Infant-adult vocal interaction dynamics depend on infant vocal type, child-directedness of adult speech, and timeframe

Conversation Initiation in Families With a Toddler Who Is Deaf or Hard of Hearing

PURPOSE

The purpose of this work is to describe the conversation initiation rates in families of toddlers who are deaf and hard of hearing (DHH) as compared to those with typical development.

METHOD

Analysis of daylong acoustic recordings was used to describe the conversational dynamics in 78 families, comprising 51 families with a DHH toddler (23 boys, 28 girls) and 27 families with a typically developing (TD) toddler (16 boys, 11 girls). Number of conversational initiations was the primary variable of interest to describe conversational dynamics within families.

RESULTS

Results of this study suggest that toddlers' conversation initiation rate does not differ by the sex or the hearing status of the child; however, mothers initiated conversations at a higher rate than fathers in both the DHH and TD groups.

CONCLUSIONS

Exploring conversation initiation provides a window into the broader development of conversational dynamics that may influence the course of language development in children, especially those with or at risk for a communication disorder. Results indicate that there was no difference in conversation initiation rate between families with DHH toddlers and families of TD toddlers, suggesting that this aspect of conversational dynamics is not influenced by pediatric hearing loss.

Acoustic features of vocalizations in typically developing and autistic infants in the first year

BACKGROUND

We describe acoustic patterns across the five most prominent vocal types in typically developing infants (TD) and compare them with patterns in infants who develop autism (ASD) or a developmental disability (DD) not related to autism. Infant-directed speech (IDS) is a potentially important influence on such vocal acoustic patterns. Both acoustic patterns and effects of IDS are important for understanding the earliest origins of communication disorders.

AIMS

To compare duration, pitch and loudness of infant vocalizations for three groups of infants (TD, ASD, DD) in circumstances with high or low amounts of IDS.

METHODS AND PROCEDURES

Two five-minute segments from each of 1259 all-day recordings across the first year were coded and acoustically analyzed for three groups of infants (130 TD, 44 ASD, 21 DD). Duration, mean fundamental frequency, and root mean square amplitude were determined for >162,000 infant utterances.

OUTCOMES AND RESULTS

Cries were longest and loudest, and vowel-like sounds were shortest of the five vocal types in all groups. TD infants showed significant alterations in vocal acoustics during periods of high IDS.

CONCLUSIONS AND IMPLICATIONS

Strong similarities in acoustic patterns occurred across the three groups, but only the TD group showed significant acoustic effects of IDS.

Toddler negative affectivity and effortful control: Relations with parent-toddler conversation engagement and indirect effects on language

Evidence that early parent-child conversation supports early language development suggests a need to understand factors that account for individual differences in parent-child conversation engagement. Whereas most studies focus on demographic factors, we investigated the role of toddler temperament in a longitudinal study of 120 economically strained families. Specifically, we investigated the degree to which toddlers' negative affectivity and effortful control, considered together as a composite reflecting challenging temperament, accounted for variability in parent-toddler conversation engagement, and whether the frequency of that engagement mediated associations between toddler temperament and toddler expressive language skills. Toddler challenging temperament (i.e., high negative affectivity and low effortful control) and parent-toddler conversation engagement were measured at 18 and 30 months. Toddler expressive language skills were measured at 18, 24, and 36 months. As expected, a path model indicated inverse relations between toddler challenging temperament and concurrent parent-toddler conversation engagement at both 18 and 30 months. Unexpectedly, there were no direct associations between toddler challenging temperament and toddler expressive language skills either concurrently or longitudinally. However, we found indirect effects of toddler challenging temperament on later toddler expressive language skills via parent-toddler conversation engagement. Findings highlight the importance of considering toddler temperamental characteristics in addition to family demographics as important factors that account for variability in parent-toddler conversation engagement.

