Speech-like vocalizations in infancy: an evaluation of potential risk factors

Features of animal babbling in the vocal ontogeny of the gray mouse lemur (Microcebus murinus)

In human infants babbling is an important developmental stage of vocal plasticity to acquire maternal language. To investigate parallels in the vocal development of human infants and non-human mammals, seven key features of human babbling were defined, which are up to date only shown in bats and marmosets. This study will explore whether these features can also be found in gray mouse lemurs by investigating how infant vocal streams gradually resemble the structure of the adult trill call, which is not present at birth. Using unsupervised clustering, we distinguished six syllable types, whose sequential order gradually reflected the adult trill. A subset of adult syllable types was produced by several infants, with the syllable production being rhythmic, repetitive, and independent of the social context. The temporal structure of the calling bouts and the tempo-spectral features of syllable types became adult-like at the age of weaning. The age-dependent changes in the acoustic parameters differed between syllable types, suggesting that they cannot solely be explained by physical maturation of the vocal apparatus. Since gray mouse lemurs exhibit five features of animal babbling, they show parallels to the vocal development of human infants, bats, and marmosets.

Sex differences in infant vocalization and the origin of language

Seeking to discern the earliest sex differences in language-related activities, our focus is vocal activity in the first two years of life, following up on recent research that unexpectedly showed boys produced significantly more speech-like vocalizations (protophones) than girls during the first year of life.We now bring a much larger body of data to bear on the comparison of early sex differences in vocalization, data based on automated analysis of all-day recordings of infants in their homes. The new evidence, like that of the prior study, also suggests boys produce more protophones than girls in the first year and offers additional basis for informed speculation about biological reasons for these differences. More broadly, the work offers a basis for informed speculations about foundations of language that we propose to have evolved in our distant hominin ancestors, foundations also required in early vocal development of modern human infants.

Toddlers at Elevated Likelihood for Autism: Exploring Sensory and Language Treatment Predictors

Baseline child characteristics may predict treatment outcomes in children with or at elevated likelihood of developing autism (EL-ASD). Little is known about the role of child sensory and language features on treatment outcome. Participants were randomly assigned to a parent-mediated intervention or control condition. Analyses explored the relationship between baseline child sensory and language characteristics and changes in ASD symptoms over approximately 9 months. Higher baseline sensory hyporeactivity was significantly related to less improvement in social communication (SC) for the treatment group only. More baseline atypical vocalizations were significantly related to less improvement on SC across treatment and control groups. This work provides an initial framework to encourage the tailoring of interventions for EL-ASD children, suggesting sensory reactivity and atypical vocalizations may be useful behaviors to consider in treatment planning.

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.

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.

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.

Longitudinal Study of Vocal Development and Language Environments in Infants With Cleft Palate

OBJECTIVE

This study investigated vocalization and language environment longitudinally in infants with cleft palate (CP) based on day-long audio recordings collected in their natural environments.

DESIGN

Language Environment Analysis (LENA) data from all-day recordings at home were collected at 3-month intervals for infants from 4-6 to 16-18 months of age. The recordings were analyzed using experimentally blinded human coding as well as LENA automated analysis.

PARTICIPANTS

Ten infants with CP (± cleft lip) and 10 age-matched infants without CP.

MAIN OUTCOME MEASURES

Several measurements were obtained from the LENA automated analysis software. In addition, human coded measurements of vocalization and language environment, including the true canonical babbling ratio and the infant-directed speech ratio, were analyzed for each time point of data collection for each infant. Statistical analyses were performed to conduct group and age comparisons for each measure of vocalization and language environment.

RESULTS

No group differences emerged in number of syllables produced. Infants with CP exhibited late onset and fewer productions of canonical syllables compared to infants without CP. Infants with CP did not show significant differences from infants without CP in measures related to language environment across ages.

CONCLUSION

This study provides detailed information through naturalistic all-day home recordings about vocal development and early language environments in infants with CP before and after palatal repair. Clinical implications for early intervention are discussed.

Canonical babbling ratio - Concurrent and predictive evaluation of the 0.15 criterion

INTRODUCTION

Canonical babbling ratio (CBR) is a commonly used measure to quantify canonical babbling (CB), and 0.15 is the commonly accepted criterion for the canonical babbling stage. However, this has not been thoroughly investigated. The aim of this study was to evaluate the validity of this criterion using concurrent and predictive comparisons.

METHODS

Longitudinal data from 50 children recruited in different clinical projects were used. At 10 months of age, CBR was calculated based on counted utterances from audio-video recorded parent-child interactions. The videos were also assessed by CB observation, where an observer made an overall judgement on whether the child was in the canonical babbling stage or not. For the concurrent evaluation, CBR was compared to CB observation as a reference test, using area under the curve (AUC). The criterion resulting in the best combination of sensitivity and specificity was identified using positive likelihood ratios. In the predictive comparisons CBR was analyzed as a predictor of speech/language difficulties at 30-36 months. Participants presenting with difficulties in consonant production and/or parent-reported vocabulary were considered to have speech/language difficulties. Sensitivity and specificity were compared for CBR using the 0.15 criterion and the new criterion identified in this study.

RESULTS

An AUC of 0.87 indicated that CBR is a valid measure of canonical babbling in 10-month-old children. The best combination of sensitivity and specificity was found at a criterion of 0.14 (sensitivity 0.96, specificity 0.70). In the predictive comparison, CBR with a 0.14 or 0.15 criterion revealed the same sensitivity (0.71) but 0.14 showed a slightly better specificity (0.52 versus 0.42).

CONCLUSIONS

CBR is a valid measure of CB (at 10 months). However, when using CBR to classify children's babbling as canonical or non-canonical, researchers need to carefully consider the implications of the chosen criterion.

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.

