Infants' vocalizations at 6 months predict their productive vocabulary at one year

How does social contingency facilitate vocabulary development?

Previous research shows that infants of parents who are more likely to engage in socially contingent interactions with them tend to have larger vocabularies. An open question is how social contingency facilitates vocabulary growth. One possibility is that parents who speak in response to their infants more often produce larger amount of language input, which accelerates vocabulary growth. Another possibility is that the simplicity of contingent language input is especially suitable to support early word learning. A third possibility is that more evidence of the communicative nature of language, achieved through frequent contingent responses, helps infants build a link between their own words or vocalizations and others' behaviors. This link may lead to a better understanding of the communicative nature of language and further language advances, including vocabulary growth. To distinguish between these hypotheses, we analyzed the relations between parent-infant interactions when infants were 9 months and their vocabulary size at 12 months, using a naturalistic corpus. Our findings show that the frequency of parents' verbal contingent responses predicts receptive vocabulary size at 12 months and this predictive relation is unlikely to be due to the amount of language input or the simplicity of language within socially contingent interactions. RESEARCH HIGHLIGHTS: Infants of parents who respond to their vocalizations more often during the first year of life tend to have larger vocabularies in the second year. It is an open question what drives the predictive relation between parents' responsiveness and infants' vocabulary; we tested three hypotheses that offer competing explanations. More responsive parents might provide (1) more language input, (2) simpler language input, (3) more evidence of the communicative nature of language (via frequent responses). We find support for the third hypothesis; the frequency of parents' responses predicts infants' vocabularies above and beyond the amount and simplicity of language input.

Associations between urbanization and the home language environment: Evidence from a LENA study in rural and peri-urban China

In low- and middle-income countries, urbanization has spurred the expansion of peri-urban communities, or urban communities of formerly rural residents with low socioeconomic status. The growth of these communities offers researchers an opportunity to measure the associations between the level of urbanization and the home language environment (HLE) among otherwise similar populations. Data were collected in 2019 using Language Environment Analysis observational assessment technology from 158 peri-urban and rural households with Han Chinese children (92 males, 66 females) aged 18-24 months in China. Peri-urban children scored lower than rural children in measures of the HLE and language development. In both samples, child age, gender, maternal employment, and sibling number were positively correlated with the HLE, which was in turn correlated with language development.

Prelinguistic communication complexity predicts expressive language in initial minimally verbal autistic children

BACKGROUND

Prelinguistic communication complexity refers to the use of different communication forms such as eye gaze, gestures and vocalisations and the degree to which these forms are coordinated and how directed to a communication partner. To date, little is known about the relationship between prelinguistic communication complexity and expressive language in minimally verbal autistic children.

AIMS

To test the hypothesis that prelinguistic communication complexity predicts expressive language 12 months later in autistic children and explore whether there are any differences in specific prelinguistic intentional communicative behaviours that are related to later expressive language levels.

METHODS & PROCEDURES

This longitudinal study examined 37 minimally verbal autistic children (29-71 months old). The Communication Complexity Scale (CCS) was used to measure participants' prelinguistic communication behaviours, which were extracted from a semi-structured play interaction at Time 1. The Chinese Communicative Development Inventory (CCDI) was used to examine participants' expressive language at Time 1 and Time 2 (12 months later). According to Time 2 vocabulary size, participants were divided into two groups: Low CCDI, between 0 and 62 words, and High CCDI, more than 100 words. Linear regression was used to examine the relationship between early prelinguistic communication complexity and later expressive language. Binary logistic regression was used to determine which of the early communication behaviours were uniquely significantly related to later expressive language levels.

OUTCOMES & RESULTS

There was a significant positive relationship between prelinguistic communication complexity and expressive language 12 months later, even after controlling for age and concurrent language. Findings revealed a group difference in the frequency of gesture and vocalisation combinations between the Low and High CCDI groups at Time 1. Gesture-vocalisation combinations also predicted better expressive language levels at Time 2.

CONCLUSIONS & IMPLICATIONS

Our findings suggest that it may be beneficial to incorporate different complex communication behaviours into prelinguistic intervention targets for minimally verbal autistic children. The CCS hierarchies can be used as a reference for the intervention goals of minimally verbal autistic children. These findings highlight the importance of targeting gesture and vocalisation combinations when autistic children transition from single prelinguistic communication behaviours to multimodal behaviours.

WHAT THIS PAPER ADDS

What is already known on this subject Children use eye gaze, gestures and vocalisations to communicate with others before they learn spoken language. There is strong evidence suggest that the frequency of prelinguistic communication predicts later linguistic achievements in autistic children. However, less is known about whether prelinguistic communication complexity also predicts later language and which specific behaviours are most predictive of language outcomes. What this study adds Minimally verbal autistic children who exhibit more complex prelinguistic communication behaviours have better expressive language 12 months later. Gestures combined with vocalisations predict better expressive language in minimally verbal autistic children. What are the clinical implications of this work? When identifying intervention targets for minimally verbal autistic children, the clinicians may reference the prelinguistic communication behaviours from the CCS. The gesture and vocalisation combinations are the key behaviours when targets transit from single form to two-form behaviours.

