Physiological and Emotional Reactivity to Learning and Frustration

This study examined the behavioral (arm, facial) and autonomic (heart rate, respiratory sinus arrhythmia [RSA], and adrenocortical axis) reactivity of 56 4‐month‐old infants in response to contingency learning and extinction‐induced frustration. During learning, infants displayed increases in operant arm response and positive emotional expressions. Changes in average RSA(V_NA) paralleled the observed changes in facial expressions in general and maintained an inverse relation with heart rate throughout most of the session. When frustrated by extinction, infants displayed increases in negative expressions, heart rate, and a brief increase in RSA(V_NA) followed by a significant decrease. No significant changes were observed for Cortisol. These behavioral and facial responses are consistent with earlier work. The physiological changes, along with the facial expressions and instrumental responses, indicate that the autonomic nervous system functions as a coordinated affect system by 4 months of age.     

Olfactory Familiarization and Discrimination in Preterm and Full‐Term Newborns

The purpose of this study was to observe olfactory detection and discrimination in preterm and full‐term newborns. Infants were familiarized for 10 trials with either vanillin or anethole. On each trial, a cotton swab perfumed with one of the odors was slowly moved in front of the baby's nose for 10 sec. For half of the preterm and full‐term infants, a new odor was presented after the last familiarization trial (experimental groups). For the other half, the same odor as during familiarization was presented (control groups). Facial and head movements for both populations and heart rates for preterm infants were recorded before, during, and after odor presentation. Preterm infants reacted to the scents by increasing facial actions and heart rate but not head movements. Full‐term infants increased facial and head movements. Neither population showed a clear behavioral habituation pattern, but full‐term newborns had a significantly reduced facial reactivity on the last familiarization trial compared to preterm infants. Preterm newborns did, however, show cardiac habituation on the last familiarization trial. Preterm and full‐term infants presented with a new odor after familiarization increased responding compared to infants presented with the same odor, indicating their ability to discriminate between 2 odors. Infants' reactivity and discrimination to odors indicate preterm and full‐term newborns' ability to be attuned to their olfactory environment.     

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.     

Physiological Reactivity to Infant Crying and Observed Maternal Sensitivity

Relations between maternal sensitivity and physiological reactivity to infant crying were examined using measures of heart rate (HR) and respiratory sinus arrhythmia (RSA) in 49 mothers of second‐born infants. Using the Ainsworth Sensitivity Scale, an independent assessment of maternal sensitivity was made during maternal free play and bathing of their infants. Physiological reactivity was measured while mothers listened to three blocks of infant cry sounds in a standard cry paradigm. Mothers scoring high on sensitivity were compared to less sensitive mothers on both their physiological reactivity to the presented crying sounds and their physiological mean‐level differences. Significant interaction effects were found for both HR and RSA. Highly sensitive mothers showed a larger increase in HR and stronger RSA withdrawal in response to the first block of cry sounds compared to less sensitive mothers. Main effects showed that highly sensitive mothers had lower mean overall HR, and higher mean RSA levels across all three blocks of crying sounds compared to less sensitive mothers. RSA withdrawal and accompanying HR increases are discussed from a polyvagal perspective as indicative of a better capability in responding to infant signals of negative affect.     

Contrasts in Infant Classical Eyeblink Conditioning as a Function of Premature Birth

The impact of premature birth on associative learning was evaluated using simple delay eyeblink conditioning in which a tone conditional stimulus was paired with an air puff unconditional stimulus. Fourteen preterm (28–31 weeks gestation) and 11 full‐term infants completed at least 3 conditioning sessions, 1 week apart, at 5 months of age (corrected age). Preterm and full‐term groups demonstrated associative learning, as confirmed by comparison with an unpaired control group. Preterm infants, however, exhibited more variability in their learning rates. The majority of full‐term infants and half the preterm infants exhibited rapid acquisition and gradual extinction of conditional responding. A greater proportion of preterm than full‐term infants failed to acquire conditional responding within 2 training sessions. Differences in associative learning rates were not the result of differences in arousal or attentional processes. Diversity in acquisition rates exposed an increased risk for disrupted infant learning due to premature birth.     