Hamrick L, Marklund E, Kalashnikova M, Guez A, Casillas M, Benetti L, van Alphen P, Cristia A. Everyday language input and production in 1,001 children from six continents

Language is a universal human ability, acquired readily by young children, who otherwise struggle with many basics of survival. And yet, language ability is variable across individuals. Naturalistic and experimental observations suggest that children's linguistic skills vary with factors like socioeconomic status and children's gender. But which factors really influence children's day-to-day language use? Here, we leverage speech technology in a big-data approach to report on a unique cross-cultural and diverse data set: >2,500 d-long, child-centered audio-recordings of 1,001 2- to 48-mo-olds from 12 countries spanning six continents across urban, farmer-forager, and subsistence-farming contexts. As expected, age and language-relevant clinical risks and diagnoses predicted how much speech (and speech-like vocalization) children produced. Critically, so too did adult talk in children's environments: Children who heard more talk from adults produced more speech. In contrast to previous conclusions based on more limited sampling methods and a different set of language proxies, socioeconomic status (operationalized as maternal education) was not significantly associated with children's productions over the first 4 y of life, and neither were gender or multilingualism. These findings from large-scale naturalistic data advance our understanding of which factors are robust predictors of variability in the speech behaviors of young learners in a wide range of everyday contexts.

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.

Parental verbal responsiveness to infant vocalizations from 9 to 14 months of age

Parental communication styles and language usage may undergo changes during the course of child development, exhibiting variations across language backgrounds and cultures. This study aimed to explore how infant-parent interactions within Korean-speaking environments evolve over time through meticulous coding of day-long home audio recordings. The study examined whether the ratio and types of parental verbal responses vary based on infants' age and vocalization types. A total of 16 infants and their parents participated in all-day home recordings using the Language Environment Analysis (LENA) system. The recordings were conducted in two rounds per family when the infants were aged 9-11 months and 12-14 months, with a three-month gap between each round. The frequency and types of infant vocalizations were analyzed and the contingency and types of parental verbal responsiveness were determined based on semantic and phonetic connection, as well as temporal appropriateness. The results showed that parents did not verbally respond to approximately 50 % of the infant vocalizations in the natural home environment. However, parents' lack of verbal responses decreased significantly, and their contingent responses increased significantly with infant age. Parents were also not selectively responsive to infants' canonical vocalizations over non-canonical vocalizations. Nevertheless, parents demonstrated a higher frequency of responses that were not only linguistically meaningful but also socially appropriate and contextually relevant to infants' vocalizations as infants developed, which may play a significant role in scaffolding speech and language development.

Early antecedents of emotion differentiation and regulation: Experience tunes the appraisal thresholds of emotional development in infancy

In this review, we synthesize evidence to highlight cognitive appraisal as an important developmental antecedent of individual differences in emotion differentiation and adept emotion regulation. Emotion differentiation is the degree to which emotions are experienced in a nuanced or "granular" way-as specific and separable phenomena. More extensive differentiation is related to positive wellbeing and has emerged as a correlate of emotion regulation skill among adults. We argue that the cognitive appraisal processes that underlie these facets of emotional development are instantiated early in the first year of life and tuned by environmental input and experience. Powerful socializing input in the form of caregivers' contingent and selective responding to infants' emotional signals carves and calibrates the infant's appraisal thresholds for what in their world ought to be noticed, deemed as important or personally meaningful, and responded to (whether and how). These appraisal thresholds are thus unique to the individual child despite the ubiquity of the appraisal process in emotional responding. This appraisal infrastructure, while plastic and continually informed by experience across the lifespan, likely tunes subsequent emotion differentiation, with implications for children's emotion regulatory choices and skills. We end with recommendations for future research in this area, including the urgent need for developmental emotion science to investigate the diverse sociocultural contexts in which children's cognitive appraisals, differentiation of emotions, and regulatory responses are being built across childhood.

