Relationship between rhythmic behavior and canonical babbling in infant vocal development

Which factors modulate spontaneous motor tempo? A systematic review of the literature

Intentionally or not, humans produce rhythmic behaviors (e.g., walking, speaking, and clapping). In 1974, Paul Fraisse defined rhythmic behavior as a periodic movement that obeys a temporal program specific to the subject and that depends less on the conditions of the action (p. 47). Among spontaneous rhythms, the spontaneous motor tempo (SMT) corresponds to the tempo at which someone produces movements in the absence of external stimuli, at the most regular, natural, and pleasant rhythm for him/her. However, intra- and inter-individual differences exist in the SMT values. Even if several factors have been suggested to influence the SMT (e.g., the age of participants), we do not yet know which factors actually modulate the value of the SMT. In this context, the objectives of the present systematic review are (1) to characterize the range of SMT values found in the literature in healthy human adults and (2) to identify all the factors modulating the SMT values in humans. Our results highlight that (1) the reference value of SMT is far from being a common value of 600 ms in healthy human adults, but a range of SMT values exists, and (2) many factors modulate the SMT values. We discuss our results in terms of intrinsic factors (in relation to personal characteristics) and extrinsic factors (in relation to environmental characteristics). Recommendations are proposed to assess the SMT in future research and in rehabilitative, educative, and sport interventions involving rhythmic behaviors.

Longitudinal changes in infants' rhythmic arm movements during rattle-shaking play with mothers

From early on, infants produce a variety of rhythmic behaviors—an ability that likely supports later social communication. However, it is unclear, how this rhythmic motor production changes with age. Here, we investigated the coupling between infants' arm movements across the first year of life in a social context of a rattle-shaking play with their mothers. Through longitudinal measurements at 4, 6, 9, and 12 months of age using wearable motion trackers placed on infants' arms, we show that infants (N = 40) are similarly motivated to attempt rattle-shaking across the first year of life. However, with age, they make more rattling movements with an increased frequency. Their left and right arm movements become more coupled during rattle-shaking, as shown by an increase in wavelet coherence. Infants produced more rattling movements when they were rattling alone than when their mothers were rattling or singing simultaneously. There were no differences between infants' individual and social rattling in between-arms coherence. Our results may help to understand rhythmic arm movements as precursors of motor social coordination.

Origins Of Vocal-Entangled Gesture

Gestures during speaking are typically understood in a representational framework: they represent absent or distal states of affairs by means of pointing, resemblance, or symbolic replacement. However, humans also gesture along with the rhythm of speaking, which is amenable to a non-representational perspective. Such a perspective centers on the phenomenon of vocal-entangled gestures and builds on evidence showing that when an upper limb with a certain mass decelerates/accelerates sufficiently, it yields impulses on the body that cascade in various ways into the respiratory-vocal system. It entails a physical entanglement between body motions, respiration, and vocal activities. It is shown that vocal-entangled gestures are realized in infant vocal-motor babbling before any representational use of gesture develops. Similarly, an overview is given of vocal-entangled processes in non-human animals. They can frequently be found in rats, bats, birds, and a range of other species that developed even earlier in the phylogenetic tree. Thus, the origins of human gesture lie in biomechanics, emerging early in ontogeny and running deep in phylogeny.

Anticipatory regulation of cardiovascular system on the emergence of auditory-motor interaction in young infants

Humans develop auditory-motor interaction to produce a variety of rhythmic sounds using body movements, which are often produced and amplified with tools, such as drumming. The extended production of sounds allows us to express a wide range of emotions, accompanied by physiological changes. According to previous studies, even young infants enhance movements in response to auditory feedback. However, their exhibition of physiological adaptation on the emergence of auditory-motor interaction is unclear. We investigated the movement and cardiac changes associated with auditory feedback to spontaneous limb movements in 3-month-old infants. The results showed that infants increased the frequency of limb movements inducing auditory feedback, while they exhibited a more regular rhythm of the limb movements. Furthermore, heart rate increase associated with the limb movement was first inhibited immediately after the timing of the auditory feedback, which may reflect sustained attention to the auditory stimuli. Then, through auditory-motor experience, the heart rate increase was inhibited even prior to the auditory feedback, leading to suppression of the peak intensity of the heart rate increase. These findings suggest that young infants regulate the cardiovascular system as well as limb movements in anticipation of the auditory feedback. The anticipatory regulation associated with movement and attentional changes may contribute to reduced cardiovascular stress in auditory-motor interaction, and provide a developmental basis for more sophisticated goal-directed behavior of producing rhythmic sounds.

