Language Exposure and Brain Myelination in Early Development.

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.

Parentese in infancy predicts 5-year language complexity and conversational turns.

Parental input is considered a key predictor of language achievement during the first years of life, yet relatively few studies have assessed its effects on longer-term outcomes. We assess the effects of parental quantity of speech, use of parentese (the acoustically exaggerated, clear, and higher-pitched speech), and turn-taking in infancy, on child language at 5 years. Using a longitudinal dataset of daylong LENA recordings collected with the same group of English-speaking infants (N=44) at 6, 10, 14, 18, 24 months and then again at 5 years, we demonstrate that parents' consistent (defined as stable and high) use of parentese in infancy was a potent predictor of lexical diversity, mean length of utterance, and frequency of conversational turn-taking between children and adults at Kindergarten entry. Together, these findings highlight the potential importance of a high-quality language learning environment in infancy for success at the start of formal schooling.

The everyday speech environments of preschoolers with and without cochlear implants.

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.

A comparison of automatic and manual measures of turn-taking in monolingual and bilingual contexts.

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.

"Go, go, go!" Mothers' verbs align with infants' locomotion.

Caregivers often tailor their language to infants' ongoing actions (e.g., "are you stacking the blocks?"). When infants develop new motor skills, do caregivers show concomitant changes in their language input? We tested whether the use of verbs that refer to locomotor actions (e.g., "come," "bring," "walk") differed for mothers of 13-month-old crawling (N = 16) and walking infants (N = 16), and mothers of 18-month-old experienced walkers (N = 16). Mothers directed twice as many locomotor verbs to walkers compared to same-age crawlers, but mothers' locomotor verbs were similar for younger and older walkers. In real-time, mothers' use of locomotor verbs was dense when infants were locomoting, and sparse when infants were stationary, regardless of infants' crawler/walker status. Consequently, infants who spent more time in motion received more locomotor verbs compared to infants who moved less frequently. Findings indicate that infants' motor skills guide their in-the-moment behaviors, which in turn shape the language they receive from caregivers. RESEARCH HIGHLIGHTS: Infants' motor skills guide their in-the-moment behaviors, which in turn shape the language they receive from caregivers. Mothers directed more frequent and diverse verbs that referenced locomotion (e.g., "come," "go," "bring") to walking infants compared to same-aged crawling infants. Mothers' locomotor verbs were temporally dense when infants locomoted and sparse when infants were stationary, regardless of whether infants could walk or only crawl.

Parent coaching from 6 to 18 months improves child language outcomes through 30 months of age.

Interventions focused on the home language environment have been shown to improve a number of child language outcomes in the first years of life. However, data on the longer-term effects of the intervention are still somewhat limited. The current study examines child vocabulary and complex speech outcomes (N = 59) during the year following completion of a parent-coaching intervention, which was previously found to increase the quantity of parent-child conversational turns and to improve child language outcomes through 18 months of age. Measures of parental language input, child speech output, and parent-child conversational turn-taking were manually coded from naturalistic home recordings (Language Environment Analysis System, LENA) at regular 4-month intervals when children were 6- to 24-months old. Child language skills were assessed using the MacArthur-Bates Communicative Development Inventory (CDI) at four time-points following the final intervention session (at 18, 24, 27, and 30 months). Vocabulary size and growth from 18 to 30 months was greater in the intervention group, even after accounting for differences in child language ability during the intervention period. The intervention group also scored higher on measures of speech length and grammatical complexity, and these effects were mediated by 18-month vocabulary. Intervention was associated with increased parent-child conversational turn-taking in home recordings at 14 months, and mediation analysis suggested that 14-month conversational turn-taking accounted for intervention-related differences in subsequent vocabulary. Together, the results suggest enduring, positive effects of parental language intervention and underscore the importance of interactive, conversational language experience during the first 2 years of life. RESEARCH HIGHLIGHTS: Parent coaching was provided as part of a home language intervention when children were 6-18 months of age. Naturalistic home language recordings showed increased parent-child conversational turn-taking in the intervention group at 14 months of age. Measures of productive vocabulary and complex speech indicated more advanced expressive language skills in the intervention group through 30 months of age, a full year after the final intervention session. Conversational turn-taking at 14 months predicted subsequent child vocabulary and accounted for differences in vocabulary size across the intervention and control groups.