Adding a fourth rater to three had little impact in pre-linguistic outcome classification

The consequence of differing levels of agreement across raters is rarely studied. Subsequently, knowledge is limited on how number of raters affects the outcome. The present study aimed to examine the impact on pre-linguistic outcome classifications of 12-month-old infants when using four raters compared to three. Thirty experienced Speech and Language Therapists (SLTs) from five countries assessed 20 minute video recordings of four 12-month-old infants during a play session with a parent. One recording was assessed twice. A naturalistic listening method in real time was used. This involved: (1) assessing, each syllable as canonical or non-canonical, and (2) following the recording, assessing if the infant was babbling canonically and listing the syllables the infant produced with command. The impact that four raters had on outcome, compared to three, was explored by classifying the outcome based on all possible combinations of three raters and determining the frequency that the outcome assessment changed when a fourth assessor was added. Results revealed that adding a fourth rater had a minimal impact on canonical babbling ratio assessment. Presence/absence of canonical babbling and size of consonant inventory showed a negligible impact on three out of four recordings, whereas the size of syllable inventory and presence/absence of canonical babbling was minimally affected in one recording by adding a fourth rater. In conclusion, adding a forth rater in assessment of pre-linguistic utterances in 12-month-old infants with naturalistic assessment in real time does not affect outcome classifications considerably. Thus, using three raters, as opposed to four, is recommended.

Prelexical phonetic and early lexical development in German-acquiring infants: canonical babbling and first spoken words

Prelexical phonetic capacities have widely been described to be a precursor for later speech and language development. However, studies so far varied greatly in the measurements used for the detection of canonical babbling onset or the description of infants' phonetic capacities at one or more set time points. The comparability of results is, therefore, questionable. Thus, the aims of this study were to investigate the associations between (1) different measurements of CBO, (2) different aspects of phonetic capacity at the age of 9 months and (3) age of CBO and phonetic capacities at 9 months. A further aim (4) was to explore whether one of the measures would be suitable to predict the age of word onset (WO) in 20 healthy German-acquiring individuals. The data were derived from monthly recorded spontaneous speech samples between 0 and 18 months. It was found that the different applied prelexical measures equally well serve as valid estimators for the detection of CBO or of infants' phonetic capacities. Further, age of CBO and phonetic capacities at 9 months were significantly associated even though the age of CBO did not reliably predict phonetic capacities. Prelexical measures and WO were not related. Reasons for no indication of a significant association are discussed.

Canonical Babbling and Early Consonant Development Related to Hearing in Children With Otitis Media With Effusion With or Without Cleft Palate

OBJECTIVE

To investigate and compare babbling, early consonant production and proficiency from 10 to 36 months of age and its relationship with hearing in children with otitis media with effusion (OME) with or without cleft palate.

DESIGN

Prospective, longitudinal group comparison study.

SETTING

University hospital.

PARTICIPANTS

Fifteen children born with nonsyndromic cleft palate with or without cleft lip (CP±L) and 15 age-matched children with hearing loss (HL) associated with OME but without cleft palate (noncleft group).

MAIN OUTCOME MEASURES

Canonical babbling (CB) and early consonant variables (presence of oral stops, anterior stops, dental/alveolar stops, number of different true consonants) at 10 and 18 months, and percentage of consonants correct proficiency (PCC) at 36 months.

RESULTS

A total of 54% of the CP±L group and 77% of the noncleft group had CB. The noncleft group had a significantly higher prevalence of all consonant variables. Percentage of consonants correct was 61.9% in the CP±L group and 81.6% in the noncleft group. All early consonant variables except CB were significantly related to PCC. Hearing sensitivity at 18 and 30 months correlated with PCC and explained 40% of the variation.

CONCLUSIONS

Mild HL impacted presence of CB at 10 months and was related to consonant proficiency at 36 months in children with HL associated with OME and children with cleft palate. The noncleft group showed results at 36 months similar to children with normal hearing; however, the CP±L group did not. Although the cleft palate may have a bigger impact on the speech development, management of hearing sensitivity would also be beneficial.

Assessment of prelinguistic vocalizations in real time: a comparison with phonetic transcription and assessment of inter-coder-reliability

This study investigated reliability of naturalistic listening in real time (NLRT) compared to phonetic transcription. Speech pathology students with brief training in NLRT assessed prelinguistic syllable inventory size and specific syllable types in typically developing infants. A second study also examined inter-coder reliability for canonical babbling, canonical babbling ratio and presence of oral stops in syllable inventory of infants with cleft palate, by means of NLRT. In study 1, ten students independently assessed prelinguistic samples of five 12-month-old typically developing infants using NLRT and phonetic transcription. Coders assessed syllable inventory size as more than twice as large using phonetic transcription as NLRT. Results showed a strong correlation between NLRT and phonetic transcription (syllables with more than five occurrences) for syllable inventory size (r = .60; p < .001). The methods showed similar results for inter-coder reliability of specific syllable types. In study 2, three other students assessed prelinguistic samples of twenty-eight 12-month-old infants with cleft palate by means of NLRT. Results revealed perfect inter-coder agreement for presence/absence of canonical babbling, strong correlations between the three coders' assessment of syllable inventory size (average r = .83; p < .001), but more inter-coder variability for agreement of specific syllable types. In conclusion, NLRT is a reliable method for assessing prelinguistic measures in infants with and without cleft palate with inter-coder agreement levels comparable to phonetic transcription for specific syllable types.

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.

Maternal object naming is less adapted to preterm infants' than to term infants' word mapping

BACKGROUND

Term infants learn word-object relations in their first year during multisensory interactions with caregivers. Although preterm infants often experience language delays, little is known about how caregivers contribute to their early word-object learning. The present longitudinal study compared maternal naming and word learning in these infant groups.

METHODS

Forty moderately preterm and 40 term infants participated at 6-9 and 12 months with their mothers. At each visit, mothers named two novel objects during play, and infants' learning was assessed using dynamic displays of the familiar and novel (mismatched) word-object relations. Infants' general cognitive, language, and motoric abilities were evaluated. Maternal multisensory naming was coded for synchrony between the target words and object motions and other naming styles.

