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.     

A New Perspective on Neonatal Smiling: Differences Between the Judgments of Expert Coders and Naive Observers

To better understand the form and recognizability of neonatal smiling, 32 newborns (14 girls; M = 25.6 hr) were videorecorded in the behavioral states of alertness, drowsiness, active sleep, and quiet sleep. Baby Facial Action Coding System coding of both lip corner raising (simple or non‐Duchenne) and lip corner raising with cheek raising (Duchenne smile) was followed by a smile recognition task using 48 naive observers. Both types of smiles were detected in all behavioral states. Lip corner raising with cheek raising (Duchenne smiling) tended to predominate in active (rapid eye movement) sleep, suggesting a potential tie to early constituents of emotion. A significant portion of the typically briefer lip corner raising distinguished by expert coders was not recognized as smiling by the naive observers. These briefer actions may represent a motor phenomenon idiosyncratic to the neonatal period.     

Effects of Maternal Responsiveness on Infant Responsiveness and Behavior in the Still‐Face Task

The effects of maternal responsiveness on infant responsiveness and behavior in the Still‐Face Task were longitudinally examined through infants' first 3 months. Maternal vocal responsiveness and infant vocal and smiling responsiveness significantly increased when infants were 2 months of age. Mothers showed continuity of individual differences in vocal responsiveness from the infants' newborn period. Maternal responsiveness predicted infant responsiveness within and across sessions. Compared with infants with low‐responsive mothers, infants with high‐responsive mothers were more attentive and affectively engaged during the Still‐Face Task from 1 month of age. Infants with high‐responsive mothers discriminated between the task phases with their smiling at 1 month, a month before infants with low‐responsive mothers did so. Infants in both groups discriminated between the phases with their attention and nondistress vocalizations throughout their first 3 months. Results suggest that maternal responsiveness influences infant responsiveness and facilitates infants' engagement and expectations for social interaction.     

Increased Focus on the Mouth Among Infants in the First Year of Life: A Longitudinal Eye‐Tracking Study

This study examines face‐scanning behaviors of infants at 6, 9, and 12 months as they watched videos of a woman describing an object in front of her. The videos were created to vary information in the mouth (speaking vs. smiling) and the eyes (gazing into the camera vs. cueing the infant with head turn or gaze direction to an object being described). Infants tended to divide their attention between the eyes and the mouth, looking less at the eyes with age and more at the mouth than the eyes at 9 and 12 months. Attention to the mouth was greater on speaking trials than on smiling trials at all three ages, and this difference increased between 6 and 9 months. Despite consistent results within subjects, there was considerable variation between subjects. This raises the question of whether a developmental “norm” of face scanning in infancy ought to be pursued. Rather, these data add to emerging evidence suggesting that individual differences in face scanning might reliably predict aspects of later development.     

Onset of Voluntary Communication: Smiling Looks to Mother

Playing infants often direct smiling looks toward social partners. In some cases the smile begins before the look, so it cannot be a response to the sight or behavior of the social partner. In this study we asked whether smiles that anticipate social contact are used by 8‐ to 12‐month‐old infants as voluntary social signals. Eighty infants—20 at each of 8, 9, 10, and 12 months of age—completed 5 tasks. The tasks assessed anticipatory smiling during toy play, means‐end understanding (2 tasks), intentional communication via gesture and vocalizations, and memory for mother's location. Across all ages, anticipatory smiling was strongly predicted by intentional gestural and vocal communication and by means‐end understanding. The findings are discussed in terms of the nature and origins of infants' voluntary communications.     

Infants' Response to Maternal Mirroring in the Still Face and Replay Tasks

Infants' response to maternal mirroring was investigated in 4‐month‐old infants. Mother–infant dyads participated in the still face and replay tasks. Infants were grouped by those whose mothers did and did not mirror their behavior in the interactive phases of the tasks. In the still face task, infants with maternal mirroring showed more attention, smiling, and positive vocalizations across the phases, although both groups of infants demonstrated the still‐face effect with attention and smiling. Infants' social bidding to the mother during the still‐face phase correlated with mothers' mirroring behavior. In the replay task, infants with maternal mirroring demonstrated carryover effects with smiling; infants without maternal mirroring showed no awareness of change in their mothers' behavior. In both the still face and replay tasks, infants with maternal mirroring were more engaged with their mothers. Results suggest that maternal mirroring of infants' behavior affects infants' detection of, and response to, reciprocal interaction.     

