Infant locomotion shapes proximity to adults during everyday play in the U.S.

Learning to walk expands infants’ access to the physical environment and prompts changes in their communicative behaviors. However, little is known about whether walking also shapes infants’ proximity to their adult social partners during everyday activities at home. Here we followed 89 infants (42 boys, 47 girls; 92% White, not Hispanic or Latino) longitudinally and documented connections between infant locomotion and infant-adult proximity on two timescales: (1) across developmental time, by comparing data from a session when infants could only crawl to a later session when they could walk (M walk onset = 12.15 months, range = 8-15); and (2) in real time, by testing whether the amount of time that infants spent in motion (regardless of their locomotor status) related to their interpersonal distance to adults. The developmental transition to walking corresponded to a significant, but modest, decrease in infant-adult proximity. Infants’ moment-to-moment locomotion, however, was strongly related to patterns of interpersonal distance: infants who spent more time in motion spent less time near adults and instigated more proximity transitions, resulting in shorter and more dispersed bouts of proximity throughout sessions. Findings shed new light on how infants’ motor achievements can reverberate across other domains of development, and how changes in infant development that researchers often observe over months arise from infants’ moment-to-moment experiences.     

The mountain stream of infant development

Development is complex. It encompasses interacting domains, at multiple levels, across nested time scales. Embracing the complexity of development—while addressing the challenges inherent to studying infants—requires researchers to make tough decisions about what to study, why, how, where, and when. My own view is inspired by a developmental systems approach, and echoed in Esther Thelen's (2005) mountain stream metaphor. Like a river that carves its course, the active infant navigates the social and physical environment and generates rich inputs that propel learning and development. Drawing from my experiences, I offer some recommendations to guide research on infants. I encourage researchers to embrace discovery science; to observe infants in ecologically valid settings; to recognize the active and adaptive nature of infant behavior; to break down silos and consider the nonobvious; and to adopt full transparency in all aspects of research. I draw on cascading influences in infant play, language, and motor domains to illustrate the value of a bottom-up, cross-domain, collaborative approach.     

Relations Between Mother‐Child Interactions and the Neural Correlates of Face Processing in 6‐Month‐Olds

Developmental studies of face processing have revealed age‐related changes in how infants allocate neurophysiological resources to the face of a caregiver and an unfamiliar adult. We hypothesize that developmental changes in how infants interact with their caregiver are related to the changes in brain response. We studied 6‐month‐olds because this age is frequently noted in the behavioral and neurophysiological literature as a time of transition in which infants begin to discriminate more readily between caregivers and unfamiliar adults. We used infants' behavioral responses to an original behavioral paradigm to predict event‐related potential (ERP) responses to pictures of the mother's face and a stranger's face in the same group of participants. Our results suggest that individual differences in infants' proximity‐seeking behaviors during interactions with the mother correlate with their neurophysiological responses to the mother's face as opposed to an unfamiliar face for the Nc component of the ERP. These results have implications for understanding the role of the changing infant‐caregiver relationship on the development of the face processing system in early infancy.     

Exploring in Silence: Hearing and Deaf Infants Explore Objects Differently Before Cochlear Implantation

Infant development has rarely been informed by the behavior of infants with sensory differences despite increasing recognition that infant behavior itself creates sensory learning opportunities. The purpose of this study of object exploration was to compare the behavior of hearing and deaf infants, with and without cochlear implants, in order to identify the effects of profound sensorineural hearing loss on infant exploration before cochlear implantation, the behavioral effects of access to auditory feedback after cochlear implantation, and the sensory motivation for exploration behaviors performed by hearing infants as well. The results showed that 9‐month‐old deaf infants explored objects as often as hearing infants but they used systematically different approaches and less variation before compared to after cochlear implantation. Potential associations between these early experiences and later learning are discussed in the context of embodied developmental theory, comparative studies, and research with adults. The data call for increased recognition of the active sensorimotor nature of infant learning and future research that investigates differences in sensorimotor experience as potential mechanisms in later learning and sequential memory development.     

Infant motor development predicts the dynamics of movement during sleep

The characteristics of infant sleep change over the first year. Generally, infants wake and move less at night as they grow older. However, acquisition of new motor skills leads to temporary increases in night waking and movement at night. Indeed, sleep-dependent movement at night is important for sensorimotor development. Nevertheless, little is known about how movement during sleep changes as infants accrue locomotor experience. The current study investigated whether infant sleep and movement during sleep were predicted by infants' walking experience. Seventy-eight infants wore an actigraph to measure physical activity during sleep. Parents reported when their infants first walked across a room >10 feet without stopping or falling. Infants in the midst of walking skill acquisition had worse sleep than an age-group estimate. Infants with more walk experience had more temporally sporadic movement during sleep and a steeper hourly increase in physical activity over the course of the night. Ongoing motor skill consolidation changes the characteristics of movement during sleep and may alter sleep state-dependent memory consolidation. We propose a model whereby changes in gross motor activity during night sleep reflect movement-dependent consolidation.     

