Infant vocal productions coincide with body movements.

Producing recognizable words is a difficult motor task; a one-syllable word can require the coordination of over 80 muscles. Thus, it is not surprising that the development of word productions in infancy lags considerably behind receptive language and is a known limiting factor in language development. A large literature has focused on the vocal apparatus, its articulators, and language development. There has been limited study of the relations between non-speech motor skills and the quality of early speech productions. Here we present evidence that the spontaneous vocalizations of 9- to 24-month-old infants recruit extraneous, synergistic co-activations of hand and head movements and that the temporal precision of the co-activation of vocal and extraneous muscle groups tightens with age and improved recognizability of speech. These results implicate an interaction between the muscle groups that produce speech and other body movements and provide new empirical pathways for understanding the role of motor development in language acquisition. RESEARCH HIGHLIGHTS: The spontaneous vocalizations of 9- to 24-month-old infants recruit extraneous, synergistic co-activations of hand and head movements. The temporal precision of these hand and head movements during vocal production tighten with age and improved speech recognition. These results implicate an interaction between the muscle groups producing speech with other body movements. These results provide new empirical pathways for understanding the role of motor development in language acquisition.

Look before you reach: Fixation-reach latencies predict reaching kinematics in toddlers.

Research on infant and toddler reaching has shown evidence for motor planning after the initiation of the reaching action. However, the reach action sequence does not begin after the initiation of a reach but rather includes the initial visual fixations onto the target object occurring before the reach. We developed a paradigm that synchronizes head-mounted eye-tracking and motion capture to determine whether the latency between the first visual fixation on a target object and the first reaching movement toward the object predicts subsequent reaching behavior in toddlers. In a corpus of over one hundred reach sequences produced by 17 toddlers, we found that longer fixation-reach latencies during the pre-reach phase predicted slower reaches. If the slowness of an executed reach indicates reach difficulty, then the duration of pre-reach planning would be correlated with reach difficulty. However, no relation was found with pre-reach planning duration when reach difficulty was measured by usual factors and independent of reach duration. The findings raise important questions about the measurement of reach difficulty, models of motor control, and possible developmental changes in the relations between pre-planning and continuously unfolding motor plans throughout an action sequence.

The temporal structure of parent talk to toddlers about objects.

Toddlers learn words in the context of speech from adult social partners. The present studies quantitatively describe the temporal context of parent speech to toddlers about objects in individual real-world interactions. We show that at the temporal scale of a single play episode, parent talk to toddlers about individual objects is predominantly, but not always, clustered. Clustered speech is characterized by repeated references to the same object close in time, interspersed with lulls in speech about the object. Clustered temporal speech patterns mirror temporal patterns observed at longer timescales, and persisted regardless of play context. Moreover, clustered speech about individual novel objects predicted toddlers' learning of those objects' novel names. Clustered talk may be optimal for toddlers' word learning because it exploits domain-general principles of human memory and attention, principles that may have evolved precisely because of the clustered structure of natural events important to humans, including human behavior.

Coupling between prefrontal brain activity and respiratory sinus arrhythmia in infants and adults.

Self-regulation is an essential aspect of healthy child development. Even though infants depend on their caregivers for co-regulation during the first years, they begin to gain regulatory abilities through social interactions as well as their own developing agency and inhibitory control. These early regulatory abilities continue to increase with the development of both the prefrontal cortex and the vagal system. Importantly, theoretical accounts have suggested that the prefrontal cortex and the vagal system are linked through forward and backward feedback loops via the limbic system. Decreased coupling within this link is suggested to be associated with psychopathology. The primary goal of this study was to examine whether intrapersonal coupling of prefrontal brain activity and respiratory sinus arrhythmia is evident in infancy. Using the simultaneous assessment of functional near-infrared spectroscopy and electrocardiography, we used Cross-Recurrence Quantification Analysis to assess the coupling of prefrontal brain activity and respiratory sinus arrhythmia in 69 4- to 6-month-old infants and their mothers during a passive viewing condition. However, we did not find significant coupling between the PFC and RSA in infants and adult caregivers. Future studies could examine social contexts associated with greater emotional reactivity to deepen our understanding of the pathways involved in self-regulation.

