Does prosody make the difference? A meta-analysis on relations between prosodic aspects of infant-directed speech and infant outcomes

Acoustic Exaggeration Enhances Speech Discrimination in Young Autistic Children

Child-directed speech (CDS), which amplifies acoustic and social features of speech during interactions with young children, promotes typical phonetic and language development. In autism, both behavioral and brain data indicate reduced sensitivity to human speech, which predicts absent, decreased, or atypical benefits of exaggerated speech signals such as CDS. This study investigates the impact of exaggerated fundamental frequency (F0) and voice-onset time on the neural processing of speech sounds in 22 Chinese-speaking autistic children aged 2-7 years old with a history of speech delays, compared with 25 typically developing (TD) peers. Electroencephalography (EEG) data were collected during passive listening to exaggerated and non-exaggerated syllables. A time-resolved multivariate pattern analysis (MVPA) was used to evaluate the potential effects of acoustic exaggeration on syllable discrimination in terms of neural decoding accuracy. For non-exaggerated syllables, neither the autism nor the TD group achieved above-chance decoding accuracy. In contrast, for exaggerated syllables, both groups achieved above-chance decoding, indicating significant syllable discrimination, with no difference in accuracy between the autism and TD groups. However, the temporal generalization patterns in the MVPA results revealed distinct neural mechanisms supporting syllable discrimination between the groups. Although the TD group demonstrated a left-hemisphere advantage for decoding and generalization, the autism group displayed similar decoding patterns between hemispheres. These findings highlight the potential of selective acoustic exaggeration to support speech learning in autistic children, underscoring the importance of tailored, sensory-based interventions.

Evaluation of the Early Development of 6-Month-Old Babies in the Case of Maternal Postpartum Depression with or Without Bipolar Disorder

BACKGROUND

The first year of life is the period of greatest brain plasticity. Postpartum depression can adversely affect the first interactions with the child and, consequently, their emotional, social, and cognitive development.

OBJECTIVES

First, to describe the developmental profile of six-month-old infants of mothers suffering from severe postpartum depression, and, second, to compare the development of infants whose mothers suffer from depression with or without bipolar disorder.

METHODS

This is a retrospective descriptive study on 6-month-old babies hospitalized with their mothers at the Marseille Mother-Baby Unit (MBU) for maternal postpartum depression with or without bipolar disorder. Mothers were clinically diagnosed by a psychiatrist specialized in postpartum depression using the DSM-5; infant development was assessed at 6 months by an independent health professional using the revised Brunet-Lézine Scale, which allowed the calculation of global and partial developmental quotients (DQ).

RESULTS

We followed 40 mother-infant dyads. None of the 40 infants had a global developmental delay. However, maternal depression was significantly associated with poorer sociability (mean sociability DQ score of 94 ± 9.6, p < 0.001) and lower postural development (mean postural DQ score of 96.2 ± 8.9 *, p < 0.001) in the infants at 6 months of age. Postural development was significantly lower in children of bipolar mothers than in children of non-bipolar mothers (p = 0.03).

CONCLUSIONS

Postpartum depression was associated with a weakness in sociability and posture at the age of 6 months, without relevant developmental delay. Screening infants at an early age with specific tools allows for earlier intervention, which would positively influence their developmental trajectory.

A longitudinal investigation of the acoustic properties of infant-directed speech from 6 to 18 months

Caregivers often modulate their speech when interacting with infants, adapting a register that has been suggested to have attentional, affective and didactic purposes. The present preregistered study examined the longitudinal trajectories of a diverse range of acoustic features of infant-directed speech (IDS) and compared these with adult-directed speech (ADS), in Norwegian parents of 6- to 18-month-old infants. Sixty-nine families participated. Throughout five laboratory visits across one year, parents were recorded reading a picture-book to their infant (IDS) and an experimenter (ADS). The book was designed to tightly control for the linguistic content and context of speech between participants, timepoints and registers. Analyses of a total of 54 594 vowels and 22 958 phrases revealed, first, an overall effect of register: parents used higher pitch, wider pitch range, slower articulation rate, longer vowel duration and more variable and less distinct vowels in IDS than in ADS. Second, significant register-by-age interactions indicated that parents' IDS, compared with their ADS, featured wider pitch range, larger vowel space and shorter vowel duration in older as compared with younger infants, while pitch, articulation rate and vowel variability and distinctiveness remained relatively stable with age. Results are discussed in the context of the proposed functions of IDS.

The role of lexical and prosodic characteristics of mothers' child-directed speech for the early vocabulary development of Italian children with cochlear implants

BACKGROUND

Variability in the vocabulary outcomes of children with cochlear implants (CIs) is partially explained by child-directed speech (CDS) characteristics. Yet, relatively little is known about whether and how mothers adapt their lexical and prosodic characteristics to the child's hearing status (before and after implantation, and compared with groups with normal hearing (NH)) and how important they are in affecting vocabulary development in the first 12 months of hearing experience.

AIMS

To investigate whether mothers of children with CIs produce CDS with similar lexical and prosodic characteristics compared with mothers of age-matched children with NH, and whether they modify these characteristics after implantation. In addition, to investigate whether mothers' CDS characteristics predict children's early vocabulary skills before and after implantation.

METHODS & PROCEDURES

A total of 34 dyads (17 with NH, 17 with children with CIs; ages = 9-32 months), all acquiring Italian, were involved in the study. Mothers' and children's lexical quantity (tokens) and variety (types), mothers' prosodic characteristics (pitch range and variability), and children's vocabulary skills were assessed at two time points, corresponding to before and 1 year post-CI activation for children with CIs. Children's vocabulary skills were assessed using parent reports; lexical and prosodic characteristics were observed in semi-structured mother-child interactions.

OUTCOMES & RESULTS

Results showed that mothers of children with CIs produced speech with similar lexical quantity but lower lexical variety, and with increased pitch range and variability, than mothers of children with NH. Mothers generally increased their lexical quantity and variety and their pitch range between sessions. Children with CIs showed reduced expressive vocabulary and lower lexical quantity and variety than their peers 12 months post-CI activation. Mothers' prosodic characteristics did not explain variance in children's vocabulary skills; their lexical characteristics predicted children's early vocabulary and lexical outcomes, especially in the NH group, but were not related to later language development.

CONCLUSIONS & IMPLICATIONS

Our findings confirm previous studies on other languages and support the idea that the lexical characteristics of mothers' CDS have a positive effect on children's early measures of vocabulary development across hearing groups, whereas prosodic cues play a minor role. Greater input quantity and quality may assist children in the building of basic language model representations, whereas pitch cues may mainly serve attentional and emotional processes. Results emphasize the need for additional longitudinal studies investigating the input received from other figures surrounding the child and its role for children's language development.

WHAT THIS PAPER ADDS

What is already known on the subject Mothers' CDS is thought to facilitate and support language acquisition in children with various language developmental trajectories, including children with CIs. Because children with CIs are at risk for language delays and have acoustic processing limitations, their mothers may have to produce a lexically simpler but prosodically richer input, compared to mothers of children with NH. Yet, the literature reports mixed findings and no study to our knowledge has concurrently addressed the role of mothers' lexical and prosodic characteristics for children's vocabulary development before implantation and in the first 12 months of hearing experience. What this study adds to the existing knowledge The study shows that mothers of children with CIs produce input of similar quantity but reduced variety, and with heightened pitch characteristics, compared to mothers of children with NH. There was also a general increase in mothers' lexical quantity and variety, and in their pitch range, between sessions. Only their lexical characteristics predicted children's early vocabulary skills. Their lexical variety predicted children's expressive vocabulary and lexical variety only in the NH group. What are the practical and clinical implications of this work? These findings expand our knowledge about the effects of maternal input and may contribute to the improvement of early family-centred intervention programmes for supporting language development in children with CIs.