Child language and autism diagnosis impact hierarchical temporal structure of parent-child vocal interactions in early childhood

Timing is critical to successful social interactions. The temporal structure of dyadic vocal interactions emerges from the rhythm, timing, and frequency of each individuals' vocalizations and reflects how the dyad dynamically organizes and adapts during an interaction. This study investigated the temporal structure of vocal interactions longitudinally in parent-child dyads of typically developing (TD) infants (n = 49; 9-18 months; 48% male) and toddlers with ASD (n = 23; 27.2 ± 5.0 months; 91.3% male) to identify how developing language and social skills impact the temporal dynamics of the interaction. Acoustic hierarchical temporal structure (HTS), a measure of the nested clustering of acoustic events across multiple timescales, was measured in free play interactions using Allan Factor. HTS reflects a signal's temporal complexity and variability, with greater HTS indicating reduced flexibility of the dyadic system. Child expressive language significantly predicted HTS (ß = -0.2) longitudinally across TD infants, with greater dyadic HTS associated with lower child language skills. ASD dyads exhibited greater HTS (i.e., more rigid temporal structure) than nonverbal matched (d = 0.41) and expressive language matched TD dyads (d = 0.28). Increased HTS in ASD dyads occurred at timescales >1 s, suggesting greater structuring of pragmatic aspects of interaction. Results provide a new window into how language development and social reciprocity serve as constraints to shape parent-child interaction dynamics and showcase a novel automated approach to characterizing vocal interactions across multiple timescales during early childhood.

Conversation Initiation of Mothers, Fathers, and Toddlers in their Natural Home Environment

In a conversational exchange, interlocutors use social cues including conversational turn-taking to communicate. There has been attention in the literature concerning how mothers, fathers, boys, and girls converse with each other, and in particular who initiates a conversation. Better understanding of conversational dynamics may deepen our understanding of social roles, speech and language development, and individual language variability. Here we use large-scale automatic analysis of 186 naturalistic daylong acoustic recordings to examine the conversational dynamics of 26 families with children about 30 months of age to better understand communication roles. Families included 15 with boys and 11 with girls. There was no difference in conversation initiation rate by child sex, but children initiated more conversations than mothers, and mothers initiated more than fathers. Results support developmental theories of the different and variable roles that interlocutors play in a social context.

Perspectives on the origin of language: Infants vocalize most during independent vocal play but produce their most speech-like vocalizations during turn taking

A growing body of research emphasizes both endogenous and social motivations in human vocal development. Our own efforts seek to establish an evolutionary and developmental perspective on the existence and usage of speech-like vocalizations ("protophones") in the first year of life. We evaluated the relative occurrence of protophones in 40 typically developing infants across the second-half year based on longitudinal all-day recordings. Infants showed strong endogenous motivation to vocalize, producing vastly more protophones during independent vocal exploration and play than during vocal turn taking. Both periods of vocal play and periods of turn-taking corresponded to elevated levels of the most advanced protophones (canonical babbling) relative to periods without vocal play or without turn-taking. Notably, periods of turn taking showed even more canonical babbling than periods of vocal play. We conclude that endogenous motivation drives infants' tendencies to explore and display a great number of speech-like vocalizations, but that social interaction drives the production of the most speech-like forms. The results inform our previously published proposal that the human infant has been naturally selected to explore protophone production and that the exploratory inclination in our hominin ancestors formed a foundation for language.

Efficient Estimation of Children's Language Exposure in Two Bilingual Communities

Purpose The language that children hear early in life is associated with their speech-language outcomes. This line of research relies on naturalistic observations of children's language input, often captured with daylong audio recordings. However, the large quantity of data that daylong recordings generate requires novel analytical tools to feasibly parse thousands of hours of naturalistic speech. This study outlines a new approach to efficiently process and sample from daylong audio recordings made in two bilingual communities, Spanish-English in the United States and Quechua-Spanish in Bolivia, to derive estimates of children's language exposure. Method We employed a general sampling with replacement technique to efficiently estimate two key elements of children's early language environments: (a) proportion of child-directed speech (CDS) and (b) dual language exposure. Proportions estimated from random sampling of 30-s segments were compared to those from annotations over the entire daylong recording (every other segment), as well as parental report of dual language exposure. Results Results showed that approximately 49 min from each recording or just 7% of the overall recording was required to reach a stable proportion of CDS and bilingual exposure. In both speech communities, strong correlations were found between bilingual language estimates made using random sampling and all-day annotation techniques. A strong association was additionally found for CDS estimates in the United States, but this was weaker at the Bolivian site, where CDS was less frequent. Dual language estimates from the audio recordings did not correspond well to estimates derived from parental report collected months apart. Conclusions Daylong recordings offer tremendous insight into children's daily language experiences, but they will not become widely used in developmental research until data processing and annotation time substantially decrease. We show that annotation based on random sampling is a promising approach to efficiently estimate ambient characteristics from daylong recordings that cannot currently be estimated via automated methods.