Coupling between prefrontal brain activity and respiratory sinus arrhythmia in infants and adults.

Self-regulation is an essential aspect of healthy child development. Even though infants are dependent on their caregivers for co-regulation during the first years, they begin to gain early regulatory abilities through social interactions as well as their own cognitive development. These early regulatory abilities continue to increase with the maturation of both the prefrontal cortex and the vagal system. Importantly, theoretical accounts have suggested that the prefrontal cortex and the vagal system are linked through forward and backward feedback loops via the limbic system. Decreased coupling within this link is suggested to be associated with psychopathology. The primary goal of this study is to examine whether intrapersonal coupling of prefrontal brain activity and respiratory sinus arrythmia is evident in infancy. Using the simultaneous assessment of functional near-infrared spectroscopy and electrocardiography, we will use Cross-Recurrence Quantification Analysis to assess the coupling of prefrontal brain activity and respiratory sinus arrhythmia in 69 4-6-month-old infants and their mothers during rest. Understanding the developmental emergence of the neurobiological correlates of self- regulation will allow us to help identify neurodevelopmental risk factors.

Infant physiological activity and the early emergence of social communication.

Early in life, social engagement is facilitated by effective regulation during times of rest and stress. Physiological regulation during social play and in response to sudden environmental changes or social stressors may play an important role in sustaining social engagement in infancy and facilitate the acquisition of early social-communication skills. The aim of this study was to investigate the role of physiological activity during social play, including respiratory sinus arrhythsmia (RSA) and heart rate-defined attention, in the early emergence of social-communication skills. Using RSA as an index of vagal tone, we measured vagal tone, vagal suppression, and heart rate-defined sustained attention during a social interaction with a caregiver (i.e., the Still-Face procedure) in 21 infants aged 3-4 months. At 9 months, caregivers reported on their infant's early social-communication skills. Results suggest that RSA, RSA suppression, and heart rate-defined sustained attention to a caregiver are significantly associated with early-emerging social-communication skills at 9 months. In addition, RSA and heart rate-defined sustained attention during social play were highly related. Suppression of RSA during the Still-Face phase of the infant-caregiver interaction emerged as a particularly strong predictor of later-developing social-communication skills, including 9-month-olds' ability to use eye gaze, facial expression, and gestures to communicate.

Proximity and touch are associated with neural but not physiological synchrony in naturalistic mother-infant interactions.

Caregiver touch plays a vital role in infants' growth and development, but its role as a communicative signal in human parent-infant interactions is surprisingly poorly understood. Here, we assessed whether touch and proximity in caregiver-infant dyads are related to neural and physiological synchrony. We simultaneously measured brain activity and respiratory sinus arrhythmia of 4-6-month-old infants and their mothers (N=69 dyads) in distal and proximal joint watching conditions as well as in an interactive face-to-face condition. Neural synchrony was higher during the proximal than during the distal joint watching conditions, and even higher during the face-to-face interaction. Physiological synchrony was highest during the face-to-face interaction and lower in both joint watching conditions, irrespective of proximity. Maternal affectionate touch during the face-to-face interaction was positively related to neural but not physiological synchrony. This is the first evidence that touch mediates mutual attunement of brain activities, but not cardio-respiratory rhythms in caregiver-infant dyads during naturalistic interactions. Our results also suggest that neural synchrony serves as a biological pathway of how social touch plays into infant development and how this pathway could be utilized to support infant learning and social bonding.

Head and eyes: Looking behavior in 12- to 24-month-old infants.