Stabilities of infant behaviors and maternal responses to them

Consistency in the order of individuals in a group across substantial lengths of time—stability—is a central concept in developmental science for several reasons. Stability underscores the meaningfulness of individual differences in psychological phenomena; stability informs about the origins, nature, and overall developmental course of psychological phenomena; stability signals individual status and so affects the environment, experience, and development; stability has both theoretical and clinical implications for individual functioning; and stability helps to establish that a measure constitutes a consequential individual‐differences metric. In this three‐wave prospective longitudinal study (Ns = 40 infants and mothers), we examined stabilities of individual variation in multiple infant behaviors and maternal responses to them across infant ages 10, 14, and 21 months. Medium to large effect size stabilities in infant behaviors and maternal responses emerged, but both betray substantial amounts of unshared variance. Documenting the ontogenetic trajectories of infant behaviors and maternal responses helps to elucidate the nature and structure of early human development.     

Handedness as a major determinant of lateral bias in human functional cradling

Studies examining infant cradling have almost uniformly concluded with a general human left-side bias for cradling, indicating that people prefer to hold an infant to the left of their body. Explanations for the notion of the left-side cradling bias have traditionally been searched for in a variety of factors, for example, in terms of maternal heartbeat, genetic factors, in the form of an ear asymmetry where auditory information is perceived faster through the left ear, as a result of a right hemispheric functional specialization for perception of emotions and faces, and in identifying a motor bias of the infant, such as the tendency of newborn infants to lie with the face to the right when placed supine. Interestingly, handedness is generally considered an inadequate explanation for the lateralized cradling bias, despite it being an intuitively plausible one. In this brief review, I put forward the cradler's handedness as the most convincing and elegant determinant of the cradling bias. This explanation is consistent with a developmental cascades' framework where the cradling bias can be understood as the result of a multitude of factors across a range of levels and systems.     

Common Mechanisms in Infant and Adult Category Learning

Computational models of infant categorization often fail to elaborate the transitional mechanisms that allow infants to achieve adult performance. In this article, we apply a successful connectionist model of adult category learning to developmental data. The Supervised and Unsupervised Stratified Adaptive Incremental Network (SUSTAIN) model is able to account for the emergence of infants' sensitivity to correlated attributes (e.g., has wings and can fly). SUSTAIN offers 2 complimentary explanations of the developmental trend. One explanation centers on memory storage limitations, whereas the other focuses on limitations in perceptual systems. Both explanations parallel published findings concerning the cognitive and sensory limitations of infants. SUSTAIN's simulations suggest that conceptual development follows a continuous and smooth trajectory despite qualitative changes in behavior and that the mechanisms that underlie infant and adult categorization might not differ significantly.     

Acoustic Packaging of Action Sequences by Infants

This study investigated whether acoustic input, in the form of infant‐directed speech, influenced infants' segmenting of action sequences. Thirty‐two 7.5‐ to 11.5‐month‐old infants were familiarized with video sequences made up of short action clips. Narration coincided with portions of the action stream to package certain pairs of clips together. At test, packaged and nonpackaged pairs of actions were presented side by side in silence. Narration heard during familiarization influenced how infants viewed the action units, such that at test, infants older than 9.5 months (but not younger) looked longer at the nonpackaged than the packaged action sequences. The role of infant‐directed speech as well as other types of acoustic input in assisting infants' processing of action is discussed.     

Families,Not Parents,Differ: Development of Communication in Finnish Infants

This longitudinal study on Finnish families was conducted to identify developmental differences in family‐level communication among mothers, fathers, and their infants during the second half of the infant's first year, and associations with infants' later language and communicative skills. We examined coregulated communication of parent‐infant dyads during 5‐min laboratory play sessions at 7 and 11 months. Few differences in mutually regulated communicative exchanges emerged between maternal and paternal dyads, and few developmental changes were found across the whole sample. Families with different communication profiles were identified, and changes rather than stability characterized communicative development at the family level. The family‐level differences at 7 months predicted variation in children's language and communicative skills at 14 months.     