RESULTS

During play, although overall maternal naming-style was similar across infant groups within visits, naming frequency increased to term but not preterm infants, from visit 1 to 2. On the test at visit 1, although the term infants' looked equally to novel and familiar word-object relations, their looking to the novel relations correlated positively with maternal synchrony use but inversely with naming frequency. At visit 2, term infants looked longer to the novel relations. In contrast, preterm infants showed no looking preference at either visit. Neither was their word-object learning correlated with maternal naming. Their cognition, language, and motor scores were attenuated when compared to term infants on the Bayley-III but not their MCDI vocabulary.

CONCLUSIONS

Less adaptive maternal naming and delayed word mapping in moderately preterm infants underscore a critical need for multisensory language intervention prior to first-word onset to alleviate its cascading effects on later language.

Acoustic properties of early vocalizations in infants with fragile X syndrome

Fragile X syndrome (FXS) is a neurogenetic syndrome characterized by cognitive impairments and high rates of autism spectrum disorder (ASD). FXS is often highlighted as a model for exploring pathways of symptom expression in ASD due to the high prevalence of ASD symptoms in this population and the known single-gene cause of FXS. Early vocalization features-including volubility, complexity, duration, and pitch-have shown promise in detecting ASD in idiopathic ASD populations but have yet to be extensively studied in a population with a known genetic cause for ASD such as FXS. Investigating early trajectories of these features in FXS may inform our limited knowledge of potential mechanisms that predict later social communication outcomes. The present study addresses this need by presenting preliminary findings which (a) characterize early vocalization features in FXS relative to low-risk controls (LRC) and (b) test the specificity of associations between these features and language and ASD outcomes. We coded vocalization features during a standardized child-examiner interaction for 39 nine-month-olds (22 FXS, 17 LRC) whose clinical outcomes were assessed at 24 months. Our results provide preliminary evidence that within FXS, associations between vocalization features and 24-month language outcomes may diverge from those observed in LRC, and that vocalization features may be associated with later ASD symptoms. These findings provide a starting point for more research exploring these features as potential early markers of ASD in FXS, which in turn may lead to improved early identification methods, treatment approaches, and overall well-being of individuals with ASD. Autism Res2019. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Although vocal features of 9-month-olds with FXS did not differ from those of low-risk controls, several features were associated with later language and ASD outcomes at 24 months in FXS. These preliminary results suggest acoustic data may be related to clinical outcomes in FXS and potentially other high-risk populations. Further characterizing these associations may facilitate understanding of biological mechanisms and risk factors associated with social communication development and ASD.

Canonical Babbling: A Marker for Earlier Identification of Late Detected Developmental Disorders?

Purpose of Review

To summarize findings about the emergence and characteristics of canonical babbling in children with late detected developmental disorders (LDDDs), such as autism spectrum disorder, Rett syndrome, and fragile X syndrome. In particular, we ask whether infants’ vocal development in the first year of life contains any markers that may contribute to earlier detection of these disorders.

Recent Findings

Only a handful studies have investigated canonical babbling in infants with LDDDs. With divergent research paradigms and definitions applied, findings on the onset and characteristics of canonical babbling are inconsistent and difficult to compare. Infants with LDDDs showed reduced likelihood to produce canonical babbling vocalizations. If achieved, this milestone was more likely to be reached beyond the critical time window of 5–10 months.

Summary

Canonical babbling appears promising as a potential marker for early detection of infants at risk for developmental disorders. In-depth studies on babbling characteristics in LDDDs are warranted.

Parents' contingent responses in communication with 10-month-old children in a clinical group with typical or late babbling

Parental responsive behaviour in communication has a positive effect on child speech and language development. Absence of canonical babbling (CB) in 10-month-old infants is considered a risk factor for developmental difficulties, yet little is known about parental responsiveness in this group of children. The purpose of the current study was to examine proportion and type of parental responsive utterances after CB and vocalization utterances respectively in a clinical group of children with otitis media with effusion, with or without cleft palate. Audio-video recordings of interactions in free play situations with 22 parents and their 10-month-old infants were used, where 15 infants had reached the CB stage and 7 infants had not. Fifty consecutive child utterances were annotated and categorized as vocalization utterance or CB utterance. The parent's following contingent response was annotated and labelled as acknowledgements, follow-in comments, imitations/expansions or directives. The Average intra-judge agreement was 90%, and the average inter-judger agreement was 84%. There was no significant difference in proportion contingent responses after vocalizations and CB, neither when considering all child utterances nor the child's babbling stage. However, imitations/expansions tended to be more common after CB in the typical babbling group, whereas acknowledgements were more common after CB in the late babbling group. Our findings imply that responsiveness is a supportive strategy that is not fully used by parents of children with late babbling. Implications for further research as well as parent-directed intervention for children in clinical groups with late babbling are suggested.

Language Origins Viewed in Spontaneous and Interactive Vocal Rates of Human and Bonobo Infants

From the first months of life, human infants produce "protophones," speech-like, non-cry sounds, presumed absent, or only minimally present in other apes. But there have been no direct quantitative comparisons to support this presumption. In addition, by 2 months, human infants show sustained face-to-face interaction using protophones, a pattern thought also absent or very limited in other apes, but again, without quantitative comparison. Such comparison should provide evidence relevant to determining foundations of language, since substantially flexible vocalization, the inclination to explore vocalization, and the ability to interact socially by means of vocalization are foundations for language. Here we quantitatively compare data on vocalization rates in three captive bonobo (Pan paniscus) mother-infant pairs with various sources of data from our laboratories on human infant vocalization. Both humans and bonobos produced distress sounds (cries/screams) and laughter. The bonobo infants also produced sounds that were neither screams nor laughs and that showed acoustic similarities to the human protophones. These protophone-like sounds confirm that bonobo infants share with humans the capacity to produce vocalizations that appear foundational for language. Still, there were dramatic differences between the species in both quantity and function of the protophone and protophone-like sounds. The bonobo protophone-like sounds were far less frequent than the human protophones, and the human protophones were far less likely to be interpreted as complaints and more likely as vocal play. Moreover, we found extensive vocal interaction between human infants and mothers, but no vocal interaction in the bonobo mother-infant pairs-while bonobo mothers were physically responsive to their infants, we observed no case of a bonobo mother vocalization directed to her infant. Our cross-species comparison focuses on low- and moderate-arousal circumstances because we reason the roots of language entail vocalization not triggered by excitement, for example, during fighting or intense play. Language appears to be founded in flexible vocalization, used to regulate comfortable social interaction, to share variable affective states at various levels of arousal, and to explore vocalization itself.