The Development of Anticipatory Smiling

When do infants begin to communicate positive affect about physical objects to their social partners? We examined developmental changes in the timing of smiles during episodes of initiating joint attention that involved an infant gazing between an object and a social partner. Twenty‐six typically developing infants were observed at 8, 10, and 12 months during the Early Social‐Communication Scales, a semistructured assessment for eliciting initiating joint attention and related behaviors. The proportion of infant smiling during initiating joint attention episodes did not change with age, but there was a change in the timing of the smiles. The likelihood of infants smiling at an object and then gazing at the experimenter while smiling (anticipatory smiling) increased between 8 and 10 months and remained stable between 10 and 12 months. The increase in the number of infants who smiled at an object and then made eye contact suggests a developing ability to communicate positive affect about an object.     

The Mother–Infant Feeding Relationship Across the First Year and the Development of Feeding Difficulties in Low‐Risk Premature Infants

Although feeding problems are common during infancy and are typically accompanied by relational difficulties, little research observed the mother–infant feeding relationship across the first year as an antecedent to the development of feeding difficulties. We followed 76 low‐risk premature infants and their mothers from the transition to oral feeding in the neonatal period to the end of the first year. Prior to hospital discharge, microlevel patterns of maternal touch and gaze were coded during feeding and nonfeeding interactions, global patterns of maternal adaptation were assessed, and infants' neurobehavioral status was tested. Psychomotor development was evaluated at 4 months. At 1 year, feeding difficulties were determined on the basis of maternal interview and direct observations of feeding interactions. Mothers of infants who exhibited feeding difficulties at 1 year showed less affectionate touch and gaze during nonfeeding interactions and more gaze aversion and lower adaptability during feeding interactions already in the neonatal period. Infants with feeding difficulties demonstrated poorer psychomotor performance at 4 months. Feeding interactions of infants with feeding difficulties at 1 year were characterized by higher maternal intrusiveness, lower infant involvement, and greater infant withdrawal. Less maternal affectionate touch and lower maternal adaptation in the neonatal period, poor infant psychomotor skills, and higher maternal intrusiveness and lower infant involvement at 1 year predicted feeding difficulties. The findings underscore the role of the relational components across the first year in the development of feeding difficulties.     

The Relations between Reactivity at 4 Months and Behavioral Inhibition in the Second Year: Replication across Three Independent Samples

This paper examines the predictive relations between two infant temperamental biases assessed at 4 months and inhibited behavior during the first 2 years of life in three independent samples from two research laboratories. Although each sample used slightly different criteria for classifying infants, the results across samples were consistent. Infants of both genders who displayed high levels of motor activity and distress to unfamiliar events were more inhibited at 14 months of age. By 24 months, there were significant sex differences: Boys identified as high reactive were more inhibited than high reactive girls.     

Looking Behavior and Smiling in Down Syndrome Infants

We studied the relation between direction of gaze and smiling in 15 typically developing infants and 15 infants with Down syndrome. All of them were videotaped during face-to-face interaction with their mothers at home, and while having access to their familiar toys. Results showed that mothers in the two groups behaved in a similar way; that Down syndrome infants looked at their mother's face for longer than typically developing children; and that the relationship between looking and smiling was similar in the two cases and reflected as an increase in the time the infant looked at its mother's face and a decrease in the time the infant looked at toys. It was deduced that Down syndrome infants are capable of distinguishing the differential significance of faces and toys, so that, in the same way as typically developing infants, they direct their affective behavior fundamentally towards the social element, which leads us to consider the affiliative function implied by this expression.     

Twelve months old infants' evaluation of observed comforting behavior using a choice paradigm: The role of animacy cues and self-distress

Comforting is a prosocial behavior that children start to engage in around their second year of life. There is much less known about their ability to evaluate comforting behavior of others. The current study examined whether 12 months old infants, after having watched animated abstract characters comfort or ignore a third party in distress, would show a preference for the comforting character. Using a manual choice paradigm, we found that infants were more likely to choose the comforting character than the ignoring character (Experiment 1). When the characters however lacked human surface features (eyes) infants did not show a preference (Experiment 2). Furthermore, infants self-distress during the watching of the animations did not prevent infants to evaluate the behavior of the observed characters. These findings support the idea of an early presence of “moral sense” in infancy.     

