual infants, and how these language experiences might affect word segmentation. In Chapter 4, I recruited 8- and 10-month-old infants from monolingual and bilingual homes. Our findings confirm that monolingual infants can segment bisyllabic words in their native language, but not a non-native language. Critically, our findings reveal that some bilingual infants are able to segment bisyllabic words in both of their native languages by 8-months of age. Interestingly, exploratory analyses suggest that infants' word segmentation skills in our dual-language task are bolstered if they hear more language mixing from their caregivers. In sum, this dissertation contributes to the growing literature that highlights the wide variability in bilingual language experiences, and their effects on early speech processing skills. Indeed, examining the language experiences and skills of bilingual-learning infants provides us with a unique lens for investigating language acquisition and development.Les expériences linguistiques précoces des bébés jouent un rôle important dans leur développement langagier. Dans cette dissertation, j'ai exploré la nature de cette relation dans un contexte bilingue. Plus précisément, j'ai étudié comment les parents bilingues fournissent l'apport langagier à leurs bébés, et comment des mesures globales de cette exposition bilingue influencent la segmentation précoce des mots (c.-à-d. la capacité de reconnaitre des formes de mots dans le contexte de phrases). Les présents travaux sont importants afin de mieux comprendre les facteurs qui contribuent à la trajectoire développementale et aux capacités de traitement des bébés bilingues. Dans la première partie de cette dissertation, j'ai comparé des méthodes de recherche servant à l'observation de l'apport langagier chez les bébés bilingues. Pour ce faire, j'ai recruté vingt-et-une familles bilingues en français et en anglais de Montréal, Canada, ayant un bébé de 10 mois. Ces familles ont pris part à des entrevues sur le langage et ont contribué trois journées entières d'enregistrements à la maison en utilisant le système d'enregistrement LENA ("Language Environment Analysis", ou analyse de l'environnement langagier). Le Chapitre 2 soutient l'utilisation du système d'enregistrement LENA pour l'étude de l'apport langagier chez les bébés bilingues, et le Chapitre 3 démontre que les parents décrivent l'exposition langagière de leurs enfants à la maison de façon juste.Ensuite, j'ai décrit la variabilité observée dans les expériences langagières parmi les bébés bilingues et j'ai discuté la façon dont ces expériences langagières peuvent possiblement influencer la segmentation des mots. Dans le Chapitre 4, j'ai recruté des bébés de 8 et 10 mois de familles unilingues et bilingues. Nos résultats confirment que les bébés unilingues peuvent segmenter des mots à deux syllabes dans leur langue maternelle, mais pas dans une langue n'étant pas leur langue maternelle. Crucialement, nos résultats révèlent que les bébés bilingues peuvent, dès l'âge de 8 mois, segmenter des mots à deux syllabes dans chacune de leurs langues maternelles. Il est intéressant de noter que des analyses exploratoires suggèrent que dans notre tâche langagière bilingue, la capacité de segmentation de mots des bébés est renforcée si ceux-ci entendent plus de mélanges de langues par leurs parents.Pour conclure, cette dissertation contribue à la littérature de plus en plus abondante mettant l'accent sur la grande variabilité en ce qui a trait aux expériences langagières bilingues et leurs effets sur les capacités de traitement précoce du langage. En effet, l'exploration des expériences langagières et habiletés des bébés bilingues nous offre une occasion unique d'étudier l'acquisition et le développement du langage

Recognizing voices through a cochlear implant: A systematic review

Objective: Some cochlear implant (CI) users report having difficulty accessing indexical information in the speech signal, presumably due to the transformation from acoustic to electric signal in CI devices. The purpose of this paper was to systematically review and evaluate the existing research on talker perception in CI users. Specifically, we reviewed the performance of CI users in talker discrimination, gender identification, and talker recognition tasks in relation to performance by normal-hearing (NH) listeners. We also examined the different factors (such as participant, hearing and device characteristics) that might influence talker perception. Design: We completed a systematic search of the literature with select keywords using citation aggregation software to search Google Scholar. We included primary reports that had at least one group of participants with cochlear implants, and had an experimental task that measured talker or voice perception. Each included study was also evaluated for quality of evidence. Results: The initial search resulted in 1239 references, which were first screened for inclusion and then evaluated in full. Thirty-nine studies examining talker identification, talker discrimimnation, and gender discrimination were included in the final review. The majority of studies were focused on adult postlingual cochlear implant users, with a few studies focused on prelingual implant users. As a group, CI users generally performed above chance in talker perception tasks, but performed worse than NH controls. Nonetheless, a subset of CI users reached the same level of performance as NH participants. CI users relied more heavily on fundamental frequency over vocal tract length cues to distinguish talkers compared to NH listeners. Within groups of CI users, there is moderate evidence for a bimodal benefit for talker perception, and there are mixed findings about the effects of hearing experience. Performance in talker discrimination tasks was related to other linguistic tasks, including word recognition. Conclusion: The current review highlights the challenges faced by CI users in tracking and recognizing voices and how they adapt to it. There is clear evidence that CI users can process indexical information, albeit differently and more effortfully than NH listeners. Recent work has begun to describe some of the factors that might ease the challenges of talker perception in CI users, but further high-quality research is needed to disentangle some of the mixed findings. We conclude by suggesting some future avenues of research to optimize real-world speech outcomes