Relationship between mother-infant mutual dyadic responsiveness and premature infant development as measured by the Bayley III at 6 weeks corrected age

BACKGROUND

The quality of mother-preterm infant interaction has been identified as a key factor in influencing the infant's later development and language acquisition. The relationship between mother-infant responsiveness and later development may be evident early in infancy, a time period which has been understudied.

AIM

Describe the relationship between mother-infant mutual dyadic responsiveness and premature infant development.

DESIGN

This study employed a secondary analysis of data from the 6-week corrected age (CA) follow-up visit of the Hospital-Home Transition: Optimizing Prematures' Environment (H-HOPE) study, a randomized clinical trial testing the efficacy of a mother- and infant- focused intervention for improving outcomes among premature infants.

SUBJECTS

Premature infants born between 29 and 34 weeks gestational age and their mothers who had social-environmental risks.

OUTCOME MEASURES

At 6-weeks corrected age, a play session was coded for the quality of mutual responsiveness (Dyadic Mutuality Code). Development was assessed via the Bayley Scales of Infant and Toddler Development, 3rd edition.

RESULTS

Of 137 mother-infant dyads, high, medium and low mutual responsiveness was observed for 35.8%, 34.3% and 29.9%, respectively. Overall motor, language and cognitive scores were 115.8 (SD = 8.2), 108.0 (7.7) and 109.3 (7.9). Multivariable linear models showed infants in dyads with high versus low mutual responsiveness had higher scores on the motor (β = 3.07, p = 0.06) and language (β = 4.47, p = 0.006) scales.

CONCLUSION

High mutual responsiveness in mother-premature infant dyads is associated with significantly better language development and marginally better motor development.

The Implications of Nasal Substitutions in the Early Phonology of Toddlers With Repaired Cleft Palate

OBJECTIVE

To examine the implications of nasal substitutions in the early words of toddlers with cleft palate.

DESIGN

Retrospective.

PATIENTS

Thirty-four toddlers with nonsyndromic cleft palate and 20 noncleft toddlers, followed from ages 13 to 39 months.

MAIN OUTCOME MEASURES

The groups were compared for the percentage of toddlers who produced nasal substitutions in their early words. The percentage of toddlers with repaired cleft palate who produced nasal substitutions and were later suspected of having velopharyngeal dysfunction (VPD) was also examined.

RESULTS

Seventy-six percent of the toddlers in the cleft group (n = 26) and 35% of toddlers in the noncleft group (n = 7) produced nasal substitutions on one or more of their early words. Only 38% (10/26) of the toddlers with cleft palate who produced nasal substitutions in their early words were later diagnosed as having moderate-severe hypernasality and suspected VPD.

CONCLUSIONS

The presence of nasal substitutions following palatal surgery was not always an early sign of VPD. These substitutions were present in the early lexicon of children with and without cleft palate.

Babbling development as seen in canonical babbling ratios: A naturalistic evaluation of all-day recordings

Canonical babbling (CB) is critical in forming foundations for speech. Research has shown that the emergence of CB precedes first words, predicts language outcomes, and is delayed in infants with several communicative disorders. We seek a naturalistic portrayal of CB development, using all-day home recordings to evaluate the influences of age, language, and social circumstances on infant CB production. Thus we address the nature of very early language foundations and how they can be modulated. This is the first study to evaluate possible interactions of language and social circumstance in the development of babbling. We examined the effects of age (6 and 11 months), language/culture (English and Chinese), and social circumstances (during infant-directed speech [IDS], during infant overhearing of adult-directed speech [ADS], or when infants were alone) on canonical babbling ratios (CBR = canonical syllables/total syllables). The results showed a three-way interaction of infant age by infant language/culture by social circumstance. The complexity of the results forces us to recognize that a variety of factors can interact in the development of foundations for language, and that both the infant vocal response to the language/culture environment and the language/culture environment of the infant may change across age.

Phonetic Description of Babbling in Danish Toddlers Born with and without Unilateral Cleft Lip and Palate

Objective

To investigate prelinguistic vocalization sequences of 1-year-old children with and without cleft lip and palate.

Design

Prospective study.

Participants

Thirty-eight children born with unilateral cleft lip and palate and 36 control children born without clefts. The cleft children had the lip, soft palate, and posterior part of the hard palate repaired at 4 months of age. The lip was closed ad modum Millard, the nose was corrected according to McComb, and the soft palate was closed with a posteriorly based vomer flap.

Methods

Data were obtained from a clinical visit during which the baby played with the mother. Video recordings were transcribed and analyzed concerning (1) the frequency of occurrence of vocalization sequences, (2) the frequency of occurrence of contoids and vocoids, (3) the contoids’ place and manner of articulation, and (4) the percentage of children who entered the canonical babbling stage.

Results

No significant differences were observed between the cleft and control groups concerning frequency of occurrence of vocalization sequences, contoids, or vocoids. Structural differences between the groups seem to influence the contoid inventory, with a higher frequency of occurrence of nasal contoids and a smaller frequency of occurrence of alveolar contoids in the cleft group. Canonical babbling was achieved by most children in both groups, and no significant difference was found between the groups.

Conclusions

Early closure of the soft palate seems to have a positive influence on the prelinguistic development of children with cleft palate.

A Systematic Review of Speech Assessments for Children With Autism Spectrum Disorder: Recommendations for Best Practice

PURPOSE

The purpose of this systematic review was to provide a summary and evaluation of speech assessments used with children with autism spectrum disorders (ASD). A subsequent narrative review was completed to ascertain the core components of an evidence-based pediatric speech assessment, which, together with the results of the systematic review, provide clinical and research guidelines for best practice.

METHOD

A systematic search of eight databases was used to find peer-reviewed research articles published between 1990 and 2014 assessing the speech of children with ASD. Eligible articles were categorized according to the assessment methods used and the speech characteristics described.