This study demonstrates evidence for a foundational process underlying active vision in older infants during object play. Using head-mounted eye-tracking and motion capture, looks to an object are shown to be tightly linked to and synchronous with a stilled head, regardless of the duration of gaze, for infants 12 to 24 months of age. Despite being a developmental period of rapid and marked changes in motor abilities, the dynamic coordination of head stabilization and sustained gaze to a visual target is developmentally invariant during the examined age range. The findings indicate that looking with an aligned head and eyes is a fundamental property of human vision and highlights the importance of studying looking behavior in freely moving perceivers in everyday contexts, opening new questions about the role of body movement in both typical and atypical development of visual attention.

Associations between infant-mother physiological synchrony and 4- and 6-month-old infants' emotion regulation.

In this study we assessed whether physiological synchrony between infants and mothers contributes to infants' emotion regulation following a mild social stressor. Infants between 4 and 6 months of age and their mothers were tested in the face-to-face-still-face paradigm and were assessed for behavioral and physiological self-regulation during and following the stressor. Physiological synchrony was calculated from a continuous measure of respiratory sinus arrhythmia (RSA) enabling us to cross-correlate the infants' and mothers' RSA responses. Without considering physiological synchrony, the evidence suggested that infants' distress followed the prototypical pattern of increasing during the Still Face episode and then decreasing during the reunion episode. Once physiological synchrony was added to the model, we observed that infants' emotion regulation improved if mother-infant synchrony was positive, but not if it was negative. This result was qualified further by whether or not infants suppressed their RSA response during the Still Face episode. In sum, these findings highlight how individual differences in infants' physiological responses contribute significantly to their self-regulation abilities.

A method for measuring dynamic respiratory sinus arrhythmia (RSA) in infants and mothers.

The measurement of respiratory sinus arrythmia (RSA) in infants, children and adults is critical to the study of physiological regulation, and more recently, interpersonal physiological covariation, but it has been impeded by methods that limit its resolution to 30 s or longer. Recent analytical developments have suggested methods for studying dynamic RSA in adults, and we have extended this work to the study of infants and mothers. In the current paper, we describe a new analytical strategy for estimating RSA time series for infants and adults. Our new method provides a means for studying physiological synchrony in infant-mother dyads that offers some important advantages relative to existing methods that use inter-beat-intervals (e.g. Feldman, Magori-Cohen, Galili, Singer, & Louzoun, 2011). In the middle sections of this paper, we offer a brief tutorial on calculating RSA continuously with a sliding window and review the empirical evidence for determining the optimal window size. In order to confirm the reliability of our results, we briefly discuss testing synchrony by randomly shuffling the dyads to control for spurious correlations, and also by using a bootstrapping technique for calculating confidence intervals in the cross-correlation function. One important implication that emerges from applying this method is that it is possible to measure both positive and negative physiological synchrony and that these categorical measures are differentially predictive of future outcomes.

Cooperation in sound and motion: Complexity matching in collaborative interaction.

Complex behaviors are layered with processes across timescales that must be coordinated with each other to accomplish cooperative goals. Complexity matching is the coordination of nested layers of behaviors across individuals. We hypothesize that complexity matching extends across individuals and their respective layers of processes when cooperating in joint tasks. We measured coordination in a joint tower building task through the layers of sound and movement patterns produced by partners and found that partners built higher towers when their sound patterns fell into more similar relations with each other across timescales, as measured by complexity matching. Our findings shed light on the function of complexity matching and lead to new hypotheses about multiscale coordination and communication. We discuss how complexity matching encompasses flexible and complementary dynamics between partners that support complex acts of human coordination. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

What are the building blocks of parent-infant coordinated attention in free-flowing interaction?

The present article investigated the composition of different joint gaze components used to operationalize various types of coordinated attention between parents and infants and which types of coordinated attention were associated with future vocabulary size. Twenty-five 9-month-old infants and their parents wore head-mounted eye trackers as they played with objects together. With high-density gaze data, a variety of coordinated attention bout types were quantitatively measured by combining different gaze components, such as mutual gaze, joint object looks, face looks, and triadic gaze patterns. The key components of coordinated attention that were associated with vocabulary size at 12 and 15 months included the simultaneous combination of parent triadic gaze and infant object looking. The results from this article are discussed in terms of the importance of parent attentional monitoring and infant sustained attention for language development.