Paternal and Maternal Speech at 3 Months Postpartum: An Exploratory Study on the Effect of Parental Role and Birth Weight

Recent research highlights a growing interest in early interactions between fathers and their infants, acknowledging the significant influence these interactions have on developmental outcomes. However, there is a limited understanding of the specific characteristics of paternal infant-directed speech (IDS), especially in the context of premature birth. This study aimed to analyze the functional and morpho-syntactic features of paternal IDS to full-term (FT) and preterm (PT) infants at 3 months, comparing it with maternal communicative style. Additionally, the study explored the influence of the severity of preterm birth according to birth weight, further distinguishing between extremely low-birth-weight (ELBW) and very low-birth-weight (VLBW) infants. Seventy-one father-infant and mother-infant dyads (24 FT, 22 ELBW, 25 VLBW) were recruited at 3 months (corrected age for PTs). Parent-infant interactions were video recorded to assess lexical, syntactic, and functional aspects of paternal and maternal speech. Results revealed lower verbosity and lexical variability in paternal IDS compared to the maternal one. No differences were found between parents of the PT and FT groups. Overall, these findings could contribute to better understanding the patterns of parent-infant communications in both FT and PT dyads, confirming the importance of involving both mothers and fathers from the early stages of development.

Improving Infant Mental Health: A Pilot Study on the Effectiveness, Acceptability and Feasibility of Eye Movement Desensitization and Reprocessing (EMDR) Storytelling in Infants With Post-traumatic Distress After Medical Procedures

Although the prevalence of symptoms of post-traumatic stress disorder (PTSD) in infants and young children is similar as in older age groups, and PTSD intervention is as important in this age group, research on PTSD-treatment in infants is very scarce. Eye Movement Desensitization and Reprocessing (EMDR) Storytelling is a trauma-focused treatment that is being used by clinicians for infants with PTSD-symptoms. The aim was to assess the feasibility, acceptability and initial indications of effectiveness of EMDR Storytelling for infants aged 3-24 months with PTSD-symptoms after medical procedures. We included 6 infants and administered personalized items to assess PTSD-symptoms during the baseline, intervention and follow-up phase on a day-to-day basis. Furthermore, we measured PTSD-classification and symptoms at three and four measurement points, respectively. The data was analysed visually and quantitatively. EMDR Storytelling was shown to be feasible and acceptable for all participating families. Parent- and therapist-report showed that four out of the six infants included in the current study showed a clear reduction over time in PTSD-classification, -symptoms, and daily measured PTSD-symptoms. The results concerning the other two infants were mixed. Attention should be paid to cognitive (language) as well as interactional (infant-parent) mechanisms potentially underlying the benefits of EMDR Storytelling.

Testing the relationship between preferences for infant-directed speech and vocabulary development: A multi-lab study

From early on, infants show a preference for infant-directed speech (IDS) over adult-directed speech (ADS), and exposure to IDS has been correlated with language outcome measures such as vocabulary. The present multi-laboratory study explores this issue by investigating whether there is a link between early preference for IDS and later vocabulary size. Infants' preference for IDS was tested as part of the ManyBabies 1 project, and follow-up CDI data were collected from a subsample of this dataset at 18 and 24 months. A total of 341 (18 months) and 327 (24 months) infants were tested across 21 laboratories. In neither preregistered analyses with North American and UK English, nor exploratory analyses with a larger sample did we find evidence for a relation between IDS preference and later vocabulary. We discuss implications of this finding in light of recent work suggesting that IDS preference measured in the laboratory has low test-retest reliability.

Investigation of mothers' elicited infant-directed speech and singing for preterm infants

BACKGROUND

Mother's voice is a salient auditory stimulus commonly experienced during early development; after birth, characteristic acoustic modulations of mothers' infant-directed speech (IDSpeech) and singing (IDSinging) contribute to neurodevelopment. For preterm infants, early separation leads to decreased exposure to mother's voice; the impact on maternal ability to produce IDSpeech/IDSinging and infant perception of mother's voice is unknown.

METHODS

Fifty mother/preterm-infant dyads were enrolled in this prospective cohort study. Forty-four mothers recorded Twinkle, Twinkle Little Star in coached adult-directed speech (ADSpeech), IDSpeech, and IDSinging. Between 34.0-36.9w CGA, infants underwent high-density EEG during exposure to their mother's voice recordings. Acoustic features of mothers' voice and infant cortical response were analyzed and correlated.

RESULTS

Acoustic features of recorded maternal ADSpeech, IDSpeech, and IDSinging were significantly different. In 33 infants with EEG, mean fundamental frequency and speech production rate (SPR) variability correlated with infant responses to ADSpeech; SPR and SPR variability correlated with IDSpeech; SPR correlated with IDSinging. Correlations were found at differing scalp locations for speech versus singing.

CONCLUSION

Mothers of hospitalized preterm infants differentially modulate their voice during coached recorded language; features can then be differentiated by their preterm infants thus presenting opportunities for targeted interventions when parents cannot be present.

IMPACT

Mothers of preterm infants can record their voice with acoustically quantifiable characteristics of infant-directed singing and speech, even when not at their infant's bedside. Recorded adult- and infant-directed speech stimuli are differentially processed in the brains of hospitalized preterm infants. The ability for mothers to create acoustically-distinct infant-directed speech in the absence of their infant may be driven by coaching to achieve an approximated sense of connection with their infant.

Cortical Responses to Mother's Voice in Comparison with Unfamiliar Voice in the First Trimester of Life: A fNIRS Study

Introduction  The use of functional near-infrared light spectroscopy (fNIRS) may be applied to study cortical responses in children and could offer insight into auditory and speech perception during the early stages of life. Some literature suggests that babies are already able to identify familiar voices at birth, and fNIRS is a non-invasive technique that can be used to study this population. Objective  To characterize the cortical responses of infants during their first trimester of life to infant-directed speech using near-infrared light spectroscopy and to verify whether there is a difference in responses when infant-directed speech is performed by their mother compared with an unknown person. Methods  Twenty-three children between 0 and 3 months, healthy, without risk indicators for hearing loss, and with results considered normal in the audiological evaluation were tested with near-infrared spectroscopy using infant-directed speech as an auditory stimulus produced by their own mother and by an unknown source. Results  Bilateral cortical activation was observed. The responses were present in the temporal, frontal, and parietal regions. Regarding the familiarity aspect, no significant difference was observed for the mother's voice compared with an unknown voice. Conclusion  Infant-directed speech has prosodic characteristics capable of activating several cortical regions in the infant's first trimester of life, especially the temporal region. The familiarity effect needs to be better defined for this type of stimulus during this period.

Processing of visual stimuli following infant directed speech: Attention-guiding effects of unfamiliar speech

This study investigates attention modulation as a function of infant directed (ID) versus adult directed (AD) speech in seven-month-old infants using electroencephalographic measures. In three experiments, infants were presented with either ID speech or AD speech as stimuli, followed by highly variable images of inanimate objects as targets. In Experiment 1 (N = 18), images were preceded by ID or AD speech with semantic content ("Look here"). Contrary to hypothesis, targets preceded by AD speech elicited increased amplitude of the Negative central (Nc) component compared to targets preceded by ID speech, indicating increased attention. Experiment 2 (N = 23) explored whether ID versus AD speech influences attention allocation also without semantic content. The same targets were either preceded by human voice sounds without semantic content ("Uh-Ah") following the prosody of either ID or AD speech register. No differences in attention allocation or object processing were observed. Experiment 3 (N = 18) contrasted ID speech with and without semantic content and found enhanced attention allocation following stimuli without semantic content, but increased object processing following stimuli with semantic content. Overall, the effects observed here are consistent with the idea that less familiar speech stimuli increase attention for subsequent objects. Semantic content of stimuli increased the depth of object processing in 7-month-olds.

Maternal input to 24-month-old children with sex chromosome trisomies

BACKGROUND

Maternal input plays an important role in influencing linguistic development during the first years of life, and it is evident that mothers adapt their language according to their child's characteristics. Recently, it was demonstrated that maternal input addressed to children with sex chromosome trisomies (SCTs) at 8 months of age is prosodically and functionally different from that addressed to typically developing (TD) peers.