RESULTS

The review identified 21 articles that met the inclusion criteria, search criteria, and confidence in ASD diagnosis. The speech of prelinguistic participants was assessed in seven articles. Speech assessments with verbal participants were completed in 15 articles with segmental and suprasegmental aspects of speech analyzed. Assessment methods included connected speech samples, single-word naming tasks, speech imitation tasks, and analysis of the production of words and sentences.

CONCLUSIONS

Clinical and research guidelines for speech assessment of children with ASD are outlined. Future comparisons will be facilitated by the use of consistent reporting methods in research focusing on children with ASD.

Babbling in children with neurodevelopmental disability and validity of a simplified way of measuring canonical babbling ratio

Babbling is an important precursor to speech, but has not yet been thoroughly investigated in children with neurodevelopmental disabilities. Canonical babbling ratio (CBR) is a commonly used but time-consuming measure for quantifying babbling. The aim of this study was twofold: to validate a simplified version of the CBR (CBR^UTTER), and to use this measure to determine if early precursors to speech and language development could be detected in children with different neurodevelopmental disabilities. Two different data sets were used. In Part I, CBR^UTTER was compared to two other CBR measures using previously obtained phonetic transcriptions of 3571 utterances from 38 audio recordings of 12-18 month old children with and without cleft palate. In CBR^UTTER, number of canonical utterances was divided by total number of utterances. In CBR^syl, number of canonical syllables was divided by total number of syllables. In CBR^utt, number of canonical syllables was divided by total number of utterances. High agreement was seen between CBR^UTTER and CBR^syl, suggesting CBR^UTTER as an alternative. In Part II, babbling in children with neurodevelopmental disability was examined. Eighteen children aged 12-22 months with Down syndrome, cerebral palsy or developmental delay were audio-video recorded during interaction with a parent. Recordings were analysed by observation of babbling, consonant production, calculation of CBR^UTTER, and compared to data from controls. The study group showed significantly lower occurrence of all variables, except for of plosives. The long-term relevance of the findings for the speech and language development of the children needs to be investigated.

Infants at-risk for autism spectrum disorder: Patterns of vocalizations at 14 months

Differences in the early development of children are crucial for early detection of autism spectrum disorder (ASD). Previous studies have shown large differences between children later diagnosed with ASD and their typically developing peers in the early use of canonical vocalizations (i.e., vocalizations that include well-formed consonant-vowel syllables) and the use of vocalizations for communicative purposes. In this prospective study, we examined the extent to which infant vocalizations at 14 months would predict Autism Diagnostic Observation Schedule (ADOS) diagnostic symptom groups, that is, Autism, Spectrum, and Non-ASD, for 82 community-identified at-risk infants at 23 months. Thirty-minute video samples were coded with the intention to categorize and quantify speech (canonical/noncanonical and directed/nondirected) and nonspeech vocalizations (atypical, distress, and pleasure vocalizations). Our results revealed that more canonical directed (OR = 1.039, P = .036), and fewer noncanonical directed (OR=.607, P = .002) and noncanonical nondirected (OR = 1.200, P = .049) vocalizations were associated with a greater likelihood of being in the Non-ASD group versus the Autism group, with no variables significantly predicting Autism versus Spectrum group membership. Despite some statistically significant findings, models performed poorly in classifying children into correct ASD symptom group at age 23 months based on vocalizations at 14 months. Thus, the utility of infant vocalizations alone for predicting toddler clinical outcomes among infants initially identified at an elevated risk for ASD appears limited; however, considering the structure and function of early vocalizations combined with other early developmental and behavioral features may improve the confidence for clinicians in making an early diagnosis of ASD. Autism Res 2017, 10: 1372-1383. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Volubility of the human infant: Effects of parental interaction (or lack of it)

Although parental volubility, or amount of talk, has received considerable recent attention, infant volubility has received comparatively little attention despite its potential significance for communicative risk status and later linguistic and cognitive outcomes. Volubility of 16 typically developing infants from 2 to 11 months of age was longitudinally investigated in the present study across three social circumstances: parent talking to infant, parent not talking to infant and parent talking to interviewer while the infant was in the room. Results indicated that volubility was least in the Interview circumstance. There were no significant differences in volubility between the parent Talk and No Talk circumstances. Volubility was found to reduce with age. These results suggest that infants vocalise in a variety of circumstances, even when no one talks to or interacts with them. The presence of a stranger or perhaps overhearing adults speaking to each other, however, may significantly reduce infant volubility.

Early communicative behaviors and their relationship to motor skills in extremely preterm infants

Despite the predictive value of early spontaneous communication for identifying risk for later language concerns, very little research has focused on these behaviors in extremely low-gestational-age infants (ELGA<28 weeks) or on their relationship with motor development. In this study, communicative behaviors (gestures, vocal utterances and their coordination) were evaluated during mother-infant play interactions in 20 ELGA infants and 20 full-term infants (FT) at 12 months (corrected age for ELGA infants). Relationships between gestures and motor skills, evaluated using the Bayley-III Scales were also examined. ELGA infants, compared with FT infants, showed less advanced communicative, motor, and cognitive skills. Giving and representational gestures were produced at a lower rate by ELGA infants. In addition, pointing gestures and words were produced by a lower percentage of ELGA infants. Significant positive correlations between gestures (pointing and representational gestures) and fine motor skills were found in the ELGA group. We discuss the relevance of examining spontaneous communicative behaviors and motor skills as potential indices of early development that may be useful for clinical assessment and intervention with ELGA infants.

Delay in auditory behaviour and preverbal vocalization in infants with unilateral hearing loss

AIM

To evaluate the impact of unilateral hearing loss (UHL) on early aural/oral communication skills of infants by comparing performance to infants with bilateral normal hearing (BNH).

METHOD

Thirty-four infants with UHL (median age 9.4mo, 25th-75th centile 7.34-12.15) and 331 control infants with BNH (median age 9mo, 6.0-13.38) were divided into two subgroups based on risk factors known to cause developmental delay: low risk and high risk. Early auditory skills and preverbal vocalizations were assessed using two parent questionnaires: the Infant-Toddler Meaningful Auditory Integration Scale and the Production of Infants Scale Evaluation.

