Canonical babbling trajectories across the first year of life in autism and typical development.

LAY ABSTRACT: Our study examined how babies develop their ability to talk to help identify early signs of autism. We looked at babies' production of babbling with mature syllables across the first year of life. Babies usually start producing mature babbling at 7 months of age before they say their first words. Some studies have suggested that babies who are later diagnosed with autism produce this kind of babbling less frequently in their first year of life, but other studies have shown complicated outcomes. In this new study, we followed 44 autistic babies and compared them to 127 typically developing babies. We recorded the babies once every month, all day long, from the time that they were born until they were around 13 months old. Then, we studied their mature babbling from segments of these recordings. We found that the rate at which babies used mature babbling was lower in boys with autism, and higher in girls with autism, compared to babies without autism. This research helps us understand how babies with autism learn to talk. It also raises important questions about differences between boys and girls with autism. Our study can help us improve how scientists and clinicians can identify autism earlier, which could lead to better communication supports for autistic children and their families.

Developmental cascades of vocal turn-taking connect prelinguistic vocalizing with early language.

Conversational turn-taking is ubiquitously found in caregiver-infant interactions, and robustly predictive of infant communicative development. Over the first year, infants take quick adult-like vocal turns with caregivers. Many studies have documented the consistency of caregiver responsiveness and its influence on infant rapid language growth. However, few have examined how caregiver responsiveness facilitates extended vocal turn-taking in real-time with infants over the first year. The influence of prelinguistic vocal turn-taking on the emergence of language has also been under-investigated. We analyzed free-play sessions of 30 caregivers and their infants at both 5 and 10 months, and obtained infant language outcomes at 18 months. We examined the developmental consistency (group-level continuity and dyad-order stability) and change of infant volubility, caregiver responses to babbling in vocal, non-vocal and multimodal modalities, and the influence of modality on caregiver-infant vocal turn-taking. Caregiver contingent responsiveness to infant babbling at 5 months predicted vocal turn-taking at 10 months. Developmental increases in prelinguistic vocalizing and vocal turn-taking from 5 to 10 months predicted infant language outcomes at 18 months. At both 5 and 10 months, caregiver vocal responses were more effective in extending turn-taking than non-vocal or multimodal responses. In summary, prelinguistic vocal turn-taking, facilitated by caregiver vocal responsiveness, is positively related to the emergence of early language.

Babbling opens the sensory phase for imitative vocal learning.

Zebra finches, a species of songbirds, learn to sing by creating an auditory template through the memorization of model songs (sensory learning phase) and subsequently translating these perceptual memories into motor skills (sensorimotor learning phase). It has been traditionally believed that babbling in juvenile birds initiates the sensorimotor phase while the sensory phase of song learning precedes the onset of babbling. However, our findings challenge this notion by demonstrating that testosterone-induced premature babbling actually triggers the onset of the sensory learning phase instead. We reveal that juvenile birds must engage in babbling and self-listening to acquire the tutor song as the template. Notably, the sensory learning of the template in songbirds requires motor vocal activity, reflecting the observation that prelinguistic babbling in humans plays a crucial role in auditory learning for language acquisition.

Early corticosterone increases vocal complexity in a wild parrot: An organizational role of the hypothalamic-pituitary-adrenal axis in vocal learning?