Infants use disambiguation to learn new voices

The ability to identify individuals by voice is a fundamental communicative ability. However, little is known about the expectations that infants hold when learning the voices of unfamiliar people. Here, the voice-learning skills of 4- and 8-month-old infants (N=53) were tested using a preferential looking task that involved audio-visual stimuli of their mothers and other unfamiliar women. Findings reveal that the expectation that novel voices map on to novel faces emerges as early as 4 months of age, and that infants can retain learning of face-voice pairings via disambiguation by 8 months of age. This study provides new insights about voice learning in infancy, and the mechanisms by which infants integrate the visual and auditory features of individuals around them

Comparing different measures of bilingual input derived from naturalistic day-long 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 the current study, we compared different measurement units and sampling methods used to estimate bilingual input in naturalistic daylong recordings. Method: We used Language Environment Analysis (LENA) systems 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-second 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-second 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. How to cite this article: Ruan, Y., Orena, A. J., & Polka, L. (2023). Comparing Different Measures of Bilingual Input Derived From Naturalistic Daylong Recordings. Journal of Speech, Language, and Hearing Research, 66(5), 1618-1630. https://doi.org/10.1044/2023_JSLHR-22-0018

Identifying bilingual talkers after a language switch: Language experience matters

The current study investigates the role of language experience in generalizing indexical information across languages within bilingual speech. Participants (n = 48) learned to identify bilingual talkers speaking in one of their languages and were then tested on their ability to identify the same talker when speaking the same language and when speaking their other language. Both monolingual and bilingual participants showed above chance performance in identifying the talkers in both language contexts. However, bilingual participants outperformed monolinguals in generalizing knowledge about the speaker’s voice across their two familiar languages, which may be driven by their experience with language mixing

Reliability of the Language Environment Analysis (LENA) in French-English Bilingual Speech

Purpose: This study examined the utility of the Language ENvironment Analysis (LENA) recording system for investigating the language input to bilingual infants. Method: Twenty-one French-English bilingual families with a 10-month-old infant participated in this study. Using the LENA recording system, each family contributed three full days of recordings within a one-month period. A portion of these recordings (945 minutes) were manually transcribed, and the word counts from these transcriptions were compared against the LENA-generated adult word counts. Results: Data analyses reveal that the LENA algorithms were reliable in counting words in both Canadian English and Canadian French, even when both languages are present in the same recording. While the LENA system tended to underestimate the amount of speech in the recordings, there was a strong correlation between the LENA-generated and human transcribed adult word counts for each language. Importantly, this relationship holds when accounting for different-gendered and different-accented speech. Conclusions: The LENA recording system is a reliable tool for estimating word counts, even for bilingual input. Special considerations and limitations for using the LENA recording system in a bilingual population are discussed. These results open up possibilities for investigating caregiver talk to bilingual infants in more detail

What do bilingual infants actually hear? Evaluating measures of language input to bilingual-learning 10-month-olds

Examining how bilingual infants experience their dual language input is important for understanding bilingual language acquisition. To assess these language experiences, researchers typically conduct language interviews with caregivers. However, little is known about the reliability of these parent reports in describing how bilingual children actually experience dual language input. Here, we explored the quantitative nature of dual language input to bilingual infants. Further, we described some of the heterogeneity of bilingual exposure in a sample of French-English bilingual families. Participants were twenty-one families with a 10-month-old infant residing in Montréal, Canada. First, we conducted language interviews with the caregivers. Then, each family completed three full-day recordings at home using the LENA (Language Environment Analysis) recording system. Results showed that children’s proportion exposure to each language was consistent across the two measurement approaches, indicating that parent reports are reliable for assessing a bilingual child’s language experiences. Further exploratory analyses revealed three unique findings: (1) there can be considerable variability in the absolute amount of input among infants hearing the same proportion of input, (2) infants can hear different proportions of language input when considering infant-directed versus overheard speech, (3) proportion of language input can vary by day, depending on who is caring for the infant. We conclude that collecting naturalistic recordings is complementary to parent-report measures for assessing infant’s language experiences and for establishing bilingual profiles

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