RESULTS

Of the infants with UHL, 21% showed delays in auditory behaviour and 41% delays in preverbal vocalizations, compared to their peers with BNH (p<0.01). After adjusting for risk level, delayed auditory behaviour and preverbal vocalizations were approximately four and nine times more common in infants with UHL compared to BNH respectively (p<0.01).

INTERPRETATION

This is the first study to show that infants with UHL are at higher risk of delay in early aural/oral communication abilities compared to infants with BNH even in the absence of other known risk factors for developmental delay. This has important implications for early intervention and habilitation of infants with UHL, in order to reduce some of the negative long-term consequences of what was once considered 'minor' hearing loss.

Vocal patterns in infants with autism spectrum disorder: canonical babbling status and vocalization frequency

Canonical babbling is a critical milestone for speech development and is usually well in place by 10 months. The possibility that infants with autism spectrum disorder (ASD) show late onset of canonical babbling has so far eluded evaluation. Rate of vocalization or "volubility" has also been suggested as possibly aberrant in infants with ASD. We conducted a retrospective video study examining vocalizations of 37 infants at 9-12 and 15-18 months. Twenty-three of the 37 infants were later diagnosed with ASD and indeed produced low rates of canonical babbling and low volubility by comparison with the 14 typically developing infants. The study thus supports suggestions that very early vocal patterns may prove to be a useful component of early screening and diagnosis of ASD.

Automated analysis of child phonetic production using naturalistic recordings

PURPOSE

Conventional resource-intensive methods for child phonetic development studies are often impractical for sampling and analyzing child vocalizations in sufficient quantity. The purpose of this study was to provide new information on early language development by an automated analysis of child phonetic production using naturalistic recordings. The new approach was evaluated relative to conventional manual transcription methods. Its effectiveness was demonstrated by a case study with 106 children with typical development (TD) ages 8-48 months, 71 children with autism spectrum disorder (ASD) ages 16-48 months, and 49 children with language delay (LD) not related to ASD ages 10-44 months.

METHOD

A small digital recorder in the chest pocket of clothing captured full-day natural child vocalizations, which were automatically identified into consonant, vowel, nonspeech, and silence, producing the average count per utterance (ACPU) for consonant and vowel.

RESULTS

Clear child utterances were identified with above 72% accuracy. Correlations between machine-estimated and human-transcribed ACPUs were above 0.82. Children with TD produced significantly more consonants and vowels per utterance than did other children. Children with LD produced significantly more consonants but not vowels than did children with ASD.

CONCLUSION

The authors provide new information on typical and atypical language development in children with TD, ASD, and LD using an automated computational approach.

Preterm and term infants’ perception of temporally coordinated syllable–object pairings: implications for lexical development

PURPOSE

This experimental study examined term infants (n = 34) and low-risk near-term preterm infants (gestational age 32–36 weeks) at 2 months chronological age (n = 34) and corrected age (n =16). The study investigated whether the preterm infants presented with a delay in their sensitivity to synchronous syllable–object pairings when compared with term infants.

METHOD

First, infants were habituated to a single syllable, [tah] or [gah], spoken in synchrony with the motions of 1 of 4 toy objects, a crab, a porcupine, a star, or a lamb chop. Next, the infants received 2 syllable- and 2 object-change test trials, counterbalanced for order.

RESULTS

After factoring out differential looking time during habituation, the study found that preterm infants showed attenuated looks to the change in the object and the change in the syllable relative to term infants.

CONCLUSIONS

These findings suggest that even near-term preterm infants present with a delay in their sensitivity to synchrony in syllable–object pairings relative to term infants. Given the important role that synchrony plays in word mapping at 6–9 months, this early delay in sensitivity to synchrony might be an indicator of word mapping delays found in older preterm infants.

Effects of social games on infant vocalizations*

The aim of the present study was to examine the contextual effects of social games on prelinguistic vocalizations. The two main goals were to (1) investigate the functions of vocalizations as symptoms of affective arousal and symbols of social understanding, and (2) explore form-function (de)coupling relations between vocalization types and game contexts. Seventy-one six-month-olds and sixty-four twelve-month-olds played with their mothers in normal and perturbed tickle and peek-a-boo games. The effects of infant age, game, game climax, and game perturbation on the frequency and types of infant vocalizations were examined. Results showed twelve-month-olds vocalized more mature canonical syllables during peek-a-boo and more primitive quasi-resonant nuclei during tickle than six-month-olds. Six- and twelve-month-olds increased their vocalizations from the set-up to climax during peek-a-boo, but they did not show such an increase during tickle. Findings support the symptom function of prelinguistic vocalizations reflecting affective arousal and the prevalence of form-function decoupling during the first year of life.

Early vocabulary in full term and preterm Estonian children

BACKGROUND

Preterm birth is considered to be a high risk factor for child development and early vocabulary can be used as an indicator for later development.

AIMS

The aim of the present study is to compare the size of early vocabulary, proportional use of different word categories, and mean length of utterance (henceforth MLU) of preterm and full term children.

METHOD

The sample consisted of 40 preterm (corrected ages 16-25 months) and two matched groups of full term children. First full term group consisted of 120 children who were matched by age and gender. Second full term group consisted of 109 children who were matched by age, gender and size of productive vocabulary. The data for this study were gathered using the Estonian adaptation of MacArthur-Bates Communicative Development Inventory: Words and Sentences.

RESULTS

Full term children who were matched by age and gender had larger vocabulary as compared to the preterm children's vocabulary (U = 1758.5, p = 0.01). Poisson regression yielded that age, gender, and preterm birth explained significantly the variance in the vocabulary size. Poisson regressions showed that all three variables explained significantly variance in proportional use of social terms and predicates. Age had significant effect for proportional use of common nouns. Age and preterm birth had a significant effect on the proportional use of function words. MLU was shorter in preterm than in full term children (U = 1125.0, p = 0.002).