The neuroendocrinology of vocal learning is exceptionally well known in passerine songbirds. Despite huge life history, genetic and ecological variation across passerines, song learning tends to occur as a result of rises in gonadal and non-gonadal sex steroids that shape telencephalic vocal control circuits and song. Parrots are closely related but independently evolved different cerebral circuits for vocal repertoire acquisition in both sexes that serve a broader suite of social functions and do not appear to be shaped by early androgens or estrogens; instead, parrots begin a plastic phase in vocal development at an earlier life history stage that favors the growth, maturation, and survival functions of corticosteroids. As evidence, corticosterone (CORT) supplements given to wild green-rumped parrotlets (Forpus passerinus) during the first week of vocal babbling resulted in larger vocal repertoires in both sexes in the remaining days before fledging. Here, we replicate this experiment but began treatment 1 week before in development, analyzing both experiments in one model and a stronger test of the organizational effects of CORT on repertoire acquisition. Early CORT treatment resulted in significantly larger repertoires compared to late treatment. Both treatment groups showed weak negative effects on the early, reduplicated stage of babbling and strong, positive effects of CORT on the later, variegated stage. Results are consistent with more formative effects of corticosteroids at earlier developmental stages and a role of the hypothalamic-pituitary-adrenal axis (HPA) in vocal repertoire acquisition. Given the early emergence of speech in human ontogeny, parrots are a promising model for understanding the putative role of the HPA axis in the construction of neural circuits that support language acquisition.

Babbling in extremely premature infants at 12 months corrected age.

Babbling is an important precursor to speech in infancy, and deviations from the typical babbling development can predict later difficulties in speech, language, and communication. This cross-sectional study aimed to investigate babbling and early speech in Swedish extremely premature infants. Samples of babbling were collected from 20 extremely premature infants (EPT group) at the corrected age of 12 months. Data collection was home-based and consisted of an audio-video recording of each infant playing with a parent. Presence of canonical babbling (CB), and three oral stop variables distinctive of typical babbling, and consonant inventory were assessed. The assessment was performed during a standardised observation of babbling. Data from the EPT group were compared to previously collected data of a reference group of 20 10-month-old infants without known medical diagnoses. The results showed that the EPT group had a lower proportion of infants producing CB, and that they used a significantly smaller consonant inventory compared to the reference group. Although not statistically significant, oral stops were less frequently found in the EPT group. The findings of a restricted consonant inventory and low proportion of CB in the EPT group are not surprising considering that the group has been found to be at risk of speech and language delay in toddlerhood. Still, further research is needed to explore whether babbling at 12 months can predict speech and language skills at an older age in extremely premature infants.

Melody of Vocants: Fixed Pattern or Shaped by Hearing?

INTRODUCTION: Vocants as infants' first vocalic utterances are produced laryngeally while the vocal tract is maintained in a neutral position. These "primitive" sounds have sometimes been described as largely innate and, therefore, as sounding alike in both healthy and hearing-impaired young infants. OBJECTIVE: The objective of this study is to compare melody features of vocants, recorded during face-to-face interaction, between infants (N = 8) with profound congenital sensorineural hearing loss (HI group) and age-matched (N = 18) controls (CO) group. The question was as follows: does a lack of auditory feedback have a noticeable effect on melodic features of vocants? METHODS: The cooing database totalled 6,998 vocalizations (HI: N = 2,847; CO: N = 4,151), all of which had been recorded during the observation period of 60-181 days of age. Identification of the vocants (N = 1,148) was based on broadband spectrograms (KAY-CSL) and auditory impressions. Fundamental frequency (F0) analyses were performed (PRAAT) and the pattern of the F0 contour (melody) analysed using specific in-lab software (CDAP, pw-project). Generalized mixed linear models were used to perform group comparisons. RESULTS: There was a clear predominance of a simple rising-falling pattern (single melody arcs) in vocants of both groups. Nonetheless, significantly more complex contours, particularly, double-arc structures, were found in vocants of the CO group. Moreover, vocants of the HI group were shorter than those uttered by the CO group, while the mean F0 did not significantly differ. CONCLUSION: Vocants are characterized by both, innate features, found in HI and CO groups, and features that additionally require a functioning auditory system. Even at an early pre-linguistic stage, somatosensory sensations cannot compensate for a lack of auditory feedback. Vocants might be relevant in the early diagnosis of hearing disorders and assessments of the effectiveness of, or adjustments required to, hearing aids.

Profiling the Longitudinal Development of Babbling in Infants with Cerebral Palsy: Validation of the Infant Monitor of Vocal Production (IMP) Using the Stark Assessment of Early Vocal Development-Revised (SAEVD-R).