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

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

Promoting Adapted Physical Activity Regardless of Language Ability in Young Children With Autism Spectrum Disorder

Purpose: There is a relationship between motor and language skills in children with Autism Spectrum Disorder (ASD), but little work addresses the ramifications of this relationship for professionals who teach motor skills to this population. Within a motor skills intervention, this study probed the importance of language skills for motor intervention. We examined the relationship between motor and language skills at baseline, and then the relationship between baseline language skills and motor improvements resulting from the intervention. Method: Twenty children aged 4-6 years with ASD participated. Eleven children received 20 hr per week of motor intervention for 8 weeks. Nine children did not receive motor intervention. Language skills (Mullen Scales of Early Learning) and motor skills (Test of Gross Motor Development - 2) were assessed at baseline and post-intervention. Spearman correlations tested the associations between baseline language and baseline motor skills. This analysis was repeated in the intervention sample to test the association between baseline language level and response to intervention (motor skill changes from baseline to post-intervention). Results: Prior to intervention, locomotor skills are positively correlated (p < .001) with both receptive (rs = 0.827) and expressive (rs = 0.722) language skills. Similarly, object-control skills are positively correlated (rs < .001) with receptive (rs = 0.779) and expressive (rs = 0.729) language skills. However, those baseline language skills do not relate to motor change in the experimental group. Conclusion: These results suggest that motor programs may improve motor skills in children with ASD when language is supported, regardless of pre-program language ability.

Developmental changes of the central sulcus morphology in young children

The human brain grows rapidly in early childhood, reaching 95% of its final volume by age 6. Understanding brain growth in childhood is important both to answer neuroscience questions about anatomical changes in development, and as a comparison metric for neurological disorders. Metrics for neuroanatomical development including cortical measures pertaining to the sulci can be instrumental in early diagnosis, monitoring, and intervention for neurological diseases. In this paper, we examine the development of the central sulcus in children aged 12-60 months from structural magnetic resonance images. The central sulcus is one of the earliest sulci to develop at the fetal stage and is implicated in diseases such as Attention Deficit Hyperactive Disorder and Williams syndrome. We investigate the relationship between the changes in the depth of the central sulcus with respect to age. In our results, we observed a pattern of depth present early on, that had been previously observed in adults. Results also reveal the presence of a rightward depth asymmetry at 12 months of age at a location related to orofacial movements. That asymmetry disappears gradually, mostly between 12 and 24 months, and we suggest that it is related to the development of language skills.

Developmental Functional Modules in Infant Vocalizations

Purpose Developmental functional modules (DFMs) are biological modules that are defined by their structural (morphological), functional, or developmental elements, and, in some cases, all three of these. This review article considers the hypothesis that vocal development in the first year of life can be understood in large part with respect to DFMs that characterize the speech production system. Method Literature is reviewed on relevant embryology, orofacial reflexes, craniofacial muscle properties, stages of vocal development, and related topics to identity candidates for DFMs. Results The following DFMs are identified and described: laryngeal, pharyngo-laryngeal, mandibular, velopharyngeal, labial complex, and lingual complex. These DFMs and their submodules, considered along with phenomena such as rhythmic movements, account for several well-documented features of vocal development in the first year of life. The proposed DFMs, rooted in embryologic, histologic, and kinematic properties, serve as low-dimensional control variables for the developing vocal tract. Each DFM is semi-autonomous but interacts with other DFMs to produce patterns of vocal behavior. Discussion Considered in relation to contemporary profiles and models of vocal development in the first year of life, DFMs have interpretive and explanatory value. DFMs complement other approaches in the study of infant vocalizations and are grounded in biology.

