Most deaf children have hearing parents who do not know a sign language at birth, and are at risk of limited language input during early childhood. Studying these children as they learn a sign language has revealed that timing of first-language exposure critically shapes language outcomes. But the input deaf children receive in their first language is not only delayed, it is much more variable than most first language learners, as many learn their first language from parents who are themselves new sign language learners. Much of the research on deaf children learning a sign language has considered the role of parent input using broad strokes, categorizing hearing parents as non-native, poor signers, and deaf parents as native, strong signers. In this study, we deconstruct these categories, and examine how variation in sign language skills among hearing parents might affect children\'s vocabulary acquisition. This study included 44 deaf children between 8- and 60-months-old who were learning ASL and had hearing parents who were also learning ASL. We observed an interactive effect of parent ASL proficiency and age, such that parent ASL proficiency was a significant predictor of child ASL vocabulary size, but not among the infants and toddlers. The proficiency of language models can affect acquisition above and beyond age of acquisition, particularly as children grow. At the same time, the most skilled parents in this sample were not as fluent as \"native\" deaf signers, and yet their children reliably had age-expected ASL vocabularies. Data and reproducible analyses are available at https://osf.io/9ya6h/.

Early in the COVID-19 pandemic, extensive lockdowns interrupted daily routines, including childcare. We asked whether these interruptions, and the inevitable changes in the people with whom children spent their waking hours, caused changes in the languages that children heard. We retrospectively queried parents of young children (0-4 years) in the US about childcare arrangements and exposure to English and non-English languages at four timepoints from February 2020 to September 2021. Despite discontinuity in childcare arrangements, we found that children\'s exposure to English versus other languages remained relatively stable. We also identified demographic variables (child age at pandemic onset, parental proficiency in a non-English language) that consistently predicted exposure to non-English languages. Thus, multilingually-exposed children in this population did not appear to significantly gain or lose the opportunity to hear non-English languages overall. These results provide insight into the experiences of this unique cohort and inform our understanding of how language development can be shaped by complex environmental systems.

Children who receive cochlear implants develop spoken language on a protracted timescale. The home environment facilitates speech-language development, yet it is relatively unknown how the environment differs between children with cochlear implants and typical hearing. We matched eighteen preschoolers with implants (31-65 months) to two groups of children with typical hearing: by chronological age and hearing age. Each child completed a long-form, naturalistic audio recording of their home environment (appx. 16 hours/child; >730 hours of observation) to measure adult speech input, child vocal productivity, and caregiver-child interaction. Results showed that children with cochlear implants and typical hearing were exposed to and engaged in similar amounts of spoken language with caregivers. However, the home environment did not reflect developmental stages as closely for children with implants, or predict their speech outcomes as strongly. Home-based speech-language interventions should focus on the unique input-outcome relationships for this group of children with hearing loss.

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.

Caregivers use a of combination labeling, pointing, object grasping, and gaze to communicate with infants about referents in their environment. By two years of age, children reliably use these referent-oriented cues to communicate and learn. While there is some evidence from lab-based studies that younger infants attend to and use referent-oriented cues during communication, some more naturalistic studies have found that in the first year of life, infants do not robustly leverage these cues during dyadic interactions. The current study examined parent and infant gaze, touching, pointing, and reaching to referents for a wide range of nouns, verbs, adjectives, and other early-learned words during 59 one-hour head-camera recordings sampled from one English-learning infants\' life between 6 and 12 months of age. We found substantial variability across individual words for all cues. Some variability was explained by referent concreteness and the grammatical category of the label. The parent\'s touching of labeled referents increased across months, suggesting that parent-infant-referent interactions may change with development. Future studies should investigate the trajectories of specific types of words and contexts, rather than attempting to discover possibly non-existent universal trajectories of parent and infant referent-oriented behaviors.

During everyday interactions, mothers and infants achieve behavioral synchrony at multiple levels. The ebb-and-flow of mother-infant physical proximity may be a central type of synchrony that establishes a common ground for infant-mother interaction. However, the role of proximity in language exchanges is relatively unstudied, perhaps because structured tasks-the common setup for observing infant-caregiver interactions-establish proximity by design. We videorecorded 100 mothers (U.S. Hispanic N = 50, U.S. Non-Hispanic N = 50) and their 13- to 23-month-old infants during natural activity at home (1-to-2 h per dyad), transcribed mother and infant speech, and coded proximity continuously (i.e., infants and mother within arms reach). In both samples, dyads entered proximity in a bursty temporal pattern, with bouts of proximity interspersed with bouts of physical distance. As hypothesized, Non-Hispanic and Hispanic mothers produced more words and a greater variety of words when within arms reach than out of arms reach. Similarly, infants produced more utterances that contained words when close to mother than when not. However, infants babbled equally often regardless of proximity, generating abundant opportunities to play with sounds. Physical proximity expands opportunities for language exchanges and infants\' communicative word use, although babies accumulate massive practice babbling even when caregivers are not proximal.