Analysis of acoustic and voice quality features for the classification of infant and mother vocalizations

Classification of infant and parent vocalizations, particularly emotional vocalizations, is critical to understanding how infants learn to regulate emotions in social dyadic processes. This work is an experimental study of classifiers, features, and data augmentation strategies applied to the task of classifying infant and parent vocalization types. Our data were recorded both in the home and in the laboratory. Infant vocalizations were manually labeled as cry, fus (fuss), lau (laugh), bab (babble) or scr (screech), while parent (mostly mother) vocalizations were labeled as ids (infant-directed speech), ads (adult-directed speech), pla (playful), rhy (rhythmic speech or singing), lau (laugh) or whi (whisper). Linear discriminant analysis (LDA) was selected as a baseline classifier, because it gave the highest accuracy in a previously published study covering part of this corpus. LDA was compared to two neural network architectures: a two-layer fully-connected network (FCN), and a convolutional neural network with self-attention (CNSA). Baseline features extracted using the OpenSMILE toolkit were augmented by extra voice quality, phonetic, and prosodic features, each targeting perceptual features of one or more of the vocalization types. Three web data augmentation and transfer learning methods were tested: pre-training of network weights for a related task (adult emotion classification), augmentation of under-represented classes using data uniformly sampled from other corpora, and augmentation of under-represented classes using data selected by a minimum cross-corpus information difference criterion. Feature selection using Fisher scores and experiments of using weighted and unweighted samplers were also tested. Two datasets were evaluated: a benchmark dataset (CRIED) and our own corpus. In terms of unweighted-average recall of CRIED dataset, the CNSA achieved the best UAR compared with previous studies. In terms of classification accuracy, weighted F1, and macro F1 of our own dataset, the neural networks both significantly outperformed LDA; the FCN slightly (but not significantly) outperformed the CNSA. Cross-examining features selected by different feature selection algorithms permits a type of post-hoc feature analysis, in which the most important acoustic features for each binary type discrimination are listed. Examples of each vocalization type of overlapped features were selected, and their spectrograms are presented, and discussed with respect to the type-discriminative acoustic features selected by various algorithms. MFCC, log Mel Frequency Band Energy, LSP frequency, and F1 are found to be the most important spectral envelope features; F0 is found to be the most important prosodic feature.

Vocal development in a large-scale crosslinguistic corpus

This study evaluates whether early vocalizations develop in similar ways in children across diverse cultural contexts. We analyze data from daylong audio recordings of 49 children (1-36 months) from five different language/cultural backgrounds. Citizen scientists annotated these recordings to determine if child vocalizations contained canonical transitions or not (e.g., "ba" vs. "ee"). Results revealed that the proportion of clips reported to contain canonical transitions increased with age. Furthermore, this proportion exceeded 0.15 by around 7 months, replicating and extending previous findings on canonical vocalization development but using data from the natural environments of a culturally and linguistically diverse sample. This work explores how crowdsourcing can be used to annotate corpora, helping establish developmental milestones relevant to multiple languages and cultures. Lower inter-annotator reliability on the crowdsourcing platform, relative to more traditional in-lab expert annotators, means that a larger number of unique annotators and/or annotations are required, and that crowdsourcing may not be a suitable method for more fine-grained annotation decisions. Audio clips used for this project are compiled into a large-scale infant vocalization corpus that is available for other researchers to use in future work.