AIM: We compared early vocal development in children "at risk" for cerebral palsy (CP) with typically developing (TD) infants aged 6 to 15 months using the SAEVD-R, investigating potential pre-linguistic markers of communication impairment. Additionally, we sought to examine the agreement between the SAEVD-R and IMP, which uses parent report, in identifying departure from typical vocal development in at-risk infants. METHOD: Utilising a longitudinal cohort study, >10,000 vocalisations of 33 infants (15 at risk for CP and 18 TD) were assessed at 6, 9, 12, and 15 months using the SAEVD-R. Generalised linear mixed models (GLMMs) compared groups, and Spearman correlations explored IMP ceiling scores and SAEVD-R measures. RESULTS: At 6 months, both TD and CP groups reached SAEVD-R vocalisation level 3 (expansion). By 9 months, 51% of TD infants progressed to advanced babbling (levels 4 and 5), while 80% of at-risk infants remained at level 3. At 12 and 15 months, over 90% of TD children advanced, compared to 67% at 12 months and 53% at 15 months for at-risk infants, who stayed at the pre-canonical stage. Strong correlations were found between IMP scores and vocalisation levels at 9 and 12 months. Remaining at the pre-canonical stage at 12 months correlated with delayed vocal development as per IMP scores. INTERPRETATION: TD infants achieved higher SAEVD-R levels than at-risk infants. At 12 months, IMP scores effectively identified infants with speech-like vocalisation difficulties, demonstrating its clinical utility in identifying atypical vocal development in infants at risk for CP.

Fundamental Frequency Contour (Melody) of Infant Vocalizations across the First Year.

INTRODUCTION: The fundamental frequency contour (melody) of cry and non-cry utterances becomes more complex with age. However, there is a lack of longitudinal analyses of melody development during the first year of life. OBJECTIVE: The aim of the study was to longitudinally analyze melody development in typical vocalization types across the first 12 months of life. The aim was twofold: (1) to answer the question whether melody becomes more complex in all vocalization types with age and (2) to characterize complex patterns in more detail. METHODS: Repeatedly recorded vocalizations (n = 10,988) of 10 healthy infants (6 female) over their first year of life were analyzed using frequency spectrograms and fundamental frequency (f0) analyses (PRAAT). Melody complexity analysis was performed using specific in-lab software (CDAP, pw-project) in a final subset of 9,237 utterances that contained noise-free, undisturbed contours. Generalized mixed linear models were used to analyze age and vocalization type effects on melody complexity. RESULTS: The vocalization repertoire showed a higher proportion of complex melodies from the second month onward. The age effect was significant, but no difference was found in melody complexity between cry and non-cry vocalizations across the first 6 months. From month 7-12, there was a further significant increase in complex structures only in canonical babbling not in marginal babbling. Melody segmentations by laryngeal constrictions prevailed among complex shapes. CONCLUSION: The study demonstrated the regularity of melody development in different vocalization types throughout the first year of life. In terms of prosodic features of infant sounds, melody contour is of primary importance, and further studies are required that also include infants at risk for language development.

The validity of LENA technology for assessing the linguistic environment and interactions of infants learning Hebrew and Arabic.

The present study assessed LENA's suitability as a tool for monitoring future language interventions by evaluating its reliability, construct validity, and criterion validity in infants learning Hebrew and Arabic, across low and high levels of maternal education. Participants were 32 infants aged 3 to 11 months (16 in each language) and their mothers, whose socioeconomic status (SES) was determined based on their years of education (H-high or L-low ME-maternal education). The results showed (1) good reliability for the LENA's automatic count on adult word count (AWC), conversational turns (CTC), and infant vocalizations (CVC), based on the positive associations and fair to excellent agreement between the manual and automatic counts; (2) good construct validity based on significantly higher counts for HME vs. LME and positive associations between LENA's automatic vocal assessment (AVA) and developmental questionnaire (DA) and age; and (3) good concurrent criterion validity based on the positive associations between the LENA counts for CTC, CVC, AVA, and DA and the scores on the preverbal parent questionnaire (PRISE). The present study supports the use of LENA in early intervention programs for infants whose families speak Hebrew or Arabic. The LENA could be used to monitor the efficacy of these programs as well as to provide feedback to parents on the amount of language experience their infants are getting and their progress in vocal production. The results also indicate a potential utility of LENA in assessing linguistic environments and interactions in Hebrew- and Arabic-speaking infants with developmental disorders, such as hearing impairment and cerebral palsy.