Spanish-English bilingual toddlers' vocabulary skills: The role of caregiver language input and warmth.

There is a well-documented link between bilingual language development and the relative amounts of exposure to each language. Less is known about the role of quality indicators of caregiver-child interactions in bilingual homes, including caregiver input diversity, warmth and sensitivity. This longitudinal study examines the relation between caregiver input (lexical diversity, amount), warmth and sensitivity and bilingual toddlers' subsequent vocabulary outcomes. We video-recorded caregiver-child interactions in Spanish-English Latino homes when toddlers (n = 47) were 18 months of age (M = 18.32 months; SD = 1.02 months). At the 24-month follow-up, we measured children's vocabulary as total vocabulary (English, Spanish combined) as well as within language (Spanish, English). Results revealed that Spanish lexical diversity exposure at 18 months from caregivers was positively associated with children's Spanish and total vocabulary scores at 24 months, while English lexical diversity was positively associated with children's English scores; lexical diversity and amount were highly correlated. Additionally, caregivers' warmth was positively associated with children's Spanish, English and total vocabulary scores. Together, these factors accounted for substantial variance (30-40%) in vocabulary outcomes. Notably, caregiver input accounted for more variance in single language outcomes than did caregiver warmth, whereas caregiver warmth uniquely accounted for more variance in total vocabulary scores. Our findings extend prior research findings by suggesting that children's dual language development may depend on their exposure to a diverse set of words, not only amount of language exposure, as well as warm interactions with caregivers. A video abstract of this article can be viewed at https://youtu.be/q1V_7fz5wog HIGHLIGHTS: Video-recorded observations of caregiver-child interactions revealed warmth and high sensitivity from Latino caregivers. Linguistically-detailed analyses of caregiver input revealed wide variation in the diversity of Spanish and English directed at 18-month-old bilingual toddlers. Bilingual toddlers' vocabulary (single language, total) was positively associated with caregivers' diverse input and warmth, thus extending prior findings on bilinguals' amount of language exposure. Findings suggest that caregivers' lexical diversity explains more variance in bilingual toddlers' single language outcomes, whereas warmth explains more variance in total vocabulary scores.

Caregiver object labels within supported and coordinated joint engagement during interaction with toddlers at elevated and typical likelihood of autism.

BACKGROUND: Early in development, caregivers' object labelling contributes to children's word learning. Language development is a bi-directional process, and differences in joint engagement (JE) and language among children with developmental disabilities such as autism spectrum disorder (ASD) may provide caregivers varying contexts and opportunities to provide object labels. However, potential variation in caregivers' production of object labels and its relation to language development remain relatively unexplored among toddlers with ASD. AIMS: This study characterized the structural and functional features of object labels produced by parents of children with typical (TL) or elevated likelihood (EL) of ASD during naturalistic toy play. We examined features of object labels within two JE contexts, supported and coordinated JE, which are differentiated by a child's use of eye contact, as well as their relations with concurrent and future child language skills. METHODS & PROCEDURES: The present study included 55 (TL = 12, EL = 43) children who completed a naturalistic parent-child interaction in the home at 18 months of age. Children's expressive and receptive language was assessed at 18, 24 and 36 months. At 36 months, EL children were assessed for ASD and classified as either EL-No Diagnosis, EL-Language Delay or EL-ASD. Videos of interactions were divided into discrete engagement states, including supported and coordinated JE. All parent speech was transcribed and coded to capture structural (types, tokens, mean length of utterance (MLU), sentence position) and functional (follow-in comments, directives, lead-in labels) features of object labels as well as parent prompts for the child to produce a label. OUTCOMES & RESULTS: Parents of toddlers across outcome groups labelled objects at similar rates within each engagement state. However, parents of EL-ASD children provided the lowest rates of prompts for labels in supported JE and the highest rate of labels as the final word of an utterance (sentence-final position) in coordinated JE. Additionally, parent prompts in supported JE were related to concurrent child expressive language. Labels in sentence-final position were positively related to later language outcome when delivered in supported JE but were associated with poorer language outcomes when delivered in coordinated JE. CONCLUSIONS & IMPLICATIONS: Subtle differences in parent object labels across outcome groups demonstrate the role that child language and social engagement can play in influencing parent input and the cascading impact of this input on language development. WHAT THIS PAPER ADDS: What is already known on this subject Variations in caregiver object labelling can impact child language development. However, child characteristics such as language ability also actively shape the input caregivers provide, demonstrating the bi-directionality of language development. What this paper adds to existing knowledge The present study demonstrates that characteristics of the engagement context in which a label is delivered may be important for understanding how object labelling relates to child language acquisition and whether this relation varies for children who face challenges in language learning. What are the potential or actual clinical implications of this work? As child differences in social engagement emerge, parents may be more attuned to moments their children are engaging with eye contact. Caregiver-mediated interventions might consider strategies that guide caregivers in recognizing engagement without eye contact as a similarly meaningful opportunity for learning and encourage the use of rich input within these moments.