Environmental Influences on Infants’ Native Vowel Discrimination: The Case of Talker Number in Daily Life

Both quality and quantity of speech from the primary caregiver have been found to impact language development. A third aspect of the input has been largely ignored: the number of talkers who provide input. Some infants spend most of their waking time with only one person; others hear many different talkers. Even if the very same words are spoken the same number of times, the pronunciations can be more variable when several talkers pronounce them. Is language acquisition affected by the number of people who provide input? To shed light on the possible link between how many people provide input in daily life and infants’ native vowel discrimination, three age groups were tested: 4‐month‐olds (before attunement to native vowels), 6‐month‐olds (at the cusp of native vowel attunement) and 12‐month‐olds (well attuned to the native vowel system). No relationship was found between talker number and native vowel discrimination skills in 4‐ and 6‐month‐olds, who are overall able to discriminate the vowel contrast. At 12 months, we observe a small positive relationship, but further analyses reveal that the data are also compatible with the null hypothesis of no relationship. Implications in the context of infant language acquisition and cognitive development are discussed.     

ENGINEERING THE ENTREPRENEURIAL INFANT: BRAIN SCIENCE,INFANT DEVELOPMENT TOYS,AND GOVERNMENTALITY

This essay re-situates current neurological research on infant brain development in terms of a matrix of cultural practices and pre-occupations. It contends that infant ‘brain science’ functions – in conjunction with the marketing promises of developmental toy manufacturers – as a form of ‘ritual magic’ (Nelson-Rowe, 1994) that ensures the transformation of ‘normal’ infants into idealized entrepreneurial subjects. Simultaneously, the discourse and practices of brain science extend and legitimize the extension of (Foucauldian) governmentality over lower income populations, which are perceived as threatening social and state security.     

Consequences of Eye Color,Positioning, and Head Movement for Eye‐Tracking Data Quality in Infant Research

Eye tracking has become a valuable tool for investigating infant looking behavior over the last decades. However, where eye‐tracking methodology and achieving high data quality have received a much attention for adult participants, it is unclear how these results generalize to infant research. This is particularly important as infants behave different from adults in front of the eye tracker. In this study, we investigated whether eye physiology, positioning, and infant behavior affect measures of eye‐tracking data quality: accuracy, precision, and data loss. We report that accuracy and precision are lower, and more data loss occurs for infants with bluish eye color compared to infants with brownish eye color. Moreover, accuracy was lower for infants positioned in a high chair or in the parents' lap compared to infants positioned in a baby seat. Finally, precision decreased and data loss increased as a function of time. We highlight the importance of data quality when comparing multiple groups, as differences in data quality can affect eye‐tracking measures. In addition, we investigate how two different measures to quantify infant movement influence eye‐tracker data quality. These findings might help researchers with data collection and help manufacturers develop better eye‐tracking systems for infants.     

Young Infants' Behavioral Reactivity to Mild Perturbation: Developmental Continuity,Stability, and Organization

This study investigated the developmental continuity, stability, and organization of infants' behavioral response to mild stress from 1 to 3 months of age. Changes in infant stress reactivity were expected to coincide with a suspected neurobiological shift around the 2nd month. A total of 53 infants and their mothers participated in this study. At 1 and 3 months, infants' stress reactivity to mild perturbation was assessed by withdrawing a pacifier during nonnutritive sucking. Infant baseline heart rate activity and maternal reports of infant temperament were also obtained. Focusing on facial and vocal negativity, behavioral measures of infant reactivity to pacifier withdrawal were coded from videos. Results showed that developmental continuity and individual instability characterized changes in infant stress reactivity over the 2nd‐month transition. Developmental reorganization was also evidenced by changes in the direction and magnitude of infant stress reactivity in relation to baseline heart period and maternal temperament ratings, respectively. These findings provide direct supporting evidence for the contention that changes in infant stress reactivity to mild perturbation may be a function of developmental shifts in underlying neurobiological mechanisms in early infancy.     

Four‐Month‐Olds' Discrimination of Voice Changes in Multimodal Displays as a Function of Discrimination Protocol

Past studies have found equivocal support for the ability of young infants to discriminate infant‐directed (ID) speech information in the presence of auditory‐only versus auditory + visual displays (faces + voices). Generally, younger infants appear to have more difficulty discriminating a change in the vocal properties of ID speech when they are accompanied by faces. Forty 4‐month‐old infants were tested using either an infant‐controlled habituation procedure (Experiment 1) or a fixed‐trial habituation procedure (Experiment 2). The prediction was that the infant‐controlled habituation procedure would be a more sensitive measure of infant attention to complex displays. The results indicated that 4‐month‐old infants discriminated voice changes in dynamic face + voice displays depending on the order in which they were viewed during the infant‐controlled habituation procedure. In contrast, no evidence of discrimination was found in the fixed‐trial procedure. The findings suggest that the selection of experimental methodology plays a significant role in the empirical observations of infant perceptual abilities.     