Inter-rater reliability in classification of canonical babbling status based on canonical babbling ratio in infants with isolated cleft palate randomised to Timing of Primary Surgery for Cleft Palate (TOPS).

Canonical babbling (CB) is commonly defined as present when at least 15% of all syllables produced are canonical, in other words a canonical babbling ratio (CBR) ≥0.15. However, there is limited knowledge about inter-rater reliability in classification of CB status based on CBR and inter-rater differences in assessment of CBR. We investigated inter-rater reliability of experienced Speech Language Therapists (SLTs) on: classification of CB status based on CBR ≥ 0.15, CBRs and the total number of syllables per infant used to calculate CBR.Each infant (n = 484) was video-recorded at a clinical site in play interaction with their parent as part of the randomised controlled trial Timing of Primary Surgery for Cleft Palate. Each recording was subsequently assessed by three independent SLTs, from a pool of 29 SLTs. They assessed the recordings in real time.The three assessing SLTs agreed in classification of CB status in 423 (87.4%) infants, with higher complete agreement for canonical (91%; 326/358) than non-canonical (77%; 97/126). The average difference in CBR and total number of syllables identified between the SLT assessments of each infant was 0.12 and 95, respectively.This study provided new evidence that one trained SLT can reliably classify CB status (CBR ≥ 0.15) in real time when there is clear distinction between the observed CBR and the boundary (0.15); however, when the observed CBR approaches the boundary multiple SLT assessments are beneficial. Thus, we recommend to include assessment of inter-rater reliability, if the purpose is to compare CBR and total syllable count across infants or studies.Trial registration number here: www.clinicaltrials.gov, identifier NCT00993551.

A Probe Study on Vocal Development in Two Infants at Risk for Cerebral Palsy.

The present work examined canonical babbling ratios longitudinally as a measure of onset and consolidation of canonical babbling in two infants at risk of cerebral palsy (CP) between 5 and 16 months. Ten typically developing infants were included for comparison at 6, 9, 12, and 16-19 months. Canonical babbling ratios (CBRs) were calculated from 5-min segments, and follow-up diagnostic outcomes were collected between 24 and 33 months. The two infants at risk demonstrated low CBR growth trajectories compared to the typical infant group, and slightly different patterns of consolidation. The two infants at risk were later diagnosed with different levels of CP and speech impairment severity. All infants demonstrated greater variability than expected. Studying canonical babbling and other prelinguistic milestones in this population may inform our perspective of the involvement of the motor system in the vocal domain. Additional implications on the analysis of canonical babbling using all-day home recordings are discussed.

Vocalisation Repertoire at the End of the First Year of Life: An Exploratory Comparison of Rett Syndrome and Typical Development.