Teletherapy, AAC & COVID-19: the experiences of speech language pathologists providing teletherapy during a global pandemic.

The COVID-19 pandemic required many speech-language pathologists (SLPs) to transition to teletherapy service delivery. This study was designed to explore the experiences and perceptions of SLPs who made this transition with children with disabilities who used aided augmentative and alternative communication (AAC). Semi-structured interviews were conducted virtually with 10 SLPs who provided regular teletherapy services to children who used AAC during but not before the pandemic. Interview transcripts were analyzed thematically using immersion, reduction, and constant comparison to understand SLP experiences and perceptions individually and across the group. Results reveal that despite the challenges faced transitioning to teletherapy, there were benefits. Furthermore, many of the participating SLPs developed successful strategies and solutions for the challenges they faced. Participants in this study highlighted the unique and important role that caregivers and parents played in the success of the teletherapy they provided. This study suggests that SLPs, caregivers, and children demonstrated resilience in the face of a large-scale, unforeseen change. SLPs consistently reported the ability to maintain continuity of care during a stressful transition period, while meeting the unique needs of the children who used AAC they served.

Rethinking the phonetics of baby-talk: Differences across Canada and Vanuatu in the articulation of mothers' speech to infants.

Infant-directed speech (IDS) is phonetically distinct from adult-directed speech (ADS): It is typically considered to have special prosody-like higher pitch and slower speaking rates-as well as unique speech sound properties, for example, more breathy, hyperarticulated, and/or variable consonant and vowel articulation. These phonetic features are widely observed in the IDS of caregivers from urbanized contexts who speak a handful of very well-researched languages. Yet studies with more diverse socio-cultural and linguistic samples show that this "typical" IDS prosody is not consistently observed across cultures. We extended cross-cultural work by examining IDS speech segment articulation, which-like prosody-is also thought to be a characteristic phonetic feature of IDS that might aid speech and language development. Here we asked whether IDS vowels have different articulatory features compared to ADS vowels in two distinct linguistic and socio-cultural contexts: urban English-speaking Canadian mothers, and rural Lenakel- and Southwest Tanna-speaking ni-Vanuatu mothers (n = 57, 20-46 years of age). Replicating prior work, Canadian mothers had more variable vowels in IDS compared to ADS, but also did not show clear register differences for breathiness or hyperarticulation. Vowels spoken by ni-Vanuatu mothers showed very distinct articulatory tendencies, using less variable (and less breathy) IDS vowels. Along with other work showing diversity in IDS phonetics across populations, this paper suggests that any understanding of how IDS might aid speech and language development are best examined through a culturally- and linguistically-specific lens.

Language input to infants of different socioeconomic statuses: A quantitative meta-analysis.

For the past 25 years, researchers have investigated language input to children from high- and low-socioeconomic status (SES) families. Hart and Risley first reported a "30 Million Word Gap" between high-SES and low-SES children. More recent studies have challenged the size or even existence of this gap. The present study is a quantitative meta-analysis on socioeconomic differences in language input to young children, which aims to systematically integrate decades of research on this topic. We analyzed 19 studies and found a significant effect of SES on language input quantity. However, this effect was moderated by the type of language included in language quantity measures: studies that include only child-directed speech in their language measures find a large SES difference, while studies that include all speech in a child's environment find no effect of SES. These results support recent work suggesting that methodological decisions can affect researchers' estimates of the "word gap." Overall, we find that young children from low-SES homes heard less child-directed speech than children from mid- to high-SES homes, though this difference was much smaller than Hart & Risley's "30 Million Word Gap." Finally, we underscore the need for more cross-cultural work on language development and the forces that may contribute to it, highlighting the opportunity for better integration of observational, experimental, and intervention-based approaches.

