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.

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.

Recognizing Voices Through a Cochlear Implant: A Systematic Review of Voice Perception, Talker Discrimination, and Talker Identification.

OBJECTIVE: Some cochlear implant (CI) users report having difficulty accessing indexical information in the speech signal, presumably due to limitations in the transmission of fine spectrotemporal cues. The purpose of this review article was to systematically review and evaluate the existing research on talker processing in CI users. Specifically, we reviewed the performance of CI users in three types of talker- and voice-related tasks. We also examined the different factors (such as participant, hearing, and device characteristics) that might influence performance in these specific tasks. DESIGN: We completed a systematic search of the literature with select key words using citation aggregation software to search Google Scholar. We included primary reports that tested (a) talker discrimination, (b) voice perception, and (c) talker identification. Each report must have had at least one group of participants with CIs. Each included study was also evaluated for quality of evidence. RESULTS: The searches resulted in 1,561 references, which were first screened for inclusion and then evaluated in full. Forty-three studies examining talker discrimination, voice perception, and talker identification were included in the final review. Most studies were focused on postlingually deafened and implanted adult CI users, with fewer studies focused on prelingual implant users. In general, CI users performed above chance in these tasks. When there was a difference between groups, CI users performed less accurately than their normal-hearing (NH) peers. A subset of CI users reached the same level of performance as NH participants exposed to noise-vocoded stimuli. Some studies found that CI users and NH participants relied on different cues for talker perception. Within groups of CI users, there is moderate evidence for a bimodal benefit for talker processing, and there are mixed findings about the effects of hearing experience. CONCLUSIONS: The current review highlights the challenges faced by CI users in tracking and recognizing voices and how they adapt to it. Although large variability exists, there is evidence that CI users can process indexical information from speech, though with less accuracy than their NH peers. Recent work has described some of the factors that might ease the challenges of talker processing in CI users. We conclude by suggesting some future avenues of research to optimize real-world speech outcomes.

Learning to Recognize Unfamiliar Voices: An Online Study With 12- and 24-Month-Olds.

Young infants are attuned to the indexical properties of speech: they can recognize highly familiar voices and distinguish them from unfamiliar voices. Less is known about how and when infants start to recognize unfamiliar voices, and to map them to faces. This skill is particularly challenging when portions of the speaker's face are occluded, as is the case with masking. Here, we examined voice-face recognition abilities in infants 12 and 24 months of age. Using the online Lookit platform, children saw and heard four different speakers produce words with sonorous phonemes (high talker information), and words with phonemes that are less sonorous (low talker information). Infants aged 24 months, but not 12 months, were able to learn to link the voices to partially occluded faces of unfamiliar speakers, and only when the words were produced with high talker information. These results reveal that 24-month-old infants can encode and retrieve indexical properties of an unfamiliar speaker's voice, and they can access this information even when visual access to the speaker's mouth is blocked.

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.

Infants' Mapping of New Faces to New Voices.

The ability to identify individuals by voice is fundamental for communication. However, little is known about the expectations that infants hold when learning unfamiliar voices. Here, the voice-learning skills of 4- and 8-month-olds (N = 53; 29 girls, 14 boys of various ethnicities) were tested using a preferential-looking task that involved audiovisual stimuli of their mothers and other unfamiliar women. Findings reveal that the expectation that novel voices map on to novel faces emerges between 4 and 8 months of age, and that infants can retain learning of face-voice pairings via nonostensive cues by 8 months of age. This study provides new insights about infants' use of disambiguation and fast mapping in early voice learning.

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.

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. Furthermore, we described some of the heterogeneity of bilingual exposure in a sample of French-English bilingual families. Participants were 21 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 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: (a) there can be considerable variability in the absolute amount of input among infants hearing the same proportion of input, (b) infants can hear different proportions of language input when considering infant-directed versus overheard speech, (c) 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.

Reliability of the Language Environment Analysis Recording System in Analyzing 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 3 full days of recordings within a 1-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.