AIMS

The study aimed at analysing maternal input at 24 months when the presence of a language delay could be more evident than during the preverbal stage. We were interested in examining if maternal input was influenced by a diagnosis of SCT (by comparing children with SCT and TD children) or by children's linguistic level (by comparing children with weak lexical ability versus children with typical lexical ability regardless of the presence of genetic diagnosis).

METHODS AND PROCEDURES

Forty-four mother-child dyads in which the children had an SCT and 20 mother-child dyads in which the children were TD participated in the study. Of these 64 dyads, 23 children (21 with SCTs and two TD children) formed the group of children with weak lexical ability (children with a vocabulary size lower than 50 words at 24 months). Maternal utterances were collected during one video-recorded play session and were then coded considering both the linguistic and functional features of the input.

OUTCOMES AND RESULTS

The results showed that the input addressed to 24-month-old children with SCTs is as rich and complex as that addressed to TD peers. Moreover, no significant differences in the functions expressed by maternal input were found (all ps > 0.05). Comparing the children with weak lexical ability and the children with typical lexical ability in our sample, having a poor vocabulary at 24 months of age showed a significant influence on the maternal input features: the input addressed to children with weak lexical ability was characterised by a higher presence of attention getters (U = 217.00, p = 0.007) and a lower proportion of questions (U = 236.00, p = 0.017) than that of mothers of typically-talking children.

CONCLUSIONS AND IMPLICATIONS

At 24 months of age, it seems that the presence of a language delay and not belonging to the clinical group of children with SCTs influences the functional characteristics of the maternal input. It is important to support the parents of children with SCTs during the communication process and later during their child's development, leading them to observe their children's manifested skills rather than looking for possible predicted difficulties.

WHAT THIS PAPER ADDS

What is already known on the subject Studies in the literature demonstrated how mothers can generally adapt their input to their child's characteristics. To our knowledge, only two recent studies analysed the maternal input addressed to children with SCT at 8 months of age, highlighting significant differences. What this paper adds to existing knowledge The maternal input addressed to children with SCT at 24 months of age is not different from that addressed to TD children. At 24 months of age, the mothers adapt their input to the verbal competence shown by their child (weak lexical ability versus typically-talking), while belonging to the clinical group does not show an influence. What are the potential or actual clinical implications of this work? All the participants of the present study received prenatal diagnosis disclosure by an expert team of professionals, and they were all involved in a longitudinal study aimed at monitoring the children's development and supporting their parents. These results show that giving clear and complete information about possible development paths to parents of children with SCTs during diagnosis disclosure is crucial. Moreover, supporting the parents during the communication process and later during their child's development is fundamental, leading them to observe their children's manifested skills rather than looking for possible predicted difficulties.

Acoustic characteristics of infant- and foreigner-directed speech with Mandarin as the target language

The quality of speech input influences the efficiency of L1 and L2 acquisition. This study examined modifications in infant-directed speech (IDS) and foreigner-directed speech (FDS) in Standard Mandarin-a tonal language-and explored how IDS and FDS features were manifested in disyllabic words and a longer discourse. The study aimed to determine which characteristics of IDS and FDS were enhanced in comparison with adult-directed speech (ADS), and how IDS and FDS differed when measured in a common set of acoustic parameters. For words, it was found that tone-bearing vowel duration, mean and range of fundamental frequency (F0), and the lexical tone contours were enhanced in IDS and FDS relative to ADS, except for the dipping Tone 3 that exhibited an unexpected lowering in FDS, but no modification in IDS when compared with ADS. For the discourse, different aspects of temporal and F0 enhancements were emphasized in IDS and FDS: the mean F0 was higher in IDS whereas the total discourse duration was greater in FDS. These findings add to the growing literature on L1 and L2 speech input characteristics and their role in language acquisition.

Predicting Social Competence in Autistic and Non-Autistic Children: Effects of Prosody and the Amount of Speech Input

PURPOSE

Autistic individuals often face challenges perceiving and expressing emotions, potentially stemming from differences in speech prosody. Here we explore how autism diagnoses between groups, and measures of social competence within groups may be related to, first, children's speech characteristics (both prosodic features and amount of spontaneous speech), and second, to these two factors in mothers' speech to their children.

METHODS

Autistic (n = 21) and non-autistic (n = 18) children, aged 7-12 years, participated in a Lego-building task with their mothers, while conversational speech was recorded. Mean F0, pitch range, pitch variability, and amount of spontaneous speech were calculated for each child and their mother.

RESULTS

The results indicated no differences in speech characteristics across autistic and non-autistic children, or across their mothers, suggesting that conversational context may have large effects on whether differences between autistic and non-autistic populations are found. However, variability in social competence within the group of non-autistic children (but not within autistic children) was predictive of children's mean F0, pitch range and pitch variability. The amount of spontaneous speech produced by mothers (but not their prosody) predicted their autistic children's social competence, which may suggest a heightened impact of scaffolding for mothers of autistic children.

CONCLUSION

Together, results suggest complex interactions between context, social competence, and adaptive parenting strategies in driving prosodic differences in children's speech.

Effects of parents' voice on reducing heel puncture pain in high-risk newborns: A randomized controlled trial

BACKGROUND

High-risk newborns, such as premature or severely ill infants, often experience painful treatments and separation from their parents. While previous studies have focused on the positive impacts of a mother's voice on newborns' physiology and pain response, research on the father's voice and vocal acoustics in high-risk newborns is limited.

AIM

To examine whether parents' voices reduce heel puncture pain in high-risk newborns and the relationship between parents' vocal acoustics, physiological parameters and pain response.

STUDY DESIGN

A randomized controlled clinical trial was conducted with 105 high-risk newborn-parent dyads. Participants were randomly assigned to three groups: recorded mother's voice, recorded father's voice or control group without any recorded voice. Outcome measures included heart rate, respiratory rate, oxygen saturation and pain response assessed using the Neonatal Infant Pain Scale. Data analysis utilized generalized estimation equations, and parents' vocal acoustics were analysed using Praat voice credit software.

RESULTS

The mother's voice group exhibited significantly lower heart rates at 1, 5 and 10 min after the procedure, along with lower respiratory rates and pain levels at 5 and 10 min after the procedure compared with the control group. Similarly, the father's voice group demonstrated significantly lower heart rates at 1 and 5 min after the procedure, decreased respiratory rates at 5 and 10 min after the procedure and reduced pain levels at 1 and 5 to 10 min after the procedure compared with the control group. Higher minimum and mean pitches in parents' voices correlated with slower heart rates, while slower parental speech was associated with reduced newborn pain.

CONCLUSION

Both maternal and paternal vocal interventions alleviated pain during heel puncture procedures among high-risk newborns.

RELEVANCE TO CLINICAL PRACTICE

The noninvasive intervention serves as a reference for parental participation in care. Nurses can help parents to intervene with the acoustic characteristics that alleviate pain among high-risk newborns.

Attention-sensitive signalling by 7- to 20-month-old infants in a comparative perspective

Attention-sensitive signalling is the pragmatic skill of signallers who adjust the modality of their communicative signals to their recipient's attention state. This study provides the first comprehensive evidence for its onset and development in 7-to 20-month-olds human infants, and underlines its significance for language acquisition and evolutionary history. Mother-infant dyads (N = 30) were studied in naturalistic settings, sampled according to three developmental periods (in months); [7-10], [11-14], and [15-20]. Infant's signals were classified by dominant perceptible sensory modality and proportions compared according to their mother's visual attention, infant-directed speech and tactile contact. Maternal visual attention and infant-directed speech were influential on the onset and steepness of infants' communicative adjustments. The ability to inhibit silent-visual signals towards visually inattentive mothers (unimodal adjustment) predated the ability to deploy audible-or-contact signals in this case (cross-modal adjustment). Maternal scaffolding of infant's early pragmatic skills through her infant-directed speech operates on the facilitation of infant's unimodal adjustment, the preference for oral over gestural signals, and the audio-visual combinations of signals. Additionally, breakdowns in maternal visual attention are associated with increased use of the audible-oral modality/channel. The evolutionary role of the sharing of attentional resources between parents and infants into the emergence of modern language is discussed.