Rett syndrome (RTT) is a rare, late detected developmental disorder associated with severe deficits in the speech-language domain. Despite a few reports about atypicalities in the speech-language development of infants and toddlers with RTT, a detailed analysis of the pre-linguistic vocalisation repertoire of infants with RTT is yet missing. Based on home video recordings, we analysed the vocalisations between 9 and 11 months of age of three female infants with typical RTT and compared them to three age-matched typically developing (TD) female controls. The video material of the infants had a total duration of 424 min with 1655 infant vocalisations. For each month, we (1) calculated the infants' canonical babbling ratios with CBRUTTER, i.e., the ratio of number of utterances containing canonical syllables to total number of utterances, and (2) classified their pre-linguistic vocalisations in three non-canonical and four canonical vocalisation subtypes. All infants achieved the milestone of canonical babbling at 9 months of age according to their canonical babbling ratios, i.e. CBRUTTER ≥ 0.15. We revealed overall lower CBRsUTTER and a lower proportion of canonical pre-linguistic vocalisations consisting of well-formed sounds that could serve as parts of target-language words for the RTT group compared to the TD group. Further studies with more data from individuals with RTT are needed to study the atypicalities in the pre-linguistic vocalisation repertoire which may portend the later deficits in spoken language that are characteristic features of RTT.

Asking parents about babbling at 10 months produced valid answers but did not predict language screening result 2 years later.

AIM: We evaluated the concurrent and predictive validity of questions to parents of 10-month-old children about babbling. METHODS: Children with at least one native Swedish-speaking parent were eligible for inclusion in this prospective longitudinal study. The parents were asked three questions about babbling at a routine healthcare visit. If parents reported a lack of canonical babbling (CB), children were assessed by a speech and language pathologist to evaluate the questions' concurrent validity. We then examined whether the babbling questions predicted which children would fail the routine language screening at 2.5/3 years. RESULTS: Fifteen of the 1126 children lacked CB according to the parent responses and the expert assessment confirmed 12 of these cases, providing a concurrent validity of 80%. The sensitivity to predict routine language screening was 8% (95% confidence interval 3-17), and the positive predictive value was 40% (95% confidence interval 20%-65%). However, only six of the children lacking CB at 10 months were among the 71 children who failed later language screening. CONCLUSION: This study suggests that the babbling questions could be included in the 10-month surveillance at the child health services as valid measures of babbling development, but they cannot predict language screening result at 2.5/3 years.

A convergent interaction engine: vocal communication among marmoset monkeys.

To understand the primate origins of the human interaction engine, it is worthwhile to focus not only on great apes but also on callitrichid monkeys (marmosets and tamarins). Like humans, but unlike great apes, callitrichids are cooperative breeders, and thus habitually engage in coordinated joint actions, for instance when an infant is handed over from one group member to another. We first explore the hypothesis that these habitual cooperative interactions, the marmoset interactional ethology, are supported by the same key elements as found in the human interaction engine: mutual gaze (during joint action), turn-taking, volubility, as well as group-wide prosociality and trust. Marmosets show clear evidence of these features. We next examine the prediction that, if such an interaction engine can indeed give rise to more flexible communication, callitrichids may also possess elaborate communicative skills. A review of marmoset vocal communication confirms unusual abilities in these small primates: high volubility and large vocal repertoires, vocal learning and babbling in immatures, and voluntary usage and control. We end by discussing how the adoption of cooperative breeding during human evolution may have catalysed language evolution by adding these convergent consequences to the great ape-like cognitive system of our hominin ancestors. This article is part of the theme issue 'Revisiting the human 'interaction engine': comparative approaches to social action coordination'.

Vocal babbling in a wild parrot shows life history and endocrine affinities with human infants.

Prelinguistic babbling is a critical phase in infant language development and is best understood in temperate songbirds where it occurs primarily in males at reproductive maturity and is modulated by sex steroids. Parrots of both sexes are icons of tropical vocal plasticity, but vocal babbling is unreported in this group and whether the endocrine system is involved is unknown. Here we show that vocal babbling is widespread in a wild parrot population in Venezuela, ensues in both sexes during the nestling stage, occurs amidst a captive audience of mixed-aged siblings, and is modulated by corticosteroids. Spectrographic analysis and machine learning found phoneme diversity and combinatorial capacity increased precipitously for the first week, thereafter, crystalizing into a smaller repertoire, consistent with the selective attrition model of language development. Corticosterone-treated nestlings differed from unmanipulated birds and sham controls in several acoustic properties and crystallized a larger repertoire post-treatment. Our findings indicate babbling occurs during an early life-history stage in which corticosteroids help catalyse the transition from a universal learning programme to one finely tuned for the prevailing ecological environment, a potentially convergent scenario in human prelinguistic development.