Gesture-speech physics in fluent speech and rhythmic upper limb movements

It is commonly understood that hand gesture and speech coordination in humans is culturally and cognitively acquired, rather than having a biological basis. Recently, however, the biomechanical physical coupling of arm movements to speech vocalization has been studied in steady-state vocalization and monosyllabic utterances, where forces produced during gesturing are transferred onto the tensioned body, leading to changes in respiratory-related activity and thereby affecting vocalization F0 and intensity. In the current experiment (n = 37), we extend this previous line of work to show that gesture-speech physics also impacts fluent speech. Compared with nonmovement, participants who are producing fluent self-formulated speech while rhythmically moving their limbs demonstrate heightened F0 and amplitude envelope, and such effects are more pronounced for higher-impulse arm versus lower-impulse wrist movement. We replicate that acoustic peaks arise especially during moments of peak impulse (i.e., the beat) of the movement, namely around deceleration phases of the movement. Finally, higher deceleration rates of higher-mass arm movements were related to higher peaks in acoustics. These results confirm a role for physical impulses of gesture affecting the speech system. We discuss the implications of gesture-speech physics for understanding of the emergence of communicative gesture, both ontogenetically and phylogenetically.

Energy flows in gesture-speech physics: The respiratory-vocal system and its coupling with hand gestures

Expressive moments in communicative hand gestures often align with emphatic stress in speech. It has recently been found that acoustic markers of emphatic stress arise naturally during steady-state phonation when upper-limb movements impart physical impulses on the body, most likely affecting acoustics via respiratory activity. In this confirmatory study, participants (N = 29) repeatedly uttered consonant-vowel (/pa/) mono-syllables while moving in particular phase relations with speech, or not moving the upper limbs. This study shows that respiration-related activity is affected by (especially high-impulse) gesturing when vocalizations occur near peaks in physical impulse. This study further shows that gesture-induced moments of bodily impulses increase the amplitude envelope of speech, while not similarly affecting the Fundamental Frequency (F0). Finally, tight relations between respiration-related activity and vocalization were observed, even in the absence of movement, but even more so when upper-limb movement is present. The current findings expand a developing line of research showing that speech is modulated by functional biomechanical linkages between hand gestures and the respiratory system. This identification of gesture-speech biomechanics promises to provide an alternative phylogenetic, ontogenetic, and mechanistic explanatory route of why communicative upper limb movements co-occur with speech in humans.

A Six-Minute Measure of Vocalizations in Toddlers with Autism Spectrum Disorder

To improve early identification of autism spectrum disorder (ASD), we need objective, reliable, and accessible measures. To that end, a previous study demonstrated that a tablet-based application (app) that assessed several autism risk behaviors distinguished between toddlers with ASD and non-ASD toddlers. Using vocal data collected during this study, we investigated whether vocalizations uttered during administration of this app can distinguish among toddlers aged 16-31 months with typical development (TD), language or developmental delay (DLD), and ASD. Participant's visual and vocal responses were recorded using the camera and microphone in a tablet while toddlers watched movies designed to elicit behaviors associated with risk for ASD. Vocalizations were then coded offline. Results showed that (a) children with ASD and DLD were less likely to produce words during app administration than TD participants; (b) the ratio of syllabic vocalizations to all vocalizations was higher among TD than ASD or DLD participants; and (c) the rates of nonsyllabic vocalizations were higher in the ASD group than in either the TD or DLD groups. Those producing more nonsyllabic vocalizations were 24 times more likely to be diagnosed with ASD. These results lend support to previous findings that early vocalizations might be useful in identifying risk for ASD in toddlers and demonstrate the feasibility of using a scalable tablet-based app for assessing vocalizations in the context of a routine pediatric visit. LAY SUMMARY: Although parents often report symptoms of autism spectrum disorder (ASD) in infancy, we are not yet reliably diagnosing ASD until much later in development. A previous study tested a tablet-based application (app) that recorded behaviors we know are associated with ASD to help identify children at risk for the disorder. Here we measured how children vocalize while they watched the movies presented on the tablet. Children with ASD were less likely to produce words, less likely to produce speechlike sounds, and more likely to produce atypical sounds while watching these movies. These measures, combined with other behaviors measured by the app, might help identify which children should be evaluated for ASD. Autism Res 2020, 13: 1373-1382. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.