CONCLUSIONS

Estonian preterm children's vocabulary is slightly smaller than full term children's vocabulary. There is a difference in the proportions of word categories used, as preterm children use more social terms, and less predicates, and function words.

Effects of environmental stimulation on infant vocalizations and orofacial dynamics at the onset of canonical babbling

The vocalizations and jaw kinematics of 30 infants aged 6-8 months were recorded using a Motion Analysis System and audiovisual technologies. This study represents the first attempt to determine the effect of play environment on infants' rate of vocalization and jaw movement. Four play conditions were compared: watching videos, social contingent reinforcement and vocal modeling with an adult, playing alone with small toys, and playing alone with large toys. The fewest vocalizations and spontaneous movement were observed when infants were watching videos or interacting with an adult. Infants vocalized most when playing with large toys. The small toys, which naturally elicited gross motor movement (e.g., waving, banging, shaking), educed fewer vocalizations. This study was also the first to quantify the kinematics of vocalized and non-vocalized jaw movements of 6-8 month-old infants. Jaw kinematics did not differentiate infants who produced canonical syllables from those who did not. All infants produced many jaw movements without vocalization. However, during vocalization, infants were unlikely to move their jaw. This contradicts current theories that infant protophonic vocalizations are jaw-dominant. Results of the current study can inform socio-linguistic and kinematic theories of canonical babbling.

How to measure the onset of babbling reliably?

Various measures for identifying the onset of babbling have been proposed in the literature, but a formal definition of the exact procedure and a thorough validation of the sample size required for reliably establishing babbling onset is lacking. In this paper the reliability of five commonly used measures is assessed using a large longitudinal corpus of spontaneous speech from forty infants (age 0 ; 6-2 ; 0). In a first experiment it is shown that establishing the onset of babbling with reasonable (95%) confidence is impossible when the measures are computed only once, and when the number of vocalizations are not equal for all children at all ages. In addition, each measure requires a different minimal sample size. In the second experiment a robust procedure is proposed and formally defined that permits the identification of the onset of babbling with 95% confidence. The bootstrapping procedure involves extensive resampling and requires relatively few data.

Development and predictive value of early vocalizations in very-low-birth-weight children: a longitudinal study

The aim of the present study was to analyze early vocalization development, the predictive value of this development in terms of later language skills, and possible gender difference in early vocalization development in a selected cohort of 32 very-low-birth-weight (VLBW) children and 35 full-term controls. The data on early vocalization development were gathered using a structured maternal report method. Language skills were assessed at 2.0. No significant difference was found between the groups in the rate of early vocalization development when corrected age was used for the VLBW children. The rate of early vocalization development correlated significantly with later language performance in VLBW children. Only weak correlations were detected in the control group. We found no gender difference in early vocalization development in either of the groups. The findings suggest that the rate of early vocalization development can be used as a clinical predictor of later linguistic performance in VLBW children.

Early vocalization of preterm infants with extremely low birth weight (ELBW), Part II: From canonical babbling up to the appearance of the first word

The aim of this study was to systematically describe the preverbal development of preterm infants from canonical babbling up to the first word and to compare it with that of healthy full-term infants. In addition, the amount of vocalization between the preterm and full-term groups was compared. The sample consisted of 18 preterm infants with extremely low birth weight and 11 full-term infants. The development of preverbal vocalization before variegated babbling did not differ between the groups. Instead, the preterm infants failed to produce more different kinds of canonical syllable types than the full-term infants. However, they showed a larger variance of variegated babbling skills and remained in the babbling phase longer before reaching the first meaningful word compared with the full-term infants. Following the onset of canonical babbling, the preterm infants produced fewer vocalizations than the full-term infants and they reached the first word later than the full-term infants.

An analysis of the frame-content theory in babble of 9-month-old babies with cleft lip and palate

The aim of this study was to examine the consonant-vowel co-occurrence patterns predicted by the Frame-Content theory in 16 nine-month-old babies with unrepaired cleft palate (±cleft lip) and 16 age-matched non-cleft babies. Babble from these babies was phonetically transcribed and grouped according to the intrasyllabic predictions of the theory (labial-central, alveolar-front, and velar-back). Both groups demonstrated the three consonant-vowel co-occurrence patterns predicted by the Frame-Content theory. Other patterns not predicted by the Frame-Content theory emerged as strong patterns as well.

LEARNING OUTCOMES

The reader will be able to: • Describe consonant-vowel co-occurrence patterns produced by babies with and without cleft palate. • Describe vowel inventories of babies with cleft palate. • Identify possible therapy targets for babies with cleft palate.

Early Consonant Production in Swedish Infants with and without Unilateral Cleft Lip and Palate and Two-Stage Palatal Repair

Objective

To investigate consonant production at 12 and 18 months of age following early soft palate repair in infants with unilateral cleft lip and palate (UCLP), and to compare it with typically developing children without clefts.

Design

Randomized study with comparison group.

Participants

Twenty Swedish infants born with UCLP and 21 without clefts (COMP) were included in a randomized trial of palatal surgery (Scandcleft project). Soft palate closure was completed at age 5 months; hard palate closure was performed in 11 of the infants with UCLP at 1 year of age (HPC) and was left open in nine (HPO).

Method

Audio recordings at 12 months (UCLP = 9, COMP = 21) and at 18 months (UCLP = 18, COMP = 21) were phonetically transcribed. Consonant inventory, frequency of manner and place of articulation, true canonical babbling (TCB), and impact of hearing status were analyzed.

Results

At 12 months of age, all children had reached the stage of TCB. Mild hearing impairment was significantly correlated with fewer consonant types. A lower frequency of dentals and oral stops was found in the UCLP group than in the COMP group. However, the number of oral stops was high compared with what has been previously reported.

Conclusions

Early soft palate closure seems to give a relatively high number of oral stops even with the hard palate unrepaired, although with significantly fewer dentals/alveolars than are seen in peers without clefts. Differences in consonant inventory were correlated with hearing function.