Multiple Coordination Patterns in Infant and Adult Vocalizations

The study of vocal coordination between infants and adults has led to important insights into the development of social, cognitive, emotional, and linguistic abilities. We used an automatic system to identify vocalizations produced by infants and adults over the course of the day for fifteen infants studied longitudinally during the first 2 years of life. We measured three different types of vocal coordination: coincidence‐based, rate‐based, and cluster‐based. Coincidence‐based coordination and rate‐based coordination are established measures in the developmental literature. Cluster‐based coordination is new and measures the strength of matching in the degree to which vocalization events occur in hierarchically nested clusters. We investigated whether various coordination patterns differ as a function of vocalization type, whether different coordination patterns provide unique information about the dynamics of vocal interaction, and how the various coordination patterns each relate to infant age. All vocal coordination patterns displayed greater coordination for infant speech‐related vocalizations, adults adapted the hierarchical clustering of their vocalizations to match that of infants, and each of the three coordination patterns had unique associations with infant age. Altogether, our results indicate that vocal coordination between infants and adults is multifaceted, suggesting a complex relationship between vocal coordination and the development of vocal communication.     

An Emerging Consensus: Younger and Cohen Revisited

From Aesop to Sun Tzu, the importance of working together has long been acknowledged. Yet as long as cooperation has existed, so have the difficulties associated with it. Pooling two fields might mean twice the power, but this union also brings twice the jargon, twice the competing theories, and twice the head butting. Nonetheless, in this collection, researchers have made a heroic effort to set aside their theoretical differences to produce three computational models for the influential set of empirical data showing that young infants have difficulty detecting correlations among features (Younger & Cohen, 1983, 1986). Specifically, Gureckis and Love (2004/this issue) fit a well‐developed adult‐learning model to the infant work (down to the exact order and number of test trials) in support of a common mechanism underlying categorization. Shultz and Cohen (2004/this issue) vary depth of processing in a cascade correlation network to show how older infants learn more than younger infants from the same amount of exposure. And Westermann and Mareschal (2004/this issue) introduce a model for their representational acuity hypothesis, which explains qualitative shifts as a decrease in the size of neural receptive fields. This commentary takes stock of this attempt at unifying computational modeling and developmental data by identifying common themes, clarifying points of disagreement, and providing a synthesis for this work.     

Maternal Sensitivity and the Learning‐Promoting Effects of Depressed and Nondepressed Mothers' Infant‐Directed Speech

The hypothesis that aspects of current mother‐infant interactions predict an infant's response to maternal infant‐directed speech (IDS) was tested. Relative to infants of nondepressed mothers, those of depressed mothers acquired weaker voice‐face associations in response to their own mothers' IDS in a conditioned‐attention paradigm, although this was partially attributable to demographic differences between the 2 groups. The extent of fundamental frequency modulation (ΔF₀) in maternal IDS was smaller for infants of depressed than nondepressed mothers, but did not predict infant learning. However, Emotional Availability Scale ratings of maternal sensitivity, coded from videotapes of mothers and infants engaged in a brief play interaction, were significant predictors of infant learning, even after maternal depression, its demographic correlates, and antidepressant medication use had been taken into account. These findings are consistent with a role for experience‐dependent processes in determining the effects of IDS on infant learning.     

Child Care as a Relational Context for Early Development: Research in Neurobiology and Emerging Roles for Social Work

The quality of child care in the United States is an important social problem, particularly for economically vulnerable families. This is highlighted by multidisciplinary research on the importance of early caregiving as a determinant of child health and wellbeing. This article examines center-based child care as an important relational and developmental context for infants and young children. Through an integration of psychosocial studies and emerging research in the cognitive neurosciences, this paper describes how developmental research on early emotional development can be utilized to inform our understanding of child care as a critical social and interpersonal context for infants and young children. In particular, this paper examines research on early interpersonal experience as a determinant of the capacity for affect regulation. Focusing on the application of theory to practice, this paper discusses the relevance of this research to informed direct practice, advocacy and program development.     

Affects of unease: mother–infant separation among professional Indonesian women working in Singapore

The extent of systemic forms of mother–child separation has received insufficient attention in research on migrant families. In this article, I explore the little‐studied phenomenon of mother–infant separation among professional women migrants. I draw from in‐depth interviews with Indonesian professional women working in Singapore who have lived apart from their infant children to pursue work and education. Narratives of separation illustrate a complex transnational network of care built around an availability of support offered by spouses or extended kin. Women experience unease about separation, which emerges in how they talk about their absent infants. Mothers articulate ambivalence about the potential cost of their decisions, positing infants as able to pass judgement on them, with potential rejection and disengagement causing them potent concerns. The unease of these mothers moderates claims that transnational separation is readily managed and highlights the ambiguity embedded in an increasingly common form of transnational mother–child separation.