Automated measurement of infant and mother Duchenne facial expressions in the Face-to-Face/Still-Face

Although still-face effects are well-studied, little is known about the degree to which the Face-to-Face/Still-Face (FFSF) is associated with the production of intense affective displays. Duchenne smiling expresses more intense positive affect than non-Duchenne smiling, while Duchenne cry-faces express more intense negative affect than non-Duchenne cry-faces. Forty 4-month-old infants and their mothers completed the FFSF, and key affect-indexing facial Action Units (AUs) were coded by expert Facial Action Coding System coders for the first 30 s of each FFSF episode. Computer vision software, automated facial affect recognition (AFAR), identified AUs for the entire 2-min episodes. Expert coding and AFAR produced similar infant and mother Duchenne and non-Duchenne FFSF effects, highlighting the convergent validity of automated measurement. Substantive AFAR analyses indicated that both infant Duchenne and non-Duchenne smiling declined from the FF to the SF, but only Duchenne smiling increased from the SF to the RE. In similar fashion, the magnitude of mother Duchenne smiling changes over the FFSF were 2–4 times greater than non-Duchenne smiling changes. Duchenne expressions appear to be a sensitive index of intense infant and mother affective valence that are accessible to automated measurement and may be a target for future FFSF research.     

Longitudinal links between maternal factors and infant cognition: Moderation by infant sleep

The current study examined the moderating role of infant sleep in the link between maternal factors (i.e., maternal education, depressive symptoms, sleep disturbance) and infant cognition. Data come from 95 African American parent–child dyads. At 3 months of age, infant sleep was objectively measured using videosomnography and actigraphy, from which measures of sleep regulation and consolidation were calculated. Mothers also self‐reported their level of education, depressive symptoms, and sleep quality. At 6 months of age, infants completed cognitive assessments, including a measure of general cognitive ability and observed attention behavior. Findings revealed that infant sleep quality interacted with maternal education and sleep disturbances to predict cognition. Specifically, the link between maternal education and infants’ attention behavior was significant and positive for infants with better regulated sleep, but not for infants with poorly regulated sleep. Similarly, the link between maternal sleep disturbance and infant cognition depended on infant sleep quality. For infants with poorer sleep consolidation, increased maternal sleep disturbance predicted poorer infant general cognitive ability. For infants with better sleep consolidation, maternal sleep disturbance was positively related to both general cognitive ability and attention behavior. These findings suggest that infant sleep quality moderates the impact of environmental factors on cognitive functioning.     

Biomechanics-based active control of bedding support properties and its influence on sleep

Proper body support plays an import role in the recuperation of our body during sleep. Therefore, this study uses an automatically adapting bedding system that optimises spinal alignment throughout the night by altering the stiffness of eight comfort zones. The aim is to investigate the influence of such a dynamic sleep environment on objective and subjective sleep parameters. The bedding system contains 165 sensors that measure mattress indentation. It also includes eight actuators that control the comfort zones. Based on the measured mattress indentation, body movements and posture changes are detected. Control of spinal alignment is established by fitting personalized human models in the measured indentation. A total of 11 normal sleepers participated in this study. Sleep experiments were performed in a sleep laboratory where subjects slept three nights: a first night for adaptation, a reference night and an active support night (in counterbalanced order). Polysomnographic measurements were recorded during the nights, combined with questionnaires aiming at assessing subjective information. Subjective information on sleep quality, daytime quality and perceived number of awakenings shows significant improvements during the active support (ACS) night. Objective results showed a trend towards increased slow wave sleep. On the other hand, it was noticed that % N1-sleep was significantly increased during ACS night, while % N2-sleep was significantly decreased. No prolonged N1 periods were found during or immediately after steering.     

Maternal Talk About Mental States and the Emergence of Joint Visual Attention

Twenty‐four infants were tested monthly for gaze and point following between 9 and 15 months of age and mother‐infant free play sessions were also conducted at 9, 12, and 15 months (Carpenter, Nagell, & Tomasello, 1998). Using this data set, this study explored relations between maternal talk about mental states during mothers' free play with their infants and the emergence of joint visual attention in infants. Contrary to hypothesis, mothers' comments about their infants' perceptual states significantly declined after their infants began to engage in joint visual attention. Comments about other mental states did not change relative to acquisition of joint visual attention skill. We speculate that after infants begin to reliably follow gaze and points, mothers may switch the focus of their conversation from their infants' visual behavior and experiences to the object of their mutual attention.     

Automated Measurement of Facial Expression in Infant–Mother Interaction: A Pilot Study

Automated facial measurement using computer vision has the potential to objectively document continuous changes in behavior. To examine emotional expression and communication, we used automated measurements to quantify smile strength, eye constriction, and mouth opening in two 6‐month‐old infant‐mother dyads who each engaged in a face‐to‐face interaction. Automated measurements showed high associations with anatomically based manual coding (concurrent validity); measurements of smiling showed high associations with mean ratings of positive emotion made by naive observers (construct validity). For both infants and mothers, smile strength and eye constriction (the Duchenne marker) were correlated over time, creating a continuous index of smile intensity. Infant and mother smile activity exhibited changing (nonstationary) local patterns of association, suggesting the dyadic repair and dissolution of states of affective synchrony. The study provides insights into the potential and limitations of automated measurement of facial action.     