Theta power relates to infant object encoding in naturalistic mother-infant interactions

This study investigates infants' neural and behavioral responses to maternal ostensive signals during naturalistic mother-infant interactions and their effects on object encoding. Mothers familiarized their 9- to 10-month-olds (N = 35, 17 females, mainly White, data collection: 2018-2019) with objects with or without mutual gaze, infant-directed speech, and calling the infant's name. Ostensive signals focused infants' attention on objects and their mothers. Infant theta activity synchronized and alpha activity desynchronized during interactions compared to a nonsocial resting phase (Cohen' d: 0.49-0.75). Yet, their amplitudes were unrelated to maternal ostensive signals. Ostensive signals did not facilitate object encoding. However, higher infant theta power during encoding predicted better subsequent object recognition. Results strengthen the role of theta-band power for early learning processes.

The role of acoustic features of maternal infant-directed singing in enhancing infant sensorimotor, language and socioemotional development

The quality of infant-directed speech (IDS) and infant-directed singing (IDSi) are considered vital to children, but empirical studies on protomusical qualities of the IDSi influencing infant development are rare. The current prospective study examines the role of IDSi acoustic features, such as pitch variability, shape and movement, and vocal amplitude vibration, timbre, and resonance, in associating with infant sensorimotor, language, and socioemotional development at six and 18 months. The sample consists of 236 Palestinian mothers from Gaza Strip singing to their six-month-olds a song by their own choice. Maternal IDSi was recorded and analyzed by the OpenSMILE- tool to depict main acoustic features of pitch frequencies, variations, and contours, vocal intensity, resonance formants, and power. The results are based on completed 219 maternal IDSi. Mothers reported about their infants' sensorimotor, language-vocalization, and socioemotional skills at six months, and psychologists tested these skills by Bayley Scales for Infant Development at 18 months. Results show that maternal IDSi characterized by wide pitch variability and rich and high vocal amplitude and vibration were associated with infants' optimal sensorimotor, language vocalization, and socioemotional skills at six months, and rich and high vocal amplitude and vibration predicted these optimal developmental skills also at 18 months. High resonance and rhythmicity formants were associated with optimal language and vocalization skills at six months. To conclude, the IDSi is considered important in enhancing newborn and risk infants' wellbeing, and the current findings argue that favorable acoustic singing qualities are crucial for optimal multidomain development across infancy.

Infant-Directed Speech to Preterm Infants during the First Year Postpartum: The Influence of Preterm Birth Weight and Maternal Parenting Stress

Premature birth can increase the level of parenting stress (PS), especially in the case of parents of high-risk infants (extremely low birth weight (ELBW) and very low birth weight (VLBW)). Though published research has explored how maternal PS influences early dyadic interactions, limited research has focused on infant-directed speech (IDS), and no studies have investigated the link between prematurity severity based on birth weight and maternal IDS. This study, involving 100 mother-infant dyads, categorized into 30 ELBW premature infants, 30 VLBW premature infants, and 40 full-term (FT) ones, examined the impact of preterm birth weight and maternal parenting stress on IDS features during early interactions at 3 and 9 months postpartum. Maternal input was assessed using the CHILDES system, while parenting stress was evaluated using the Parenting Stress Index-Short Form. The results revealed that high-risk conditions (ELBW preterm birth and high parenting stress) at 3 months were associated with reduced affect-salient speech and increased questioning. IDS functional patterns, specifically the proportion of affect-salient speech and questions, were influenced by both birth weight groups and parenting stress levels at 3 months but not at 9 months. These findings highlight the need to assess, within the context of prematurity, both birth weight and parenting stress in clinical practice, offering insights for developing interventions supporting positive parent-infant interactions and facilitating infant development.

Relating the prosody of infant-directed speech to children's vocabulary size

This study examines correlations between the prosody of infant-directed speech (IDS) and children's vocabulary size. We collected longitudinal speech data and vocabulary information from Dutch mother-child dyads with children aged 18 (N = 49) and 24 (N = 27) months old. We took speech context into consideration and distinguished between prosody when mothers introduce familiar vs. unfamiliar words to their children. The results show that IDS mean pitch predicts children's vocabulary growth between 18 and 24 months. In addition, the degree of prosodic modification when mothers introduce unfamiliar words to their children correlates with children's vocabulary growth during this period. These findings suggest that the prosody of IDS, especially in word-learning contexts, may serve linguistic purposes.

Infant-directed speech facilitates word learning through attentional mechanisms: An fNIRS study of toddlers

The speech register that adults especially caregivers use when interacting with infants and toddlers, that is, infant-directed speech (IDS) or baby talk, has been reported to facilitate language development throughout the early years. However, the neural mechanisms as well as why IDS results in such a developmental faciliatory effect remain to be investigated. The current study uses functional near-infrared spectroscopy (fNIRS) to evaluate two alternative hypotheses of such a facilitative effect, that IDS serves to enhance linguistic contrastiveness or to attract the child's attention. Behavioral and fNIRS data were acquired from twenty-seven Cantonese-learning toddlers 15-20 months of age when their parents spoke to them in either an IDS or adult-directed speech (ADS) register in a naturalistic task in which the child learned four disyllabic pseudowords. fNIRS results showed significantly greater neural responses to IDS than ADS register in the left dorsolateral prefrontal cortex (L-dlPFC), but opposite response patterns in the bilateral inferior frontal gyrus (IFG). The differences in fNIRS responses to IDS and to ADS in the L-dlPFC and the left parietal cortex (L-PC) showed significantly positive correlations with the differences in the behavioral word-learning performance of toddlers. The same fNIRS measures in the L-dlPFC and right PC (R-PC) of toddlers were significantly correlated with pitch range differences of parents between the two speech conditions. Together, our results suggest that the dynamic prosody in IDS increased toddlers' attention through greater involvement of the left frontoparietal network that facilitated word learning, compared to ADS. RESEARCH HIGHLIGHTS: This study for the first time examined the neural mechanisms of how infant-directed speech (IDS) facilitates word learning in toddlers. Using fNIRS, we identified the cortical regions that were directly involved in IDS processing. Our results suggest that IDS facilitates word learning by engaging a right-lateralized prosody processing and top-down attentional mechanisms in the left frontoparietal networks. The language network including the inferior frontal gyrus and temporal cortex was not directly involved in IDS processing to support word learning.

Does Electrophysiological Maturation Shape Language Acquisition?

Infants master temporal patterns of their native language at a developmental trajectory from slow to fast: Shortly after birth, they recognize the slow acoustic modulations specific to their native language before tuning into faster language-specific patterns between 6 and 12 months of age. We propose here that this trajectory is constrained by neuronal maturation-in particular, the gradual emergence of high-frequency neural oscillations in the infant electroencephalogram. Infants' initial focus on slow prosodic modulations is consistent with the prenatal availability of slow electrophysiological activity (i.e., theta- and delta-band oscillations). Our proposal is consistent with the temporal patterns of infant-directed speech, which initially amplifies slow modulations, approaching the faster modulation range of adult-directed speech only as infants' language has advanced sufficiently. Moreover, our proposal agrees with evidence from premature infants showing maturational age is a stronger predictor of language development than ex utero exposure to speech, indicating that premature infants cannot exploit their earlier availability of speech because of electrophysiological constraints. In sum, we provide a new perspective on language acquisition emphasizing neuronal development as a critical driving force of infants' language development.