The Interdependence of Motor and Social Skill Development: Influence on Participation

Participation is a major outcome area for physical therapists serving young children with disabilities. Contemporary models of disability such as the International Classification of Function, developmental theories such as the system perspective, and evidence-based early childhood practices recognize the interdependence of developmental domains, and suggest that change in 1 area of development influences change in another. Physical therapy provided in naturally occurring activities and routines, considered the preferred service delivery method, promotes participation of young children with disabilities. Research indicates that: (1) children develop skills, become independent, and form relationships through participation; and (2) with developing skills, children can increasingly participate. The purpose of this Perspective article is to synthesize the literature examining the relationship between motor skill development and the social interaction dimension of participation in young children. Current research examining the influence of motor skill development on social interactions in children with autism spectrum disorder will be discussed, exemplifying the interdependence of developmental domains. Implications for physical therapist practice and recommendations for future research are provided.

The Development of Structured Vocalizations in Songbirds and Humans: A Comparative Analysis

Humans and songbirds face a common challenge: acquiring the complex vocal repertoire of their social group. Although humans are thought to be unique in their ability to convey symbolic meaning through speech, speech and birdsong are comparable in their acoustic complexity and the mastery with which the vocalizations of adults are acquired by young individuals. In this review, we focus on recent advances in the study of vocal development in humans and songbirds that shed new light on the emergence of distinct structural levels of vocal behavior and point to new possible parallels between both groups.

Effects of metronomic sounds on a self-paced tapping task in budgerigars and humans

The origin of rhythmic synchronization or entrainment to a musical beat in animals has been widely discussed. Parrots are suitable animals to examine the relationship between the capability of vocal learning and spontaneous rhythmic synchronization. In this study, budgerigars Melopsittacus undulatus learned to tap (peck) 2 keys alternately at a self-paced rate. Then, the metronomic sounds were played in the background during test sessions while the birds were performing the key pecking task, although they were not required to synchronize tap timing with the metronome. We found modest but significant effects of the metronome rhythms on the tap timing in some subjects. We also tested humans Homo sapiens using almost the same method. In contrast to the birds, a number of human subjects synchronized tap timing to the onset of the metronome without verbal or documented instructions. However, we failed to find an effect of the metronome on self-paced tap timing in some human subjects, although they were capable of rhythmic synchronization. This is the first report describing the effects of metronomic sounds on self-paced tapping in nonhuman vocal learners. This study introduces a new method that can be used in future research comparing birds that differ in vocal learning capacities, social structure, age, sex, hormonal status, and so on as part of examinations of the evolutionary foundations of beat processing.

Prosody in the Auditory and Visual Domains: A Developmental Perspective

The development of body movements such as hand or head gestures, or facial expressions, seems to go hand-in-hand with the development of speech abilities. We know that very young infants rely on the movements of their caregivers' mouth to segment the speech stream, that infants' canonical babbling is temporally related to rhythmic hand movements, that narrative abilities emerge at a similar time in speech and gestures, and that children make use of both modalities to access complex pragmatic intentions. Prosody has emerged as a key linguistic component in this speech-gesture relationship, yet its exact role in the development of multimodal communication is still not well understood. For example, it is not clear what the relative weights of speech prosody and body gestures are in language acquisition, or whether both modalities develop at the same time or whether one modality needs to be in place for the other to emerge. The present paper reviews existing literature on the interactions between speech prosody and body movements from a developmental perspective in order to shed some light on these issues.