Infants' object interactions are long and complex during everyday joint engagement.

As infants interact with the object world, they generate rich information about object properties and functions. Much of infant learning unfolds in the presence of caregivers, who talk about and act on the objects of infant play. Does mother joint engagement correspond to real-time changes in the complexity and duration of infant object interactions? We observed 38 mothers and their first-born infants (cross-sectional, 13, 18, and 23 months) during 2 h of everyday activity as infants freely navigated their home environments. Behavioral coding explored thousands of infant object interactions within and outside mother joint engagement. Object interactions involving exclusively simple play were shorter than complex play bouts. Critically, mothers' multimodal input (i.e., touching/gesturing toward and talking about the focal object) corresponded with more complex and longer play bouts than when mothers provided no input. Bouts involving complex play and multimodal input lasted 7.5 times longer than simple play bouts absent mother input. Moreover, "action-orienting talk" (e.g., "Twist it", "Feed dolly"), rather than talk per se, corresponded with longer bout duration and complexity. Notably, the association between joint engagement and play duration was not a function of mothers having more time to join. Analyses that eliminated short infant bouts and considered the timing of mothers' behaviors confirmed that mother input "extended" the duration of play bouts. As infants actively explore their environments, their object interactions change moment to moment in the presence of mothers' multimodal engagement.

Multilingual toddlers' vocabulary development in two languages: Comparing bilinguals and trilinguals.

Many children grow up hearing multiple languages, learning words in each. How does the number of languages being learned affect multilinguals' vocabulary development? In a pre-registered study, we compared productive vocabularies of bilingual (n = 170) and trilingual (n = 20) toddlers aged 17-33 months growing up in a bilingual community where both French and English are spoken. We hypothesized that because trilinguals have reduced input in French and English due to time spent hearing their third language, they would have smaller French-English vocabulary sizes than bilinguals. Trilinguals produced on average 2/3 of the number of words in these languages that bilinguals did: however, this difference was not statistically robust due to large levels of variability. Follow-up analyses did, however, indicate a relationship between input quantity and vocabulary size. Our results indicate that similar factors contribute to vocabulary development across toddlers regardless of the number of languages being acquired.

Unique contribution of shared book reading on adult-child language interaction.

Researchers agree that early literacy activities, like book sharing and parent-child play, are important for stimulating language development. We hypothesize that book sharing is most powerful because it elicits more interactive talk in young children than other activities. Parents of 43 infants (9-18 months) made two daylong audio recordings using the LENA system. We compared a typical day, with spontaneous occurring activities, with an instructed day when caregivers were prompted to do book reading and toy play. Book sharing resulted in a combination of more parent talk, child talk, and interactions than other language activities. Research context did not influence outcomes: no differences were found in language use between the spontaneous and the instructed activities. Overall it seems clear that even with infants shared reading is a strong unique stimulator of language use from parent and child.

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.

Physiological arousal and observed behaviour in parent-child interactions involving young children with Down syndrome.

BACKGROUND: Parents of children with Down syndrome (DS) play an important role in their child's development. Physiological measures, such as electrodermal activity (EDA), can shed light on parent-child relations beyond the behavioural level. The goals of the current study were to assess the feasibility of collecting EDA data in preschool age children with DS, examine the association between parent and child EDA during play-based interactions, and investigate the relation between parent and child EDA and observed parent behaviours. METHOD: Two parents in 15 families participated in dyadic free play interactions with their child with DS (i.e., 15 mother-child and 15 father-child interactions). The children with DS (aged 24-61 months) and both of their parents wore multisensory wristbands measuring EDA. Parent behaviours were coded as requests for behavioural complies, requests for verbal complies, or comments. RESULTS: Usable EDA data were collected for 13/15 children and 11/15 mothers during the mother-child interactions and 14/15 children and 12/15 fathers during the father-child interactions. Parent and child EDA variability was significantly positively related for father-child but not mother-child dyads. Maternal use of requests for behavioural complies was positively related to child EDA variability. CONCLUSIONS: The collection of EDA data through wristbands worn by young children with DS during early parent-child interactions was feasible. Preliminary findings indicated that some aspects of parent and child physiology in DS may be related in different ways for mother-child and father-child dyads.

Do, say, learn: the functions of mothers' speech to infants.