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.

Monolingual and bilingual infants' word segmentation abilities in an inter-mixed dual-language task.

Previous studies show that young monolingual infants use language-specific cues to segment words in their native language. Here, we asked whether 8 and 10-month-old infants (N = 84) have the capacity to segment words in an inter-mixed bilingual context. Infants heard an English-French mixed passage that contained one target word in each language, and were then tested on their recognition of the two target words. The English-monolingual and French-monolingual infants showed evidence of segmentation in their native language, but not in the other unfamiliar language. As a group, the English-French bilingual infants segmented in both of their native languages. However, exploratory analyses suggest that exposure to language mixing may play a role in bilingual infants' segmentation skills. Taken together, these results indicate a close relation between language experience and word segmentation skills.

Segmenting words from fluent speech during infancy - challenges and opportunities in a bilingual context.

Previous research shows that word segmentation is a language-specific skill. Here, we tested segmentation of bi-syllabic words in two languages (French; English) within the same infants in a single test session. In Experiment 1, monolingual 8-month-olds (French; English) segmented bi-syllabic words in their native language, but not in an unfamiliar and rhythmically different language. In Experiment 2, bilingual infants acquiring French and English demonstrated successful segmentation for French when it was tested first, but not for English and not for either language when tested second. There were no effects of language exposure on this pattern of findings. In Experiment 3, bilingual infants segmented the same English materials used in Experiment 2 when they were tested using the standard segmentation procedure, which provided more exposure to the test stimuli. These findings show that segmenting words in both their native languages in the dual-language task poses a distinct challenge for bilingual 8-month-olds acquiring French and English. Further research exploring early word segmentation will advance our understanding of bilingual acquisition and expand our fundamental knowledge of language and cognitive development.

Reading ability influences native and non-native voice recognition, even for unimpaired readers.

Research suggests that phonological ability exerts a gradient influence on talker identification, including evidence that adults and children with reading disability show impaired talker recognition for native and non-native languages. The present study examined whether this relationship is also observed among unimpaired readers. Learning rate and generalization of learning in a talker identification task were examined in average and advanced readers who were tested in both native and non-native language conditions. The results indicate that even among unimpaired readers, phonological competence as captured by reading ability exerts a gradient influence on perceptual learning for talkers' voices.

I Forget What That's Called! Children's Online Processing of Disfluencies Depends on Speaker Knowledge.

Speech disfluencies can convey information to listeners: Adults and children predict that filled pauses (e.g., uhh) will be followed by referents that are difficult to describe or are new to the discourse. In adults, this is driven partly by an understanding that disfluencies reflect processing difficulties. This experiment examined whether 3½-year-olds' use of disfluencies similarly involves inferences about processing difficulty. Forty children were introduced to either a knowledgeable or a forgetful speaker, who then produced fluent and disfluent utterances. Children exposed to the knowledgeable speaker looked preferentially at novel, discourse-new objects during disfluent utterances. However, children who heard the forgetful speaker did not. These results suggest that, like adults, children modify their expectations about the informativeness of disfluencies on a speaker-specific basis.

Language exposure facilitates talker learning prior to language comprehension, even in adults.

Adults show a native language advantage for talker identification, which has been interpreted as evidence that phonological knowledge mediates talker learning. However, infants also show a native language benefit for talker discrimination, suggesting that sensitivity to linguistic structure due to systematic language exposure promotes talker learning, even in the absence of functional phonological knowledge or language comprehension. We tested this hypothesis by comparing two groups of English-monolingual adults on their ability to learn English and French voices. One group resided in Montréal with regular exposure to spoken French; the other resided in Storrs, Connecticut and did not have French exposure. Montréal residents showed faster learning and better retention for the French voices compared to their Storrs-residing peers. These findings demonstrate that systematic exposure to a foreign language bolsters talker learning in that language, expanding the gradient effect of language experience on talker learning to perceptual learning that precedes sentence comprehension.