Assessment of presentation patterns, clinical severity, and sensorial mechanism of tip-toe behavior in severe ASD subjects with intellectual disability: A cohort observational study

We assessed presentation patterns and characteristics of tip-toe behavior (TTB), more commonly known as toe walking, in a cohort of severe autism spectrum disorder (ASD) subjects with intellectual disability in two studies. The first study included 69 consecutive ASD subjects (57 males, mean age = 14 years-3.7 SD) under observation at our institute. A therapist assessed the presence of TTB during standing, walking, and running through direct observation and an interview with the subjects main caregiver. The prevalence of TTB was 32%. We found three clinical presentation patterns of TTB: (1) present when standing, walking and running (45.5%), (2) present when walking and running (18.4%), or (3) present only when running (36.4%). TTB subjects were more frequently nonverbal than those without TTB (72.7% vs. 44.6%-P = 0.03). On the other hand, no significant difference in ASD severity according to the ADOS scale was found between TTB and non-TTB subjects. In the second study, carried out in a subgroup of 14 ASD subjects (7 TTB and 7 non-TTB), we evidenced that a soft floor surface (foam mats) made a substantial difference in reducing the TTB phenomenon. TTB is frequently present in ASD individuals and may occur in three mutually exclusive modalities, which ultimately defines what is commonly known as toe walking. The presence of TTB seems correlated to the severity of language delay. Foot contact on soft surfaces reduces TTB both during static and/or dynamic tasks. Further evaluation is needed to clarify the potential pathophysiological implications of this phenomenon. Autism Res 2017, 10: 1547-1557. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Vowels Development in Babbling of typically developing 6-to-12-month old Persian-learning Infants

OBJECTIVES

Pre-linguistic vocalizations including early consonants, vowels, and their combinations into syllables are considered as important predictors of the speech and language development. The purpose of this study was to examine vowel development in babblings of normally developing Persian-learning infants.

METHODS

Eight typically developing 6-8-month-old Persian-learning infants (3 boys and 5 girls) participated in this 4-month longitudinal descriptive-analytic study. A weekly 30-60-minute audio- and video-recording was obtained at home from the comfort state vocalizations of infants and the mother-child interactions. A total of 74:02:03 hours of vocalizations were phonetically transcribed. Seven vowels comprising /i/,/e/,/a/,/u/,/o/,/ɑ/, and /ә/ were identified in the babblings. The inter-rater reliability was obtained for 20% of vocalizations. The data were analyzed by repeated measures ANOVA and Pearson's correlation coefficient using SPSS software version 20.

RESULTS

The results showed that two vowels /a/ (46.04) and /e/ (23.60) were produced with the highest mean frequency of occurrence, respectively. Regarding front/back dimension, the front vowels were the most prominent ones (71.87); in terms of height, low (46.78) and mid (32.45) vowels occurred maximally. A good inter-rater reliability was obtained (0.99, P < .01).

CONCLUSION

The increased frequency of occurrence of the low and mid front vowels in the current study was consistent with previous studies on the emergence of vowels in pre-linguistic vocalization in other languages.

Early gross motor skills predict the subsequent development of language in children with autism spectrum disorder

BACKGROUND

Motor milestones such as the onset of walking are important developmental markers, not only for later motor skills but also for more widespread social-cognitive development. The aim of the current study was to test whether gross motor abilities, specifically the onset of walking, predicted the subsequent rate of language development in a large cohort of children with autism spectrum disorder (ASD).

METHODS

We ran growth curve models for expressive and receptive language measured at 2, 3, 5 and 9 years in 209 autistic children. Measures of gross motor, visual reception and autism symptoms were collected at the 2 year visit. In Model 1, walking onset was included as a predictor of the slope of language development. Model 2 included a measure of non-verbal IQ and autism symptom severity as covariates. The final model, Model 3, additionally covaried for gross motor ability.

RESULTS

In the first model, parent-reported age of walking onset significantly predicted the subsequent rate of language development although the relationship became non-significant when gross motor skill, non-verbal ability and autism severity scores were included (Models 2 & 3). Gross motor score, however, did remain a significant predictor of both expressive and receptive language development.

CONCLUSIONS

Taken together, the model results provide some evidence that early motor abilities in young children with ASD can have longitudinal cross-domain influences, potentially contributing, in part, to the linguistic difficulties that characterise ASD. Autism Res 2016, 9: 993-1001. © 2015 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research.