Factors of parental investment in the home language environment in peri-urban China: A mixed methods study

The home language environment is a critical point of investment in early language skills. However, few studies have quantitatively measured the home language environment of low-socioeconomic-status households in non-western settings. This mixed methods study describes the home language environment and early child language skills among households in a low-socioeconomic-status, peri-urban district of Chengdu, China, and identifies factors influencing parental investment in the home language environment. Audio recordings were collected from 81 peri-urban households with children ages 18-24 months and analysed using the Language Environment Analysis (LENATM) system. The Mandarin version of the MacArthur-Bates Communicative Development Inventory was administered to each child's primary caregiver. The quantitative results revealed large variation in home language environments and child language skills among the sample, with relatively low average scores when compared to other Chinese samples. Qualitative interviews with a subset of 31 caregivers revealed that many caregivers face constraints on their knowledge of interactive parenting, compounded, in some households, by time constraints due to work or household responsibilities. The findings indicate a need for increased sources of credible parenting information for peri-urban caregivers of young children to promote investment in the home language environment.

Language Experience during Infancy Predicts White Matter Myelination at Age 2 Years

Parental input is considered a key predictor of language achievement during the first years of life, yet relatively few studies have assessed the effects of parental language input and parent-infant interactions on early brain development. We examined the relationship between measures of parent and child language, obtained from naturalistic home recordings at child ages 6, 10, 14, 18, and 24 months, and estimates of white matter myelination, derived from quantitative MRI at age 2 years (mean = 26.30 months, SD = 1.62, N = 22). Analysis of the white matter focused on dorsal pathways associated with expressive language development and long-term language ability, namely, the left arcuate fasciculus (AF) and superior longitudinal fasciculus (SLF). Frequency of parent-infant conversational turns (CT) uniquely predicted myelin density estimates in both the AF and SLF. Moreover, the effect of CT remained significant while controlling for total adult speech and child speech-related utterances, suggesting a specific role for interactive language experience, rather than simply speech exposure or production. An exploratory analysis of 18 additional tracts, including the right AF and SLF, indicated a high degree of anatomic specificity. Longitudinal analyses of parent and child language variables indicated an effect of CT as early as 6 months of age, as well as an ongoing effect over infancy. Together, these results link parent-infant conversational turns to white matter myelination at age 2 years, and suggest that early, interactive experiences with language uniquely contribute to the development of white matter associated with long-term language ability.SIGNIFICANCE STATEMENT Children's earliest experiences with language are thought to have profound and lasting developmental effects. Recent studies suggest that intervention can increase the quality of parental language input and improve children's learning outcomes. However, important questions remain about the optimal timing of intervention, and the relationship between specific aspects of language experience and brain development. We report that parent-infant turn-taking during home language interactions correlates with myelination of language related white matter pathways through age 2 years. Effects were independent of total speech exposure and infant vocalizations and evident starting at 6 months of age, suggesting that structured language interactions throughout infancy may uniquely support the ongoing development of brain systems critical to long-term language ability.

The importance of deep speech phenotyping for neurodevelopmental and genetic disorders: a conceptual review

Background

Speech is the most common modality through which language is communicated, and delayed, disordered, or absent speech production is a hallmark of many neurodevelopmental and genetic disorders. Yet, speech is not often carefully phenotyped in neurodevelopmental disorders. In this paper, we argue that such deep phenotyping, defined as phenotyping that is specific to speech production and not conflated with language or cognitive ability, is vital if we are to understand how genetic variations affect the brain regions that are associated with spoken language.

Speech is distinct from language, though the two are related behaviorally and share neural substrates. We present a brief taxonomy of developmental speech production disorders, with particular emphasis on the motor speech disorders childhood apraxia of speech (a disorder of motor planning) and childhood dysarthria (a set of disorders of motor execution). We review the history of discoveries concerning the KE family, in whom a hereditary form of communication impairment was identified as childhood apraxia of speech and linked to dysfunction in the FOXP2 gene. The story demonstrates how instrumental deep phenotyping of speech production was in this seminal discovery in the genetics of speech and language. There is considerable overlap between the neural substrates associated with speech production and with FOXP2 expression, suggesting that further genes associated with speech dysfunction will also be expressed in similar brain regions. We then show how a biologically accurate computational model of speech production, in combination with detailed information about speech production in children with developmental disorders, can generate testable hypotheses about the nature, genetics, and neurology of speech disorders.

Conclusions

Though speech and language are distinct, specific types of developmental speech disorder are associated with far-reaching effects on verbal communication in children with neurodevelopmental disorders. Therefore, detailed speech phenotyping, in collaboration with experts on pediatric speech development and disorders, can lead us to a new generation of discoveries about how speech development is affected in genetic disorders.

The maturational gradient of infant vocalizations: Developmental stages and functional modules

Stage models have been influential in characterizing infant vocalizations in the first year of life. These models are basically descriptive and do not explain why certain types of vocal behaviors occur within a particular stage or why successive patterns of vocalization occur. This review paper summarizes and elaborates a theory of Developmental Functional Modules (DFMs) and discusses how maturational gradients in the DFMs explain age typical vocalizations as well as the transitions between successive stages or other static forms. Maturational gradients are based on biological processes that effect the reconfiguration and remodeling of the respiratory, laryngeal, and craniofacial systems during infancy. From a dynamic systems perspective, DFMs are part of a complex system with multiple degrees of freedom that can achieve stable performance with relatively few control variables by relying on principles such as synergies, self-organization, nonlinear performance, and movement variability.