Migration is a complex process associated with a range of social, economic, and political reasons. In the U.S., almost one-quarter of the total population of parents are immigrant parents of children ages 0-10. Immigrant parents transmit values from their culture of origin as well as their language to their children. Additionally, they may undergo a process of cultural and psychological change known as acculturation. Research has shown that acculturation can be linked to parenting styles and adolescents\' psychological well-being and behavioral problems. However, little is known about the associations among immigrant parents\' acculturation, their home language and literacy practices, and their bilingual children\'s language skills. This study explores the relationships among reasons for migration, parental acculturation, home language and literacy practices, and child expressive vocabulary in English and their heritage language (HL). A group of 190 Spanish-English (N = 66) and Chinese-English (N = 124) dual language learners (DLLs) (mean age = 48.98 months) and their Chinese and Mexican parents (mean age of migration = 18.57 and 21.38 years old respectively participated. Frequency counts revealed that Mexican American families migrated to the U.S. mostly for multiple reasons, including joining family members, getting married, and looking for better education or job opportunities, whereas most Chinese American families migrated for family reasons only. Path analysis models showed that, for both cultural groups, language input in Spanish and Chinese mediated the relationship between parents\' cultural orientations and DLLs\' HL expressive vocabulary. These findings emphasize that despite the heterogeneity of immigrant families and the variability in DLLs\' vocabulary skills in preschool, there exist some similarities across immigrant parents and bilingual children. A deeper understanding of acculturation practices and home language use can help educators better support children from diverse backgrounds and promote cultural awareness and sensitivity in the classroom.

Learning a language is, at its core, a process of noticing patterns in the language input surrounding the learner. Although many of these language patterns are complex and difficult for adult speakers/signers to recognize, infants are able to find and learn them from the youngest age, without explicit instruction. However, this impressive feat is dependent on children\'s early access to ample and well-formed input that displays the regular patterns of natural language. Such input is far from guaranteed for the great majority of deaf and hard of hearing (DHH) children, leading to well-documented difficulties and delays in linguistic development. Efforts to remedy this situation have focused disproportionately on amplifying DHH children\'s hearing levels, often through cochlear implants, as young as possible to facilitate early access to spoken language. Given the time required for cochlear implantation, its lack of guaranteed success, and the critical importance of exposing infants to quality language input as early as possible, a bimodal bilingual approach can optimize DHH infants\' chances for on-time language development by providing them with both spoken and signed language input from the start. This paper addresses the common claim that signing with DHH children renders the task of learning spoken language more difficult, leading to delays and inferior language development, compared to DHH children in oral-only environments. That viewpoint has most recently been articulated by Geers et al. (2017a), which I will discuss as a representative of the many studies promoting an oral-only approach. Contrary to their claims that signing degrades the language input available to DHH children, recent research has demonstrated that the formidable pattern-finding skills of newborn infants extends to linguistic cues in both the spoken and signed modalities, and that the additional challenge of simultaneously acquiring two languages is offset by important \"bilingual advantages.\" Of course, securing early access to high quality signed input for DHH children from hearing families requires considerable effort, especially since most hearing parents are still novice signers. This paper closes with some suggestions for how to address this challenge through partnerships between linguistics researchers and early intervention programs to support family-centered bimodal bilingual development for DHH children.

The language environment to which children are exposed has an impact on later language abilities as well as on brain development; however, it is unclear how early such impacts emerge. This study investigates the effects of children\'s early language environment and socioeconomic status (SES) on brain structure in infancy at 6 and 30 months of age (both sexes included). We used magnetic resonance imaging to quantify concentrations of myelin in specific fiber tracts in the brain. Our central question was whether Language Environment Analysis (LENA) measures from in-home recording devices and SES measures of maternal education predicted myelin concentrations over the course of development. Results indicate that 30-month-old children exposed to larger amounts of in-home adult input showed more myelination in the white matter tracts most associated with language. Right hemisphere regions also show an association with SES, with older children from more highly educated mothers and exposed to more adult input, showing greater myelin concentrations in language-related areas. We discuss these results in relation to the current literature and implications for future research.SIGNIFICANCE STATEMENT This is the first study to look at how brain myelination is impacted by language input and socioeconomic status early in development. We find robust relationships of both factors in language-related brain areas at 30 months of age.

The Language ENvironment Analysis system (LENA) records children\'s language environment and provides an automatic estimate of adult-child conversational turn count (CTC) by automatically identifying adult and child speech in close temporal proximity. To assess the reliability of this measure, we examine correlation and agreement between LENA\'s CTC estimates and manual measurement of adult-child turn-taking in two corpora collected in the USA: a bilingual corpus of Spanish-English-speaking families with infants between 4 and 22 months (n = 37), and a corpus of monolingual families with English-speaking 5-year-olds (n = 56). In each corpus for each child, 100 30-second segments were extracted from daylong recordings in two ways, yielding a total of 9300 minutes of manually annotated audio. LENA\'s CTC estimate for the same segments was obtained through the LENA software. The two measures of CTC had low correlations for the segments from the monolingual 5-year-olds sampled in both ways, and somewhat higher correlations for the bilingual samples. LENA substantially overestimated CTC on average, relative to manual measurement, for three out of four analysis conditions, and limits of agreement were wide in all cases. Segment-level analyses demonstrated that accidental contiguity had the largest individual impact on LENA\'s average CTC error, affecting 12-17% of analyzed segments. Other factors significantly contributing to CTC error were speech from other children, presence of multiple adults, and presence of electronic media. These results indicate wide discrepancies between LENA\'s CTC estimates and manual CTCs, and call into question the comparability of LENA\'s CTC measure across participants, conditions, and developmental time points.