Baby babbling at five months linked to sex hormone levels in early infancy

Gender-dependent differentiation of the brain at morphological, neurochemical and functional levels of organization have been shown to be primarily controlled by sex differences in gonadal hormone concentrations during pre- and early postnatal development. Indeed, previous studies have reported that pre- and perinatal hormonal environments influence brain development and, consequently, affect sex specific long-term language outcomes. Herein, we investigated whether postnatal surges of estrogen (estradiol) and androgen (testosterone) may predict properties of pre-speech babbling at five months. This study is the first attempt to investigate a possible correlation between sex hormones and infants' articulatory skills during the typical postnatal period of extended hormonal activity known as 'mini-puberty.' A hierarchical, multiple regression approach revealed a significant, robust positive relationship between 4-week concentrations of estradiol and individual articulatory skills. In contrast, testosterone concentrations at five months negatively correlated with articulatory skills at the same age in both boys and girls. Our findings reinforce the assumption of the importance of sex hormones for auditory-vocal development towards language in human infants.

Perception drives production across sensory modalities: A network for sensorimotor integration of visual speech

Sensory information is critical for movement control, both for defining the targets of actions and providing feedback during planning or ongoing movements. This holds for speech motor control as well, where both auditory and somatosensory information have been shown to play a key role. Recent clinical research demonstrates that individuals with severe speech production deficits can show a dramatic improvement in fluency during online mimicking of an audiovisual speech signal suggesting the existence of a visuomotor pathway for speech motor control. Here we used fMRI in healthy individuals to identify this new visuomotor circuit for speech production. Participants were asked to perceive and covertly rehearse nonsense syllable sequences presented auditorily, visually, or audiovisually. The motor act of rehearsal, which is prima facie the same whether or not it is cued with a visible talker, produced different patterns of sensorimotor activation when cued by visual or audiovisual speech (relative to auditory speech). In particular, a network of brain regions including the left posterior middle temporal gyrus and several frontoparietal sensorimotor areas activated more strongly during rehearsal cued by a visible talker versus rehearsal cued by auditory speech alone. Some of these brain regions responded exclusively to rehearsal cued by visual or audiovisual speech. This result has significant implications for models of speech motor control, for the treatment of speech output disorders, and for models of the role of speech gesture imitation in development.

Early influence of auditory stimuli on upper-limb movements in young human infants: an overview

Given that the auditory system is rather well developed at the end of the third trimester of pregnancy, it is likely that couplings between acoustics and motor activity can be integrated as early as at the beginning of postnatal life. The aim of the present mini-review was to summarize and discuss studies on early auditory-motor integration, focusing particularly on upper-limb movements (one of the most crucial means to interact with the environment) in association with auditory stimuli, to develop further understanding of their significance with regard to early infant development. Many studies have investigated the relationship between various infant behaviors (e.g., sucking, visual fixation, head turning) and auditory stimuli, and established that human infants can be observed displaying couplings between action and environmental sensory stimulation already from just after birth, clearly indicating a propensity for intentional behavior. Surprisingly few studies, however, have investigated the associations between upper-limb movements and different auditory stimuli in newborns and young infants, infants born at risk for developmental disorders/delays in particular. Findings from studies of early auditory-motor interaction support that the developing integration of sensory and motor systems is a fundamental part of the process guiding the development of goal-directed action in infancy, of great importance for continued motor, perceptual, and cognitive development. At-risk infants (e.g., those born preterm) may display increasing central auditory processing disorders, negatively affecting early sensory-motor integration, and resulting in long-term consequences on gesturing, language development, and social communication. Consequently, there is a need for more studies on such implications.

Review: The impact of motor development on typical and atypical social cognition and language: a systematic review

BACKGROUND

Motor development allows infants to gain knowledge of the world but its vital role in social development is often ignored.

METHOD

A systematic search for papers investigating the relationship between motor and social skills was conducted, including research in typical development and in Developmental Coordination Disorder, Autism Spectrum Disorders and Specific Language Impairment.