The prelexical development in children implanted by 16 months compared with normal hearing children

OBJECTIVE

Few studies exist which document the early speech development of German-speaking children or German-speaking children who are deaf and using cochlear implants. The current study aims to: (1) document the pre-canonical and canonical speech development of German-speaking children who are deaf and receive cochlear implants by the age of 16 months and (2) compare these children's results with those of children with normal hearing.

DESIGN

This longitudinal study included 5 German-speaking children with normal hearing and 5 with sensorineural deafness. All children from the deaf group received hearing amplification before cochlear implantation, received their first implant by 16 months of age, and became bilateral implant users by 31 months of age. The pre-canonical and canonical vocalisations of each child were recorded on video- and audiotapes in a semi-standardised playing situation every 4 weeks over a span of 1 year. In the cochlear implant group, the recording started 4-5 days postoperatively (first implant); in the normal hearing group it began between the ages of 4 and 5 months. The video and audio recordings were analysed using EUDICO Linguistic Annotator version 2.4 (Nijmegen, The Netherlands) and International Phonetic Alphabet transcription.

RESULTS

Both groups showed individual patterns of babbling acquisition, though the groups' patterns of acquisition were similar when analysed for consonant manner and place. Some children started with plosives and others, with nasals, but all acquired fricatives and laterals next. Onset of canonical babbling for children in the cochlear implant group began 0-4 months after first fitting of the first device, while children from the normal hearing group demonstrated an onset of canonical babbling between 4 and 9 months of age.

CONCLUSION

Our results show that deaf children who receive cochlear implants at an early age are capable of reaching the canonical babbling milestone in a shorter time than children with normal hearing typically do and that their consonant phoneme acquisition follows a similar sequence to normal hearing peers'. These results are consistent with the literature indicating that early identification and intervention are important for allowing children with cochlear implants the opportunity to catch up to hearing peers.

Mean Length of Utterance before words and grammar: longitudinal trends and developmental implications of infant vocalizations

This study measured longitudinal change in six parameters of infant utterances (i.e. number of sounds, CV syllables, supraglottal consonants, and repetitions per utterance, temporal duration, and seconds per sound), investigated previously unexplored characteristics of repetition (i.e. number of vowel and CV syllable repetitions per utterance) and analyzed change in vocalizations in relation to age and developmental milestones using multilevel models. Infants (N=18) were videotaped bimonthly during naturalistic and semi-structured activities between 0 ; 3 and the onset of word use (M=11.8 months). Results showed that infant utterances changed in predictable ways both in relation to age and in relation to language milestones (i.e. reduplicated babble onset, word comprehension and word production). Looking at change in relation to the milestones of language development led to new views of babbling, the transition from babbling to first words, and processes that may underlie these transitions.

[Early hearing experience and sensitive developmental periods]

This article reviews the studies on functional deficits in the auditory cortex of congenitally deaf animals. It compares their results with psychophysical and imaging data obtained from prelingually deaf humans. The studies demonstrate that the development of the auditory cortex is affected by the absence of hearing experience. In humans, the restoration of hearing after congenital deafness shows a sensitive period of 4 years, whereas even within this sensitive period cortical plasticity is already decreasing with increasing age. The reasons for the sensitive period are developmental changes of synaptic plasticity, developmentally modified synaptogenesis and synaptic pruning as well as changes in connectivity of the auditory cortex. Absence of top-down interactions from higher order auditory areas is another cardinal reason for the sensitive period. All these mechanisms contribute to the decreasing capacity for cortical plasticity during postnatal development. From the developmental and neurophysiological point of view, an early identification of hearing loss is an important prerequisite for effective therapy.

Fundamental frequency development in typically developing infants and infants with severe-to-profound hearing loss

Little research has been conducted on the development of suprasegmental characteristics of vocalizations in typically developing infants (TDI) and the role of audition in the development of these characteristics. The purpose of the present study was to examine the longitudinal development of fundamental frequency (F(0)) in eight TDI and eight infants with severe-to-profound hearing loss matched for level of vocal development. Results revealed no significant changes in F(0) with advances in pre-language vocal development for TDI. Infants with hearing loss, however, showed a statistically reliable higher variability of F(0) than TDI, when age was accounted for as a covariate. The results suggest development of F(0) may be strongly influenced by audition.

On the robustness of vocal development: an examination of infants with moderate-to-severe hearing loss and additional risk factors

PURPOSE

Onset of canonical babbling by 10 months of age is surprisingly robust in infancy, suggesting that there must be deep biological forces that keep the development of this key vocal capability on course. This study further evaluated the robustness of canonical babbling and other aspects of prelinguistic vocal development.

METHOD

Longitudinal observation was conducted on 4 infants who were at risk for abnormal vocal development because of bilateral moderate-to-severe sensorineural hearing loss and additional risk factors for developmental delay.

RESULTS

Two of the infants were delayed in the onset of canonical babbling and showed greater fluctuation in canonical babbling ratios following its onset than did typically developing infants. On the same measures, the remaining 2 infants were within normal limits, although their age of onset for canonical babbling was later than the mean for typically developing infants. Volubility was not notably different from typically developing infants. Differences from typically developing infants were, however, observed in proportions of various prelinguistic syllable types produced across time.

CONCLUSION

Results provided further evidence of robustness of canonical babbling and indicated the need for a large parametric study evaluating effects of varying degrees of hearing loss and other risk factors on vocal development.

Predicting phonetic transcription agreement: insights from research in infant vocalizations

The purpose of this study is to provide new perspectives on correlates of phonetic transcription agreement. Our research focuses on phonetic transcription and coding of infant vocalizations. The findings are presumed to be broadly applicable to other difficult cases of transcription, such as found in severe disorders of speech, which similarly result in low reliability for a variety of reasons. We evaluated the predictiveness of two factors not previously documented in the literature as influencing transcription agreement: canonicity and coder confidence. Transcribers coded samples of infant vocalizations, judging both canonicity and confidence. Correlation results showed that canonicity and confidence were strongly related to agreement levels, and regression results showed that canonicity and confidence both contributed significantly to explanation of variance. Specifically, the results suggest that canonicity plays a major role in transcription agreement when utterances involve supraglottal articulation, with coder confidence offering additional power in predicting transcription agreement.