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.

Early Vocal Development in Tuberous Sclerosis Complex.

BACKGROUND: Our goal was to assess for the first time early vocalizations as precursors to speech in audio-video recordings of infants with tuberous sclerosis complex (TSC). METHODS: We randomly selected 40 infants with TSC from the TSC Autism Center of Excellence Research Network dataset. Using human observers, we analyzed 74 audio-video recordings within a flexible software-based coding environment. During the recordings, infants were engaged in developmental testing. We determined syllables per minute (volubility), the number of consonant-vowel combinations, such as 'ba' (canonical babbling), and the canonical babbling ratio (canonical syllables/total syllables) and compared the data with two groups of typically developing (TD) infants. One comparison group's data had come from a laboratory setting, while the other's had come from all-day Language Environment Analysis recordings at home. RESULTS: Compared with TD infants in laboratory and all-day Language Environment Analysis recordings, entry into the canonical babbling stage was delayed in the majority of infants with TSC, and the canonical babbling ratio was low (TD mean = 0.346, SE = 0.19; TSC mean = 0.117, SE = 0.023). Volubility level in infants with TSC was less than half that of TD infants (TD mean = 9.82, SE = 5.78; TSC mean = 3.99, SE = 2.16). CONCLUSIONS: Entry into the canonical stage and other precursors of speech development were delayed in infants with TSC and may signal poor language and developmental outcomes. Future studies are planned to assess prediction of language and developmental outcomes using these measures in a larger sample and in more precisely comparable recording circumstances.

Cross-species parallels in babbling: animals and algorithms.

A key feature of vocal ontogeny in a variety of taxa with extensive vocal repertoires is a developmental pattern in which vocal exploration is followed by a period of category formation that results in a mature species-specific repertoire. Vocal development preceding the adult repertoire is often called 'babbling', a term used to describe aspects of vocal development in species of vocal-learning birds, some marine mammals, some New World monkeys, some bats and humans. The paper summarizes the results of research on babbling in examples from five taxa and proposes a unifying definition facilitating their comparison. There are notable similarities across these species in the developmental pattern of vocalizations, suggesting that vocal production learning might require babbling. However, the current state of the literature is insufficient to confirm this suggestion. We suggest directions for future research to elucidate this issue, emphasizing the importance of (i) expanding the descriptive data and seeking species with complex mature repertoires where babbling may not occur or may occur only to a minimal extent; (ii) (quasi-)experimental research to tease apart possible mechanisms of acquisition and/or self-organizing development; and (iii) computational modelling as a methodology to test hypotheses about the origins and functions of babbling. This article is part of the theme issue 'Vocal learning in animals and humans'.

Protophones, the precursors to speech, dominate the human infant vocal landscape.

Human infant vocalization is viewed as a critical foundation for vocal learning and language. All apes share distress sounds (shrieks and cries) and laughter. Another vocal type, speech-like sounds, common in human infants, is rare but not absent in other apes. These three vocal types form a basis for especially informative cross-species comparisons. To make such comparisons possible we need empirical research documenting the frequency of occurrence of all three. The present work provides a comprehensive portrayal of these three vocal types in the human infant from longitudinal research in various circumstances of recording. Recently, the predominant vocalizations of the human infant have been shown to be speech-like sounds, or 'protophones', including both canonical and non-canonical babbling. The research shows that protophones outnumber cries by a factor of at least five based on data from random-sampling of all-day recordings across the first year. The present work expands on the prior reports, showing the protophones vastly outnumber both cry and laughter in both all-day and laboratory recordings in various circumstances. The data provide new evidence of the predominance of protophones in the infant vocal landscape and illuminate their role in human vocal learning and the origin of language. This article is part of the theme issue 'Vocal learning in animals and humans'.