RESULTS

The search identified 43 studies, many of which highlighted a significant relationship between motor skills and the development of social cognition, language and social interactions.

CONCLUSIONS

This complex relationship requires more attention from researchers and practitioners, allowing the development of more tailored intervention techniques for those at risk of motor, social and language difficulties.

Spatiotemporal coupling between speech and manual motor actions

Much evidence has been found for pervasive links between the manual and speech motor systems, including evidence from infant development, deictic pointing, and repetitive tapping and speaking tasks. We expand on the last of these paradigms to look at intra- and cross-modal effects of emphatic stress, as well as the effects of coordination in the absence of explicit rhythm. In this study, subjects repeatedly tapped their finger and synchronously repeated a single spoken syllable. On each trial, subjects placed an emphatic stress on one finger tap or one spoken syllable. Results show that both movement duration and magnitude are affected by emphatic stress regardless of whether that stress is in the same domain (e.g., effects on the oral articulators when a spoken repetition is stressed) or across domains (e.g., effects on the oral articulators when a tap is stressed). Though the size of the effects differs between intra-and cross-domain emphases, the implementation of stress affects both motor domains, indicating a tight connection. This close coupling is seen even in the absence of stress, though it is highlighted under stress. The results of this study support the idea that implementation of prosody is not domain-specific but relies on general aspects of the motor system.

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.

Multimodality in infancy: vocal-motor and speech-gesture coordinations in typical and atypical development

From very early in life, expressive behavior is multimodal, with early behavioral coordinations being refined and strengthened over time as they become used for the communication of meaning. Of these communicative coordinations, those that involve gesture and speech have received perhaps the greatest empirical attention, but little is known about the developmental origins of the gesture-speech link. One possibility is that the origins of speech-gesture coordinations lie in hand-mouth linkages that are observed in the everyday sensorimotor activity of very young infants who do not yet use the hand or mouth to communicate meaning. In this article, I review evidence suggesting that the study of gesture-speech links and developmentally prior couplings between the vocal and motor systems in infancy can provide valuable insight into a number of later developments that reflect the cognitive interdependence of gesture and speech. These include aspects of language development and delay, the infant origins of the adult speech-gesture system, and early signs of autism spectrum disorder. Implications of these findings for studying the development of multimodal communication are considered.

Developing language in a developing body: the relationship between motor development and language development

ABSTRACTDuring the first eighteen months of life, infants acquire and refine a whole set of new motor skills that significantly change the ways in which the body moves in and interacts with the environment. In this review article, I argue that motor acquisitions provide infants with an opportunity to practice skills relevant to language acquisition before they are needed for that purpose; and that the emergence of new motor skills changes infants' experience with objects and people in ways that are relevant for both general communicative development and the acquisition of language. Implications of this perspective for current views of co-occurring language and motor impairments and for methodology in the field of child language research are also considered.

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.

Audio-vocal system regulation in children with autism spectrum disorders

Do children with autism spectrum disorders (ASD) respond similarly to perturbations in auditory feedback as typically developing (TD) children? Presentation of pitch-shifted voice auditory feedback to vocalizing participants reveals a close coupling between the processing of auditory feedback and vocal motor control. This paradigm was used to test the hypothesis that abnormalities in the audio-vocal system would negatively impact ASD compensatory responses to perturbed auditory feedback. Voice fundamental frequency (F(0)) was measured while children produced an /a/ sound into a microphone. The voice signal was fed back to the subjects in real time through headphones. During production, the feedback was pitch shifted (-100 cents, 200 ms) at random intervals for 80 trials. Averaged voice F(0) responses to pitch-shifted stimuli were calculated and correlated with both mental and language abilities as tested via standardized tests. A subset of children with ASD produced larger responses to perturbed auditory feedback than TD children, while the other children with ASD produced significantly lower response magnitudes. Furthermore, robust relationships between language ability, response magnitude and time of peak magnitude were identified. Because auditory feedback helps to stabilize voice F(0) (a major acoustic cue of prosody) and individuals with ASD have problems with prosody, this study identified potential mechanisms of dysfunction in the audio-vocal system for voice pitch regulation in some children with ASD. Objectively quantifying this deficit may inform both the assessment of a subgroup of ASD children with prosody deficits, as well as remediation strategies that incorporate pitch training.