Infant-directed speech does not always involve exaggerated vowel distinctions: Evidence from Danish

This study compared the acoustic properties of 26 (100% female, 100% monolingual) Danish caregivers' spontaneous speech addressed to their 11- to 24-month-old infants (infant-directed speech, IDS) and an adult experimenter (adult-directed speech, ADS). The data were collected between 2016 and 2018 in Aarhus, Denmark. Prosodic properties of Danish IDS conformed to cross-linguistic patterns, with a higher pitch, greater pitch variability, and slower articulation rate than ADS. However, an acoustic analysis of vocalic properties revealed that Danish IDS had a reduced or similar vowel space, higher within-vowel variability, raised formants, and lower degree of vowel discriminability compared to ADS. None of the measures, except articulation rate, showed age-related differences. These results push for future research to conduct theory-driven comparisons across languages with distinct phonological systems.

Mothers' and fathers' infant-directed speech have similar acoustic properties, but these are not associated with direct or indirect measures of word comprehension in 8-month-old infants

Previous research on infant-directed speech (IDS) and its role in infants' language development has largely focused on mothers, with fathers being investigated scarcely. Here we examine the acoustics of IDS as compared to adult-directed speech (ADS) in Norwegian mothers and fathers to 8-month-old infants, and whether these relate to direct (eye-tracking) and indirect (parental report) measures of infants' word comprehension. Forty-five parent-infant dyads participated in the study. Parents (24 mothers, 21 fathers) were recorded reading a picture book to their infant (IDS), and to an experimenter (ADS), ensuring identical linguistic context across speakers and registers. Results showed that both mothers' and fathers' IDS had exaggerated prosody, expanded vowel spaces, as well as more variable and less distinct vowels. We found no evidence that acoustic features of parents' speech were associated with infants' word comprehension. Potential reasons for the lack of such a relationship are discussed.

Parents tune their vowels to the emergence of children's words

The aim of this study was to investigate the acoustic vowel space area in infant directed speech (IDS). The research question is whether the vowel space is expanded or remains constant in IDS. A corpus of spontaneous interactions of 9 dyads followed monthly from the age of 6 to 24 months was analyzed. The occurrences in the parents' speech of each word that the children eventually acquired were extracted. The surface of the vowel triangle and the convex hull of all vowels were computed. The main result is that the development of the vowel space in IDS follows an inverted U-shaped curve: the vowel space starts relatively small, gradually increases as the child's first word use approaches, and decreases again afterwards. These findings show that parents adapt their articulation to the evolving linguistic abilities of their child, and this adaptation can be detected at the level of individual lexical items.

Music and language in the crib: Early cross-domain effects of experience on categorical perception of prominence in spoken language

Rhythm perception helps young infants find structure in both speech and music. However, it remains unknown whether categorical perception of suprasegmental linguistic rhythm signaled by a co-variation of multiple acoustic cues can be modulated by prior between- (music) and within-domain (language) experience. Here we tested 6-month-old German-learning infants' ability to have a categorical perception of lexical stress, a linguistic prominence signaled through the co-variation of pitch, intensity, and duration. By measuring infants' pupil size, we find that infants as a group fail to perceive co-variation of these acoustic cues as categorical. However, at an individual level, infants with above-average exposure to music and language at home succeeded. Our results suggest that early exposure to music and infant-directed language can boost the categorical perception of prominence. RESEARCH HIGHLIGHTS: 6-month-old German-learning infants' ability to perceive lexical stress prominence categorically depends on exposure to music and language at home. Infants with high exposure to music show categorical perception. Infants with high exposure to infant-directed language show categorical perception. Co-influence of high exposure to music and infant-directed language may be especially beneficial for categorical perception. Early exposure to predictable rhythms boosts categorical perception of prominence.

The relationship between pitch contours in infant-directed speech and early signs of autism in infancy

PURPOSE

Mother-infant interactions during the first year of life are crucial to healthy infant development. The infant-directed speech (IDS), and specifically pitch contours, used by mothers during interactions are associated with infant language and social development. However, little research has examined pitch contours towards infants with socio-communication and language differences, such as those displaying early signs of autism spectrum disorder (autism). This study aimed to explore the association of infant autism signs and pitch contours used by mothers with their 12-month-old infants.

METHOD

Mother-infant dyads (n = 109) were recruited from the University of Newcastle BabyLab. Parent-infant dyads completed a 15-min interaction, from which a total of 36,128 pitch contours were measured and correlated with infant autism signs. Infant autism signs were assessed via parent-report (First Year Inventory; Reznick et al., 2007). A subset of high-risk infants (admitted to a neonatal intensive care unit, n = 29) also received an observation-based assessment (Autism Detection in Early Childhood; Young & Nah, 2016).

RESULTS

Mothers used fewer sinusoidal contours when they rated their infant as displaying more autism signs (rs = - .30, p = .004) and more autism-related sensory regulation issues (rs = - .31, p = .001). Mothers used fewer flat contours if their infant displayed more researcher-rated autism signs (r2 = - .39, p = .04).

CONCLUSIONS

This study provides the early evidence that maternal pitch contours in IDS are related to early autism signs in infancy. If our findings are replicated in follow up studies where infants are followed to diagnosis, maternal IDS may be an important element of future early intervention protocols that focus on communication for infants with risk for autism.

Maturation of auditory cortex neural responses during infancy and toddlerhood

The infant auditory system rapidly matures across the first years of life, with a primary goal of obtaining ever-more-accurate real-time representations of the external world. Our understanding of how left and right auditory cortex neural processes develop during infancy, however, is meager, with few studies having the statistical power to detect potential hemisphere and sex differences in primary/secondary auditory cortex maturation. Using infant magnetoencephalography (MEG) and a cross-sectional study design, left and right auditory cortex P2m responses to pure tones were examined in 114 typically developing infants and toddlers (66 males, 2 to 24 months). Non-linear maturation of P2m latency was observed, with P2m latencies decreasing rapidly as a function of age during the first year of life, followed by slower changes between 12 and 24 months. Whereas in younger infants auditory tones were encoded more slowly in the left than right hemisphere, similar left and right P2m latencies were observed by ∼21 months of age due to faster maturation rate in the left than right hemisphere. No sex differences in the maturation of the P2m responses were observed. Finally, an earlier left than right hemisphere P2m latency predicted better language performance in older infants (12 to 24 months). Findings indicate the need to consider hemisphere when examining the maturation of auditory cortex neural activity in infants and toddlers and show that the pattern of left-right hemisphere P2m maturation is associated with language performance.

Infant-Directed Speech to 3-Month-Old Severe Preterm Infants: The Influence of Birth Weight and Maternal Depressive Symptoms

Severe premature birth (<32 weeks) is a risk factor for the development of maternal perinatal depression, while also affecting dyadic interactions and child outcomes. Although several studies have examined the impacts of prematurity and depression on early interactions, only a few studies have investigated the features of maternal verbal input. Furthermore, no study has investigated the relationship between the effect of severity of prematurity according to birth weight and maternal input. This study aimed to explore the effects of the severity of preterm birth and postnatal depression on maternal input during early interactions. The study included 64 mother-infant dyads, classified into three groups: 17 extremely low birth weight (ELBW) preterm infants, 17 very low birth weight (VLBW) preterm infants, and 30 full-term (FT) infants. At 3 months postpartum (corrected age for preterm infants), the dyads participated in a 5-min free interaction session. Maternal input was analyzed using the CHILDES system in terms of lexical and syntactic complexity (i.e., word types, word tokens, mean length of the utterance) and functional features. Maternal postnatal depression (MPD) was assessed using the Edinburgh Postnatal Depression Scale. The results showed that in high-risk conditions (i.e., ELBW preterm birth and maternal postnatal depression), maternal input was characterized by a lower frequency of affect-salient speech and a higher proportion of information-salient speech, specifically as directives and questions, suggesting that mothers in these conditions may experience more difficulty in conveying affective content to their infants. Moreover, the more frequent use of questions may reflect an interactive style characterized by a higher level of intrusiveness. These findings provide preliminary evidence of the impacts of prematurity severity and maternal depression on maternal verbal input, highlighting the importance of assessing both factors in clinical practice. Understanding the mechanisms underlying the impacts of prematurity and depression on early interactions may inform the development of tailored interventions aimed at promoting positive parent-infant interactions and child development.