How Chatty Are Daddies? An Exploratory Study of Infants' Language Environments

Purpose Fathers play a critical but underresearched role in their children's cognitive and linguistic development. Focusing on two-parent families with a mother and a father, the present longitudinal study explores the amount of paternal input infants hear during the first 2 years of life, how this input changes over time, and how it relates to child volubility. We devote special attention to parentese, a near-universal style of infant-directed speech, distinguished by its higher pitch, slower tempo, and exaggerated intonation. Method We examined the daylong recordings of the same 23 infants at ages 6, 10, 14, 18, and 24 months, given English-speaking families. The infants were recorded in the presence of their parents (mother-father dyads), who were predominantly White and ranged from mid to high socioeconomic status (SES). We analyzed the effects of parent gender and child age on adult word counts and parentese, as well as the effects of maternal and paternal word counts and parentese on child vocalizations. Results On average, the infants were exposed to 46.8% fewer words and 51.9% less parentese from fathers than from mothers, even though paternal parentese grew at a 2.8-times faster rate as the infants aged. An asymmetry emerged where maternal word counts and paternal parentese predicted child vocalizations, but paternal word counts and maternal parentese did not. Conclusions While infants may hear less input from their fathers than their mothers in predominantly White, mid-to-high SES, English-speaking households, paternal parentese still plays a unique role in their linguistic development. Future research on sources of variability in child language outcomes should thus control for parental differences since parents' language can differ substantially and differentially predict child language.

Symbolic play provides a fertile context for language development

In this study, we test the hypothesis that symbolic play represents a fertile context for language acquisition because its inherent ambiguity elicits communicative behaviors that positively influence development. Infant-caregiver dyads (N = 54) participated in two 20-minute play sessions six months apart (Time 1 = 18 months, Time 2 = 24 months). During each session, the dyads played with two sets of toys that elicited either symbolic or functional play. The sessions were transcribed and coded for several features of dyadic interaction and language; infants' linguistic proficiency was measured via parental report. The two contexts elicited different communicative and linguistic behaviors. Notably, the symbolic play condition resulted in significantly greater conversational turn-taking than functional play, and also resulted in the greater use of questions and mimetics in infant-directed speech (IDS). In contrast, caregivers used more imperative clauses in functional play. Correlational and regression analyses showed that frequent properties of symbolic play (i.e., turn-taking, yes-no questions, mimetics) were positively related to infants' language proficiency, whereas frequent features of functional play (i.e., imperatives in IDS) were negatively related. The results provide evidence supporting the hypothesis that symbolic play is a fertile context for language development, driven by the need to negotiate meaning.

Practice and experience predict coarticulation in child speech

Much research in child speech development suggests that young children coarticulate more than adults. There are multiple, not mutually-exclusive, explanations for this pattern. For example, children may coarticulate more because they are limited by immature motor control. Or they may coarticulate more if they initially represent phonological segments in larger, more holistic units such as syllables or feet. We tested the importance of several different explanations for coarticulation in child speech by evaluating how four-year-olds' language experience, speech practice, and speech planning predicted their coarticulation between adjacent segments in real words and paired nonwords. Children with larger vocabularies coarticulated less, especially in real words, though there were no reliable coarticulatory differences between real words and nonwords after controlling for word duration. Children who vocalized more throughout a daylong audio recording also coarticulated less. Quantity of child vocalizations was more predictive of the degree of children's coarticulation than a measure of receptive language experience, adult word count. Overall, these results suggest strong roles for children's phonological representations and speech practice, as well as their immature fine motor control, for coarticulatory development.