Self‐Awareness in Human and Chimpanzee Infants: What Is Measured and What Is Meant by the Mark and Mirror Test?

The objective study of self‐recognition, with a mirror and a mark applied to the face, was conducted independently by Gallup (1970) for use with chimpanzees and monkeys, and by Amsterdam (1972) for use with infant humans. Comparative psychologists have followed the model (and assumptions) set by Gallup, whereas developmental psychologists have followed a different model (e.g., Lewis & Brooks‐Gunn, 1979). This article explores the assumptions in the definitions and methods of self‐recognition assessments in the 30 years since these initial studies, and charts the divergence between the developmental mark test and the comparative mark test. Two new studies, 1 with infant chimpanzees and 1 with infant humans, illustrate a reconciliation of the 2 approaches. Overt application of the mark, or other procedures related to how the mark is discovered, did not enhance mirror self‐recognition. In contrast, maternal scaffolding appears to enhance performance, perhaps by eliciting well‐rehearsed verbal responses (i.e., naming self). When comparable testing procedures and assessment criteria are used, chimpanzee and human infants perform comparably. A combined developmental comparative approach allows us to suggest that mirror self‐recognition may be based on a specific aspect of mental representation, the cognitive ability to symbolize.     

The Development of Anticipatory Postural Adjustments in Infancy

Efficient voluntary action requires postural adjustments that compensate for potential balance disturbances before they occur. These anticipatory postural adjustments have been widely investigated in adults, but relatively little is known about their development, especially during infancy. This study examined the early development of anticipatory postural activity in support of pulling action while standing. A total of 34 infants between 10 and 17 months were tested. The task required infants to open a cabinet drawer to retrieve toys while a force resisting the pulling action was applied to the drawer. The experiment included between 9 and 13 pulling trials. The force resisting the pull was doubled after the first 4 initial trials and returned again to its original value after another 4 trials. Electromyographic activity from the gastrocnemius and biceps brachii muscles was recorded. The proportion of pulls involving anticipatory activity in the gastrocnemius muscles progressively increased between 10 and 17 months. In addition, infants with considerable experience in opening drawers learned to recruit greater strength of their anticipatory postural adjustments for heavier pulls. Implications for the role of motoric experience in anticipatory postural activity are discussed.     

Preference for Dynamic Human Images and Gaze‐Following Abilities in Preterm Infants at 6 and 12 Months of Age: An Eye‐Tracking Study

Preterm children are reported to be at higher risk of social communication problems such as autism spectrum disorder compared with full‐term infants. Although previous studies have suggested that preference for social stimuli in infancy is a possible indicator of later social communication development, little is known about this relation in preterm infants. We examined the gaze behavior of low‐risk preterm and full‐term infants at 6 and 12 months' corrected ages using two types of eye‐tracking tasks, which measured 1) preference for social stimuli by biological motion and human geometric preference and 2) ability to follow another's gaze direction. We found that preterm (compared with full‐term) infants at both 6 and 12 months of age spent less time looking toward dynamic human images, followed another's gaze less frequently, and looked for a shorter time at an object cued by another. Moreover, we found a positive correlation between looking time toward dynamic human images and frequency of gaze following at 12 months of age in full‐term, but not preterm, infants. We discuss the relation between the atypical patterns of gaze behavior in preterm infants and their higher risk of later social communication problems.     

Probing infants’ sensitivity to pupil size when viewing eyes

Sensitive responding to eye cues plays a key role in human social interactions. Pupil size provides subtle cues regarding a social interaction partner's arousal states. The current study assessed infants’ sensitivity to and preference for differences in pupil size. Specifically, we examined White 14-month-old infants’ pupillary responses when viewing own-race and other-race (Asian) eyes with dilating, constricting, and static medium-sized pupils. Our results show that, independent of race, infants’ pupils dilated more when viewing eyes with dynamically changing (dilating and constricting) pupils than when viewing eyes with non-changing, static, and medium-sized pupils. We also measured infants’ looking preferences, showing that, independent of race, infants preferentially attended to eyes with dilated pupils. Moreover, our results show that infants orient more quickly to pupillary changes in own-race eyes than in other-race eyes. These findings demonstrate that infants detect, but do not mimic, changes in pupil size in others and show a preference for eyes with dilated pupils.