Maternal and paternal depressive symptoms and parental vocalisation behaviours in infancy: findings from UK-based birth cohort

Background

Both maternal and paternal postnatal depression (PND) are associated with increased risk of less optimal offspring developmental outcomes. Early exposure to differences in maternal and paternal vocalisation behaviours associated with maternal and paternal PND may be important in this relationship. However, little research has captured vocalisation patterns at home without researchers present.

Objectives

This study sought to examine the associations between maternal and paternal PND and various aspects of parental vocalisation behaviours.

Methods

Mothers (n = 104) and fathers (n = 34) of six-months old infants from the Avon Longitudinal Study of Parents and Children Generation-2 (ALSPAC-G2) provided video footage of mother- and father-infant interactions filmed at home using the head-worn video cameras (headcams) without the need for researchers to be present. Twenty-five mother-infant and father-infant interactions were coded on multiple aspects of parental and infant vocalisation behaviours using the micro-behavioural observational coding system. Parental (PND) was measured using the Edinburgh Postnatal Depression Scale (EPDS; total score).

Results

Frequencies and duration of vocalisation behaviours were similar in mothers and fathers. However, there was an indication that fathers demonstrated higher frequency and duration of commands, exclamations and ironic/sarcastic tone, and criticisms compared to mothers, while mothers engaged in more teaching compared to fathers. Linear regression models indicated that maternal and paternal PND were not associated with the majority of vocalisation behaviours. However, there were some specific patterns observed, mostly related to the emotional tone of the vocalisations. Higher levels of maternal PND were associated with lower frequency of speech in a neutral tone, frequency and duration of use of humour, and increased duration of speech in a positive tone. Higher levels of paternal PND were associated with higher mean duration of speech, infant-directed speech, higher frequency and duration of laughing, and increased duration of speech using questions and encouragement.

Conclusion

These findings extend existing research by investigating the associations between maternal and paternal PND and a wide range of vocalisation behaviours captured and coded using innovative methods and in a more ecologically valid way than previous studies.

Six facial prosodic expressions caregivers similarly display to infants and dogs

Parents tend to use a specific communication style, including specific facial expressions, when speaking to their preverbal infants which has important implications for children's healthy development. In the present study, we investigated these facial prosodic features of caregivers with a novel method that compares infant-, dog- and adult-directed communication. We identified three novel facial displays in addition to the already described three facial expressions (i.e. the 'prosodic faces') that mothers and fathers are typically displaying when interacting with their 1-18 month-old infants and family dogs, but not when interacting with another adult. The so-called Special Happy expression proved to be the most frequent face type during infant- and dog-directed communication which always includes a Duchenne marker to convey an honest and intense happy emotion of the speaker. These results suggest that the 'prosodic faces' play an important role in both adult-infant and human-dog interactions and fulfil specific functions: to call and maintain the partner's attention, to foster emotionally positive interactions, and to strengthen social bonds. Our study highlights the relevance of future comparative studies on facial prosody and its potential contribution to healthy emotional and cognitive development of infants.

Association of Postpartum Maternal Mood With Infant Speech Perception at 2 and 6.5 Months of Age

IMPORTANCE

Language development builds on speech perception, with early disruptions increasing the risk for later language difficulties. Although a major postpartum depressive episode is associated with language development, this association has not been investigated among infants of mothers experiencing a depressed mood at subclinical levels after birth, even though such a mood is frequently present in the first weeks after birth. Understanding whether subclinical depressed maternal mood after birth is associated with early language development is important given opportunities of coping strategies for subclinical depressed mood.

OBJECTIVE

To examine whether depressed maternal mood at subclinical levels 2 months after birth is associated with infant speech perception trajectories from ages 2 to 6.5 months.

DESIGN, SETTING, AND PARTICIPANTS

In this longitudinal cohort study conducted between January 1, 2018, and October 31, 2019, 46 healthy, monolingual German mother-infant dyads were tested. The sample was recruited from the infants database of the Max Planck Institute for Human Cognitive and Brain Sciences. Initial statistical analysis was performed between January 1 and March 31, 2021; the moderation analysis (results reported herein) was conducted between July 1 and July 31, 2022.

EXPOSURES

Mothers reported postpartum mood via the German version of the Edinburgh Postnatal Depression Scale (higher scores indicated higher levels of depressed mood, with a cutoff of 13 points indicating a high probability of clinical depression) when their infants were 2 months old.

MAIN OUTCOMES AND MEASURES

Electrophysiological correlates of infant speech perception (mismatch response to speech stimuli) were tested when the infants were aged 2 months (initial assessment) and 6.5 months (follow-up).

RESULTS

A total of 46 mothers (mean [SD] age, 32.1 [3.8] years) and their 2-month-old children (mean [SD] age, 9.6 [1.2] weeks; 23 girls and 23 boys) participated at the initial assessment, and 36 mothers (mean [SD] age, 32.2 [4.1] years) and their then 6.5-month-old children (mean [SD] age, 28.4 [1.5 weeks; 18 girls and 18 boys) participated at follow-up. Moderation analyses revealed that more depressed maternal subclinical postpartum mood (mean [SD] Edinburgh Postnatal Depression Scale score, 4.8 [3.6]) was associated with weaker longitudinal changes of infants' electrophysiological brain responses to syllable pitch speech information from ages 2 to 6.5 months (coefficient: 0.68; 95% CI, 0.03-1.33; P = .04).

CONCLUSIONS AND RELEVANCE

The results of this cohort study suggest that infant speech perception trajectories are correlated with subclinical depressed mood in postpartum mothers. This finding lays the groundwork for future research on early support for caregivers experiencing depressed mood to have a positive association with children's language development.

The Acoustic Features and Didactic Function of Foreigner-Directed Speech: A Scoping Review

PURPOSE

This scoping review considers the acoustic features of a clear speech register directed to nonnative listeners known as foreigner-directed speech (FDS). We identify vowel hyperarticulation and low speech rate as the most representative acoustic features of FDS; other features, including wide pitch range and high intensity, are still under debate. We also discuss factors that may influence the outcomes and characteristics of FDS. We start by examining accommodation theories, outlining the reasons why FDS is likely to serve a didactic function by helping listeners acquire a second language (L2). We examine how this speech register adapts to listeners' identities and linguistic needs, suggesting that FDS also takes listeners' L2 proficiency into account. To confirm the didactic function of FDS, we compare it to other clear speech registers, specifically infant-directed speech and Lombard speech.

CONCLUSIONS

Our review reveals that research has not yet established whether FDS succeeds as a didactic tool that supports L2 acquisition. Moreover, a complex set of factors determines specific realizations of FDS, which need further exploration. We conclude by summarizing open questions and indicating directions and recommendations for future research.

Rhythm May Be Key to Linking Language and Cognition in Young Infants: Evidence From Machine Learning

Rhythm is key to language acquisition. Across languages, rhythmic features highlight fundamental linguistic elements of the sound stream and structural relations among them. A sensitivity to rhythmic features, which begins in utero, is evident at birth. What is less clear is whether rhythm supports infants' earliest links between language and cognition. Prior evidence has documented that for infants as young as 3 and 4 months, listening to their native language (English) supports the core cognitive capacity of object categorization. This precocious link is initially part of a broader template: listening to a non-native language from the same rhythmic class as (e.g., German, but not Cantonese) and to vocalizations of non-human primates (e.g., lemur, Eulemur macaco flavifrons, but not birds e.g., zebra-finches, Taeniopygia guttata) provide English-acquiring infants the same cognitive advantage as does listening to their native language. Here, we implement a machine-learning (ML) approach to ask whether there are acoustic properties, available on the surface of these vocalizations, that permit infants' to identify which vocalizations are candidate links to cognition. We provided the model with a robust sample of vocalizations that, from the vantage point of English-acquiring 4-month-olds, either support object categorization (English, German, lemur vocalizations) or fail to do so (Cantonese, zebra-finch vocalizations). We assess (a) whether supervised ML classification models can distinguish those vocalizations that support cognition from those that do not, and (b) which class(es) of acoustic features (including rhythmic, spectral envelope, and pitch features) best support that classification. Our analysis reveals that principal components derived from rhythm-relevant acoustic features were among the most robust in supporting the classification. Classifications performed using temporal envelope components were also robust. These new findings provide in principle evidence that infants' earliest links between vocalizations and cognition may be subserved by their perceptual sensitivity to rhythmic and spectral elements available on the surface of these vocalizations, and that these may guide infants' identification of candidate links to cognition.