We examined the functions of mothers' speech to infants during two tasks - book-sharing and bead-stringing - in low-income, ethnically diverse families. Mexican, Dominican, and African American mothers and their infants were video-recorded sharing wordless books and toy beads in the home when infants were aged 1;2 and 2;0. Mothers' utterances were classified into seven categories (labels/descriptions, emotion/state language, attention directives, action directives, prohibitions, questions, and vocal elicitations) which were grouped into three broad language functions: referential language, regulatory language, and vocalization prompts. Mothers' ethnicity, years of education, years living in the United States, and infant sex and age related to mothers' language functions. Dominican and Mexican mothers were more likely to use regulatory language than were African American mothers, and African American mothers were more likely to use vocalization prompts than were Latina mothers. Vocalization prompts and referential language increased with mothers' education and Latina mothers' years living in the United States. Finally, mothers of boys used more regulatory language than did mothers of girls. Socio-cultural and developmental contexts shape the pragmatics of mothers' language to infants.

Child, family, and school factors in bilingual preschoolers' vocabulary development in heritage languages.

Child characteristics, family factors, and preschool factors are all found to affect the rate of bilingual children's vocabulary development in heritage language (HL). However, what remains unknown is the relative importance of these three sets of factors in HL vocabulary growth. The current study explored the complex issue with 457 Singaporean preschool children who are speaking either Mandarin, Malay, or Tamil as their HL. A series of internal factors (e.g., non-verbal intelligence) and external factors (e.g., maternal educational level) were used to predict children's HL vocabulary growth over a year at preschool with linear mixed effects models.The results demonstrated that external factors (i.e., family and preschool factors) are relatively more important than child characteristics in enhancing bilingual children's HL vocabulary growth. Specifically, children's language input quantity (i.e., home language dominance), input quality (e.g., number of books in HL), and HL input quantity at school (i.e., the time between two waves of tests at preschool) predict the participants' HL vocabulary growth, with initial vocabulary controlled. The relative importance of external factors in bilingual children's HL vocabulary development is attributed to the general bilingual setting in Singapore, where HL is taken as a subject to learn at preschool and children have fairly limited exposure to HL in general. The limited amount of input might not suffice to trigger the full expression of internal resources. Our findings suggest the crucial roles that caregivers and preschools play in early HL education, and the necessity of more parental involvement in early HL learning in particular.

Parents' early book reading to children: Relation to children's later language and literacy outcomes controlling for other parent language input.

It is widely believed that reading to preschool children promotes their language and literacy skills. Yet, whether early parent-child book reading is an index of generally rich linguistic input or a unique predictor of later outcomes remains unclear. To address this question, we asked whether naturally occurring parent-child book reading interactions between 1 and 2.5 years-of-age predict elementary school language and literacy outcomes, controlling for the quantity of other talk parents provide their children, family socioeconomic status, and children's own early language skill. We find that the quantity of parent-child book reading interactions predicts children's later receptive vocabulary, reading comprehension, and internal motivation to read (but not decoding, external motivation to read, or math skill), controlling for these other factors. Importantly, we also find that parent language that occurs during book reading interactions is more sophisticated than parent language outside book reading interactions in terms of vocabulary diversity and syntactic complexity.

Maternal discourse continuity and infants' actions organize 12-month-olds' language exposure during object play.

Infant language learning depends on the distribution of co-occurrences within language-between words and other words-and between language content and events in the world. Yet infant-directed speech is not limited to words that refer to perceivable objects and actions. Rather, caregivers' utterances contain a range of syntactic forms and expressions with diverse attentional, regulatory, social, and referential functions. We conducted a distributional analysis of linguistic content types at the utterance level, and demonstrated that a wide range of content types in maternal speech can be distinguished by their distribution in sequences of utterances and by their patterns of co-occurrence with infants' actions. We observed free-play sessions of 38 12-month-old infants and their mothers, annotated maternal utterances for 10 content types, and coded infants' gaze target and object handling. Results show that all content types tended to repeat in consecutive utterances, whereas preferred transitions between different content types reflected sequences from attention-capturing to directing and then descriptive utterances. Specific content types were associated with infants' engagement with objects (declaratives, descriptions, object names), with disengagement from objects (talk about attention, infant's name), and with infants' gaze at the mother (affirmations). We discuss how structured discourse might facilitate language acquisition by making speech input more predictable and/or by providing clues about high-level form-function mappings.