Vocal imitation between mothers and infants

The aim of the present mixed cross-sectional and longitudinal study was to observe and describe some aspects of vocal imitation in natural mother-infant interaction. Specifically, maternal imitation of infant utterances was observed in relation to the imitative modeling, mirrored equivalence, and social guided learning models of infant speech development. Nine mother-infant dyads were audio-video recorded. Infants were recruited at different ages between 6 and 11 months and followed for 3 months, providing a quasi-longitudinal series of data from 6 through 14 months of age. It was observed that maternal imitation was more frequent than infant imitation even though vocal imitation was a rare maternal response. Importantly, mothers used a range of contingent and noncontingent vocal responses in interaction with their infants. Mothers responded to three-quarters of their infant's vocalizations, including speech-like and less mature vocalization types. The infants' phonetic repertoire expanded with age. Overall, the findings are most consistent with the social guided learning approach. Infants rarely imitated their mothers, suggests a creative self-motivated learning mechanism that requires further investigation.

Adult responses to infant prelinguistic vocalizations are associated with infant vocabulary: A home observation study

This study used LENA recording devices to capture infants' home language environments and examine how qualitative differences in adult responding to infant vocalizations related to infant vocabulary. Infant-directed speech and infant vocalizations were coded in samples taken from daylong home audio recordings of 13-month-old infants. Infant speech-related vocalizations were identified and coded as either canonical or non-canonical. Infant-directed adult speech was identified and classified into different pragmatic types. Multiple regressions examined the relation between adult responsiveness, imitating, recasting, and expanding and infant canonical and non-canonical vocalizations with caregiver-reported infant receptive and productive vocabulary. An interaction between adult like-sound responding (i.e., the total number of imitations, recasts, and expansions) and infant canonical vocalizations indicated that infants who produced more canonical vocalizations and received more adult like-sound responses had higher productive vocabularies. When sequences were analyzed, infant canonical vocalizations that preceded and followed adult recasts and expansions were positively associated with infant productive vocabulary. These findings provide insights into how infant-adult vocal exchanges are related to early vocabulary development.

Exploratory dynamics of vocal foraging during infant-caregiver communication

We investigated the hypothesis that infants search in an acoustic space for vocalisations that elicit adult utterances and vice versa, inspired by research on animal and human foraging. Infant-worn recorders were used to collect day-long audio recordings, and infant speech-related and adult vocalisation onsets and offsets were automatically identified. We examined vocalisation-to-vocalisation steps, focusing on inter-vocalisation time intervals and distances in an acoustic space defined by mean pitch and mean amplitude, measured from the child's perspective. Infant inter-vocalisation intervals were shorter immediately following a vocal response from an adult. Adult intervals were shorter following an infant response and adult inter-vocalisation pitch differences were smaller following the receipt of a vocal response from the infant. These findings are consistent with the hypothesis that infants and caregivers are foraging vocally for social input. Increasing infant age was associated with changes in inter-vocalisation step sizes for both infants and adults, and we found associations between response likelihood and acoustic characteristics. Future work is needed to determine the impact of different labelling methods and of automatic labelling errors on the results. The study represents a novel application of foraging theory, demonstrating how infant behaviour and infant-caregiver interaction can be characterised as foraging processes.

A meta-analysis of the predictability of LENA™ automated measures for child language development

Early language environment plays a critical role in child language development. The Language ENvironment Analysis (LENA™) system allows researchers and clinicians to collect daylong recordings and obtain automated measures to characterize a child's language environment. This meta-analysis evaluates the predictability of LENA's automated measures for language skills in young children. We systematically searched reports for associations between LENA's automated measures, specifically, adult word count (AWC), conversational turn count (CTC), and child vocalization count (CVC), and language skills in children younger than 48 months. Using robust variance estimation, we calculated weighted mean effect sizes and conducted moderator analyses exploring the factors that might affect this relationship. The results revealed an overall medium effect size for the correlation between LENA's automated measures and language skills. This relationship was largely consistent regardless of child developmental status, publication status, language assessment modality and method, or the age at which the LENA recording was taken; however, the effect was weakly moderated by the gap between LENA recordings and language measures taken. Among the three measures, there were medium associations between CTC and CVC and language, whereas there was a small-to-medium association between AWC and language. These findings extend beyond validation work conducted by the LENA Research Foundation and suggest certain predictive strength of LENA's automated measures for child language. We discussed possible mechanisms underlying the observed associations, as well as the theoretical, methodological, and clinical implications of these findings.