Finding Structure in Time: Visualizing and Analyzing Behavioral Time Series.

The temporal structure of behavior contains a rich source of information about its dynamic organization, origins, and development. Today, advances in sensing and data storage allow researchers to collect multiple dimensions of behavioral data at a fine temporal scale both in and out of the laboratory, leading to the curation of massive multimodal corpora of behavior. However, along with these new opportunities come new challenges. Theories are often underspecified as to the exact nature of these unfolding interactions, and psychologists have limited ready-to-use methods and training for quantifying structures and patterns in behavioral time series. In this paper, we will introduce four techniques to interpret and analyze high-density multi-modal behavior data, namely, to: (1) visualize the raw time series, (2) describe the overall distributional structure of temporal events (Burstiness calculation), (3) characterize the non-linear dynamics over multiple timescales with Chromatic and Anisotropic Cross-Recurrence Quantification Analysis (CRQA), (4) and quantify the directional relations among a set of interdependent multimodal behavioral variables with Granger Causality. Each technique is introduced in a module with conceptual background, sample data drawn from empirical studies and ready-to-use Matlab scripts. The code modules showcase each technique's application with detailed documentation to allow more advanced users to adapt them to their own datasets. Additionally, to make our modules more accessible to beginner programmers, we provide a "Programming Basics" module that introduces common functions for working with behavioral timeseries data in Matlab. Together, the materials provide a practical introduction to a range of analyses that psychologists can use to discover temporal structure in high-density behavioral data.

Children and adolescents with cerebral palsy flexibly adapt grip control in response to variable task demands.

BACKGROUND: Children and adolescents with cerebral palsy demonstrate impairments in grip control with associated limitations in functional grasp. Previous work in cerebral palsy has focused on grip control using relatively predictable task demands, a feature which may limit generalizability of those study results in light of recent evidence in typically developing adults suggesting that grip control strategies are task-dependent. The purpose of this study was to determine whether and how varying upper extremity task demands affect grip control in children and adolescents with cerebral palsy. METHODS: Children and adolescents with mild spastic cerebral palsy (n = 10) and age- and gender-matched typically developing controls (n = 10) participated. Participants grasped an object while immersed in a virtual environment displaying a moving target and a virtual representation of the held object. Participants aimed to track the target by maintaining the position of the virtual object within the target as it moved in predictable and unpredictable trajectories. FINDINGS: Grip control in children with cerebral palsy was less efficient and less responsive to object load force than in typically developing children, but only in the predictable trajectory condition. Both groups of participants demonstrated more responsive grip control in the unpredictable compared to the predictable trajectory condition. INTERPRETATION: Grip control impairments in children with cerebral palsy are task-dependent. Children and adolescents with cerebral palsy demonstrated commonly observed grip impairments in the predictable trajectory condition. Unpredictable task demands, however, appeared to attenuate impairments and, thus, could be exploited in the design of therapeutic interventions.

How do infants start learning object names in a sea of clutter?

Infants are powerful learners. A large corpus of experimental paradigms demonstrate that infants readily learn distributional cues of name-object co-occurrences. But infants' natural learning environment is cluttered: every heard word has multiple competing referents in view. Here we ask how infants start learning name-object co-occurrences in naturalistic learning environments that are cluttered and where there is much visual ambiguity. The framework presented in this paper integrates a naturalistic behavioral study and an application of a machine learning model. Our behavioral findings suggest that in order to start learning object names, infants and their parents consistently select a set of a few objects to play with during a set amount of time. What emerges is a frequency distribution of a few toys that approximates a Zipfian frequency distribution of objects for learning. We find that a machine learning model trained with a Zipf-like distribution of these object images outperformed the model trained with a uniform distribution. Overall, these findings suggest that to overcome referential ambiguity in clutter, infants may be selecting just a few toys allowing them to learn many distributional cues about a few name-object pairs.