Infant-Directed Speech From a Multidimensional Perspective: The Interplay of Infant Birth Status, Maternal Parenting Stress, and Dyadic Co-regulation on Infant-Directed Speech Linguistic and Pragmatic Features

Infant-directed speech (IDS), the particular form of spontaneous language observed in interactions between parents and their infants, is a crucial aspect of the mother-infant interaction and an index of the attunement of maternal linguistic input to her infant communicative abilities and needs during dyadic interactions. The present study aimed to explore linguistic and pragmatic features of IDS during mother-infant interactions at 3-month of infant age. The effects of infant (birth status: preterm vs. full-term birth), maternal (perceived parenting stress) and dyadic (dyadic co-regulation) factors on IDS were explored. Results evidenced few differences between the groups on IDS linguistic characteristics. Moreover, observing the interaction of birth status and dyadic co-regulation, full-term mothers varied their IDS pragmatic features according to the quality of co-regulation while preterm mothers did not. Parenting stress was associated to specific linguistic IDS features independently from the birth status. Findings are discussed underling implications for the study of preterm dyads interactions and the importance to consider the interplay of several factors in affecting the quality of IDS.

Singing to infants matters: Early singing interactions affect musical preferences and facilitate vocabulary building

This research revealed that the frequency of reported parent-infant singing interactions predicted 6-month-old infants' performance in laboratory music experiments and mediated their language development in the second year. At 6 months, infants (n = 36) were tested using a preferential listening procedure assessing their sustained attention to instrumental and sung versions of the same novel tunes whilst the parents completed an ad-hoc questionnaire assessing home musical interactions with their infants. Language development was assessed with a follow-up when the infants were 14-month-old (n = 26). The main results showed that 6-month-olds preferred listening to sung rather than instrumental melodies, and that self-reported high levels of parental singing with their infants [i] were associated with less pronounced preference for the sung over the instrumental version of the tunes at 6 months, and [ii] predicted significant advantages on the language outcomes in the second year. The results are interpreted in relation to conceptions of developmental plasticity.

The function and evolution of child-directed communication

Humans communicate with small children in unusual and highly conspicuous ways (child-directed communication (CDC)), which enhance social bonding and facilitate language acquisition. CDC-like inputs are also reported for some vocally learning animals, suggesting similar functions in facilitating communicative competence. However, adult great apes, our closest living relatives, rarely signal to their infants, implicating communication surrounding the infant as the main input for infant great apes and early humans. Given cross-cultural variation in the amount and structure of CDC, we suggest that child-surrounding communication (CSC) provides essential compensatory input when CDC is less prevalent-a paramount topic for future studies.

Natural Infant-Directed Speech Facilitates Neural Tracking of Prosody

Infants prefer to be addressed with infant-directed speech (IDS). IDS benefits language acquisition through amplified low-frequency amplitude modulations. It has been reported that this amplification increases electrophysiological tracking of IDS compared to adult-directed speech (ADS). It is still unknown which particular frequency band triggers this effect. Here, we compare tracking at the rates of syllables and prosodic stress, which are both critical to word segmentation and recognition. In mother-infant dyads (n=30), mothers described novel objects to their 9-month-olds while infants' EEG was recorded. For IDS, mothers were instructed to speak to their children as they typically do, while for ADS, mothers described the objects as if speaking with an adult. Phonetic analyses confirmed that pitch features were more prototypically infant-directed in the IDS-condition compared to the ADS-condition. Neural tracking of speech was assessed by speech-brain coherence, which measures the synchronization between speech envelope and EEG. Results revealed significant speech-brain coherence at both syllabic and prosodic stress rates, indicating that infants track speech in IDS and ADS at both rates. We found significantly higher speech-brain coherence for IDS compared to ADS in the prosodic stress rate but not the syllabic rate. This indicates that the IDS benefit arises primarily from enhanced prosodic stress. Thus, neural tracking is sensitive to parents' speech adaptations during natural interactions, possibly facilitating higher-level inferential processes such as word segmentation from continuous speech.

Vocal communication across cultures: theoretical and methodological issues

The study of human vocal communication has been conducted primarily in Western, educated, industrialized, rich, democratic (WEIRD) societies. Recently, cross-cultural investigations in several domains of voice research have been expanding into more diverse populations. Theoretically, it is important to understand how universals and cultural variations interact in vocal production and perception, but cross-cultural voice research presents many methodological challenges. Experimental methods typically used in WEIRD societies are often not possible to implement in many populations such as rural, small-scale societies. Moreover, theoretical and methodological issues are often unnecessarily intertwined. Here, I focus on three areas of cross-cultural voice modulation research: (i) vocal signalling of formidability and dominance, (ii) vocal emotions, and (iii) production and perception of infant-directed speech. Research in these specific areas illustrates challenges that apply more generally across the human behavioural sciences but also reveals promise as we develop our understanding of the evolution of human communication. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part II)'.

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

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

Associations between acoustic features of maternal speech and infants' emotion regulation following a social stressor

Caregiver voices may provide cues to mobilize or calm infants. This study examined whether maternal prosody predicted changes in infants' biobehavioral state after the still face, a stressor in which the mother withdraws and reinstates social engagement. Ninety-four dyads participated in the study (infant age 4-8 months). Infants' heart rate and respiratory sinus arrhythmia (measuring cardiac vagal tone) were derived from an electrocardiogram (ECG). Infants' behavioral distress was measured by negative vocalizations, facial expressions, and gaze aversion. Mothers' vocalizations were measured via a composite of spectral analysis and spectro-temporal modulation using a two-dimensional fast Fourier transformation of the audio spectrogram. High values on the maternal prosody composite were associated with decreases in infants' heart rate (β = -.26, 95% CI: [-0.46, -0.05]) and behavioral distress (β = -.23, 95% CI: [-0.42, -0.03]), and increases in cardiac vagal tone in infants whose vagal tone was low during the stressor (1 SD below mean β = .39, 95% CI: [0.06, 0.73]). High infant heart rate predicted increases in the maternal prosody composite (β = .18, 95% CI: [0.03, 0.33]). These results suggest specific vocal acoustic features of speech that are relevant for regulating infants' biobehavioral state and demonstrate mother-infant bi-directional dynamics.

Relationship Between Parent Vowel Hyperarticulation in Infant-Directed Speech and Infant Phonetic Complexity on the Level of Conversational Turns

When speaking to infants, parents typically use infant-directed speech, a speech register that in several aspects differs from that directed to adults. Vowel hyperarticulation, that is, extreme articulation of vowels, is one characteristic sometimes found in infant-directed speech, and it has been suggested that there exists a relationship between how much vowel hyperarticulation parents use when speaking to their infant and infant language development. In this study, the relationship between parent vowel hyperarticulation and phonetic complexity of infant vocalizations is investigated. Previous research has shown that on the level of subject means, a positive correlational relationship exists. However, the previous findings do not provide information about the directionality of that relationship. In this study the relationship is investigated on a conversational turn level, which makes it possible to draw conclusions on whether the behavior of the infant is impacting the parent, the behavior of the parent is impacting the infant, or both. Parent vowel hyperarticulation was quantified using the vhh-index, a measure that allows vowel hyperarticulation to be estimated for individual vowel tokens. Phonetic complexity of infant vocalizations was calculated using the Word Complexity Measure for Swedish. Findings were unexpected in that a negative relationship was found between parent vowel hyperarticulation and phonetic complexity of the immediately following infant vocalization. Directionality was suggested by the fact that no such relationship was found between infant phonetic complexity and vowel hyperarticulation of the immediately following parent utterance. A potential explanation for these results is that high degrees of vowel hyperarticulation either provide, or co-occur with, large amounts of phonetic and/or linguistic information, which may occupy processing resources to an extent that affects production of the next vocalization.