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.

The relationship between reduplicated babble onset and laterality biases in infant rhythmic arm movements

This study examined changes in rhythmic arm shaking and laterality biases in infants observed longitudinally at three points: just prior to, at, and just following reduplicated babble onset. Infants (ranging in age from 4 to 9 months at babble onset) were videotaped at home as they played with two visually identical audible and silent rattles presented at midline for 1.5 min each. Rate of rattle shaking increased sharply from the pre-babble to the babble onset session; but there was no indication that this increase was specific to the right arm. This finding suggests that the link between babble onset and increased rhythmic arm activity may not be the product of language-specific mechanisms, but is rather part of a broader developmental process that is also perceptual and motor.

Variation in vocal-motor development in infant siblings of children with autism

In this study we examined early motor, vocal, and communicative development in a group of younger siblings of children diagnosed with autism (Infant Siblings). Infant Siblings and no-risk comparison later-born infants were videotaped at home with a primary caregiver each month from 5 to 14 months, with follow-up at 18 months. As a group, Infant Siblings were delayed in the onset of early developmental milestones and spent significantly less time in a greater number of postures, suggestive of relative postural instability. In addition, they demonstrated attenuated patterns of change in rhythmic arm activity around the time of reduplicated babble onset; and they were highly likely to exhibit delayed language development at 18 months.

Spontaneous facial motility in infancy: a 3D kinematic analysis

Early spontaneous orofacial movements have rarely been studied experimentally, though the motor experiences gained from these behaviors may influence the development of motor skills emerging for speech. This investigation quantitatively describes developmental changes in silent, spontaneous lip and jaw movements from 1 to 12 months of age using optically based 3D motion capture technology. Twenty-nine typically developing infants at five ages (1, 5, 7, 9, and 12 months) were studied cross-sectionally. Infants exhibited spontaneous facial movements at all ages studied. Several age-related changes were detected in lip and jaw kinematics: the occurrence of spontaneous movements increased, movement speed increased, the duration of movement epochs decreased and movement coupling among different facial regions increased. Additionally, evidence for stereotypic movements was not strong. The present findings suggest that, during the first year of life, early spontaneous facial movements undergo significant developmental change in the direction of skill development for speech.

Infant vocal-motor coordination: precursor to the gesture-speech system?

This study was designed to provide a general picture of infant vocal-motor coordination and test predictions generated by Iverson and Thelen's (1999) model of the development of the gesture-speech system. Forty-seven 6- to 9-month-old infants were videotaped with a primary caregiver during rattle and toy play. Results indicated an age-related increase in frequency of vocal-motor coordination, greater coordination with arm (specifically right arm) than leg or torso movements, and a temporal pattern similar to that in adult gesture-speech coproductions. Rhythmic vocalizations (consonant-vowel repetitions) were more likely to occur with than without rhythmic movement, and with rhythmic manual than with nonmanual activity, and the rate of vocal-manual coordination was higher in babblers than in prebabblers.

Research on speech motor control and its disorders: a review and prospective

This paper reviews issues in speech motor control and a class of communication disorders known as motor speech disorders. Speech motor control refers to the systems and strategies that regulate the production of speech, including the planning and preparation of movements (sometimes called motor programming) and the execution of movement plans to result in muscle contractions and structural displacements. Traditionally, speech motor control is distinguished from phonologic operations, but in some recent phonologic theories, there is a deliberate blurring of the boundaries between phonologic representation and motor functions. Moreover, there is continuing discussion in the literature as to whether a given motor speech disorder (especially apraxia of speech and stuttering) should be understood at the phonologic level, the motoric level, or both of these. The motor speech disorders considered here include: the dysarthrias, apraxia of speech, developmental apraxia of speech, developmental stuttering, acquired (neurogenic and psychogenic) stuttering, and cluttering.