Gaze in Action: Head-mounted Eye Tracking of Children's Dynamic Visual Attention During Naturalistic Behavior.

Young children's visual environments are dynamic, changing moment-by-moment as children physically and visually explore spaces and objects and interact with people around them. Head-mounted eye tracking offers a unique opportunity to capture children's dynamic egocentric views and how they allocate visual attention within those views. This protocol provides guiding principles and practical recommendations for researchers using head-mounted eye trackers in both laboratory and more naturalistic settings. Head-mounted eye tracking complements other experimental methods by enhancing opportunities for data collection in more ecologically valid contexts through increased portability and freedom of head and body movements compared to screen-based eye tracking. This protocol can also be integrated with other technologies, such as motion tracking and heart-rate monitoring, to provide a high-density multimodal dataset for examining natural behavior, learning, and development than previously possible. This paper illustrates the types of data generated from head-mounted eye tracking in a study designed to investigate visual attention in one natural context for toddlers: free-flowing toy play with a parent. Successful use of this protocol will allow researchers to collect data that can be used to answer questions not only about visual attention, but also about a broad range of other perceptual, cognitive, and social skills and their development.

A View of Their Own: Capturing the Egocentric View of Infants and Toddlers with Head-Mounted Cameras.

Infants and toddlers view the world, at a basic sensory level, in a fundamentally different way from their parents. This is largely due to biological constraints: infants possess different body proportions than their parents and the ability to control their own head movements is less developed. Such constraints limit the visual input available. This protocol aims to provide guiding principles for researchers using head-mounted cameras to understand the changing visual input experienced by the developing infant. Successful use of this protocol will allow researchers to design and execute studies of the developing child's visual environment set in the home or laboratory. From this method, researchers can compile an aggregate view of all the possible items in a child's field of view. This method does not directly measure exactly what the child is looking at. By combining this approach with machine learning, computer vision algorithms, and hand-coding, researchers can produce a high-density dataset to illustrate the changing visual ecology of the developing infant.

The Bursts and Lulls of Multimodal Interaction: Temporal Distributions of Behavior Reveal Differences Between Verbal and Non-Verbal Communication.

Recent studies of naturalistic face-to-face communication have demonstrated coordination patterns such as the temporal matching of verbal and non-verbal behavior, which provides evidence for the proposal that verbal and non-verbal communicative control derives from one system. In this study, we argue that the observed relationship between verbal and non-verbal behaviors depends on the level of analysis. In a reanalysis of a corpus of naturalistic multimodal communication (Louwerse, Dale, Bard, & Jeuniaux, ), we focus on measuring the temporal patterns of specific communicative behaviors in terms of their burstiness. We examined burstiness estimates across different roles of the speaker and different communicative modalities. We observed more burstiness for verbal versus non-verbal channels, and for more versus less informative language subchannels. Using this new method for analyzing temporal patterns in communicative behaviors, we show that there is a complex relationship between verbal and non-verbal channels. We propose a "temporal heterogeneity" hypothesis to explain how the language system adapts to the demands of dialog.

Developmentally Changing Attractor Dynamics of Manual Actions with Objects in Late Infancy.

Human infants interact with the environment through a growing and changing body and their manual actions provide new opportunities for exploration and learning. In the current study, a dynamical systems approach was used to quantify and characterize the early motor development of limb effectors during bouts of manual activity. Many contemporary theories of motor development emphasize sources of order in movement over developmental time. However, little is known about the dynamics of manual actions during the first two years of life, a period of development with dramatic anatomical changes resulting in new opportunities for action. Here, we introduce a novel analytical protocol for estimating properties of attractor regions using motion capture. We apply this new analysis to a longitudinal corpus of manual actions during sessions of toy play across the first two years of life. Our results suggest that the size of attractor regions for manual actions increases across development and that infants spend more time inside the attractor region of their movements during bouts of manual actions with objects. The sources of order in manual actions are discussed in terms of changing attractor dynamics across development.