Newborn Incubators Do Not Protect from High Noise Levels in the Neonatal Intensive Care Unit and Are Relevant Noise Sources by Themselves

BACKGROUND

While meaningful sound exposure has been shown to be important for newborn development, an excess of noise can delay the proper development of the auditory cortex.

AIM

The aim of this study was to assess the acoustic environment of a preterm baby in an incubator on a newborn intensive care unit (NICU).

METHODS

An empty but running incubator (Giraffe Omnibed, GE Healthcare) was used to evaluate the incubator frequency response with 60 measurements. In addition, a full day and night period outside and inside the incubator at the NICU of the University Hospital Zurich was acoustically analyzed.

RESULTS

The fan construction inside the incubator generates noise in the frequency range of 1.3-1.5 kHz with a weighted sound pressure level (SPL) of 40.5 dB(A). The construction of the incubator narrows the transmitted frequency spectrum of sound entering the incubator to lower frequencies, but it does not attenuate transient noises such as alarms or opening and closing of cabinet doors substantially. Alarms, as generated by the monitors, the incubator, and additional devices, still pass to the newborn.

CONCLUSIONS

The incubator does protect only insufficiently from noise coming from the NICUThe transmitted frequency spectrum is changed, limiting the impact of NICU noise on the neonate, but also limiting the neonate's perception of voices. The incubator, in particular its fan, as well as alarms from patient monitors are major sources of noise. Further optimizations with regard to the sound exposure in the NICU, as well as studies on the role of the incubator as a source and modulator, are needed to meet the preterm infants' multi-sensory needs.

An Association Between Phonetic Complexity of Infant Vocalizations and Parent Vowel Hyperarticulation

Extreme or exaggerated articulation of vowels, or vowel hyperarticulation, is a characteristic commonly found in infant-directed speech (IDS). High degrees of vowel hyperarticulation in parent IDS has been tied to better speech sound category development and bigger vocabulary size in infants. In the present study, the relationship between vowel hyperarticulation in Swedish IDS to 12-month-old and phonetic complexity of infant vocalizations is investigated. Articulatory adaptation toward hyperarticulation is quantified as difference in vowel space area between IDS and adult-directed speech (ADS). Phonetic complexity is estimated using the Word Complexity Measure for Swedish (WCM-SE). The results show that vowels in IDS was more hyperarticulated than vowels in ADS, and that parents' articulatory adaptation in terms of hyperarticulation correlates with phonetic complexity of infant vocalizations. This can be explained either by the parents' articulatory behavior impacting the infants' vocalization behavior, the infants' social and communicative cues eliciting hyperarticulation in the parents' speech, or the two variables being impacted by a third, underlying variable such as parents' general communicative adaptiveness.

Neural coding of formant-exaggerated speech and nonspeech in children with and without autism spectrum disorders

The presence of vowel exaggeration in infant-directed speech (IDS) may adapt to the age-appropriate demands in speech and language acquisition. Previous studies have provided behavioral evidence of atypical auditory processing towards IDS in children with autism spectrum disorders (ASD), while the underlying neurophysiological mechanisms remain unknown. This event-related potential (ERP) study investigated the neural coding of formant-exaggerated speech and nonspeech in 24 4- to 11-year-old children with ASD and 24 typically-developing (TD) peers. The EEG data were recorded using an alternating block design, in which each stimulus type (exaggerated/non-exaggerated sound) was presented with equal probability. ERP waveform analysis revealed an enhanced P1 for vowel formant exaggeration in the TD group but not in the ASD group. This speech-specific atypical processing in ASD was not found for the nonspeech stimuli which showed similar P1 enhancement in both ASD and TD groups. Moreover, the time-frequency analysis indicated that children with ASD showed differences in neural synchronization in the delta-theta bands for processing acoustic formant changes embedded in nonspeech. Collectively, the results add substantiating neurophysiological evidence (i.e., a lack of neural enhancement effect of vowel exaggeration) for atypical auditory processing of IDS in children with ASD, which may exert a negative effect on phonetic encoding and language learning. LAY SUMMARY: Atypical responses to motherese might act as a potential early marker of risk for children with ASD. This study investigated the neural responses to such socially relevant stimuli in the ASD brain, and the results suggested a lack of neural enhancement responding to the motherese even in individuals without intellectual disability.

"Motherese" Prosody in Fetal-Directed Speech: An Exploratory Study Using Automatic Social Signal Processing

Introduction: Motherese, or emotional infant directed speech (IDS), is the specific form of speech used by parents to address their infants. The prosody of IDS has affective properties, expresses caregiver involvement, is a marker of caregiver-infant interaction quality. IDS prosodic characteristics can be detected with automatic analysis. We aimed to explore whether pregnant women “speak” to their unborn baby, whether they use motherese while speaking and whether anxio-depressive or obstetrical status impacts speaking to the fetus.

Participants and Methods: We conducted an observational study of pregnant women with gestational ages from 26 to 38 weeks. Women were recruited in a university hospital department of obstetrics. Thirty-five women agreed to participate in the study, and 26 audio records were exploitable. We collected obstetrical and sociodemographic data, pregnancy outcomes, anxiety and depressive status using the Covy and Raskin Scales, and life events using the Sensations During Pregnancy and Life Event Questionnaire. Each participant was left alone with an audio recorder with a recommendation to feel free to speak to her fetus as she would have done at home. The recording was stopped after 3 min. Audio recordings were analyzed by two methods: psycholinguist experts' annotation and computational objective automatic analyses.

Results: Most mothers (89%) reported speaking to their fetuses. We found a correlation between maternal first perceptions of fetal movements and the start of mother's speaking to fetus. Motherese prosody was detected with both annotation and automatic analysis with a significant correlation between the two methods. In this exploratory study, motherese use was not associated with maternal anxiodepressive or obstetrical status. However, the more future mothers were depressed, the less they spoke with their fetuses during the recording.

Conclusion: Fetal directed speech (FDS) can be detected during pregnancy, and it contains a period of prosody that shares the same characteristics of motherese that can be described as prenatal motherese or emotional fetal-directed speech (e-FDS). This means that pregnant women start using motherese much earlier than expected. FDS seems to be correlated with maternal first perceptions of fetal movements and depression scores. However, more research is needed to confirm these exploratory results.

The Effect of a Voice-Centered Psycho-Educational Program on Maternal Self-Efficacy: A Feasibility Study

This study examined the effect of a brief psycho-educational program, Time Together, on maternal self-efficacy, mother-infant bonding, and mood/anxiety for community-based mothers. This program centered on maternal voice, timing of interplay, and recognition of infant cues. A convergent parallel mixed-methods design included quantitative measures: the Karitane Parenting Confidence Scale, the Mother-Infant Bonding Scale, Edinburgh Postnatal Depression Scale and State & Trait Anxiety Inventory, and a sequential qualitative analysis to elaborate on the quantitative findings. Significant changes on the Karitane Parenting Confidence Scale were found. Qualitative analysis of the participant interviews and reflective diaries from the two weeks following the psycho-educational program confirmed that participation enhanced mothers' ability to understand their infant, to soothe their infant when distressed, to play and to establish an effective bedtime routine. This feasibility study indicated that this is a promising approach to improve early mother-infant interaction and maternal self-efficacy.