Temperamental Susceptibility to Parenting among Preterm and Full‐Term Infants in Early Cognitive Development

The current study examined the interaction between premature birth, temperamental reactivity, and parenting in early cognitive development. Participants were 142 infants (80 preterm; 62 full term) and their parents. Parent–child interactions (maternal, paternal, and co‐parental) were observed at age 6 months to assess parental structuring behaviors. Additionally, both parents reported on infants' temperamental reactivity. At 12 months of age, infants' cognitive abilities were assessed. Consistent with the diathesis–stress model, preterm infants had lower cognitive outcomes than full‐term infants when exposed to low levels of co‐parental structuring, but functioned similarly when exposed to high levels of co‐parental structuring. However, temperamental reactivity moderated this effect: Infants who carried one susceptibility factor (i.e., premature birth or reactive temperament) were similarly affected by co‐parental structuring, whereas infants who carried two or no susceptibility factors were not. Furthermore, consistent with the differential susceptibility hypothesis, infants with highly reactive temperaments had lower cognitive functioning when exposed to low maternal structuring, but higher cognitive functioning when exposed to high maternal structuring compared to infants with lower reactivity. Results from this study highlight the importance of considering both temperamental reactivity and quality of parenting in understanding preterm infants' early cognitive vulnerability.     

Individual Differences in Infants' Recognition of Briefly Presented Visual Stimuli

Infants' recognition memory has been shown to be related to individual differences in look duration and level of heart period variability. This study examined the effect of individual differences in these 2 measures on infants' recognition of briefly presented visual stimuli using a paired‐comparison recognition‐memory paradigm. A sample of 35 full‐term infants was studied longitudinally at 14, 20, and 26 weeks of age. Recognition memory for briefly presented stimuli was tested in 6 experimental conditions, with delays corresponding to different heart‐rate‐defined phases of attention. The 20‐and 26‐week‐old infants, and infants with high levels of heart period variability, generally showed more evidence of recognition memory for briefly presented visual stimuli. Greater evidence of recognition memory was observed when stimuli were presented during sustained attention. Infants with more mature baseline physiological responses show greater evidence of recognition memory, and stimulus and procedural factors may be more important for the study of individual differences in infant visual attention than has previously been suggested.     

Coregulation and the Quality of the Relationship in Full‐Term and Very Low‐Birthweight Preterm Infant‐Mother Dyads During Face‐To‐Face Interactions

Interactions with parents build the foundation for infants' social–emotional development. This study investigated coregulation of the interaction and quality of relationship between mothers and their 6‐month‐old full‐term (n = 43) and very low‐birthweight/preterm (VLBW/preterm; n = 44; ages corrected for prematurity) infants. The objectives were to examine (1) how coregulation changed following a perturbed interaction, (2) how coregulation differed between full‐term and VLBW/preterm infant–mother dyads, and (3) the association between coregulation and relationship quality. Coregulation was coded using the Revised Relational Coding System (Fogel et al., 2003). Quality of the relationship was measured using the Emotional Availability scales (Biringen et al., 2014; Carter et al., 1998). Dyads participated in the Still‐Face (SF) procedure (Tronick et al., 1978) consisting of two natural and one SF period where mothers assumed a neutral expression, refraining from interacting with their infants. Following the SF period, dyads engaged in more symmetrical and more disruptive patterns of coregulation. While full‐term dyads engaged in more sequential‐symmetrical, VLBW/preterm dyads engaged in more resonant‐symmetrical coregulation. These results suggest that VLBW/preterm dyads may show more emotional reactivity in their interactions than full‐term dyads; however, in both groups infant responsiveness and parenting stress influenced the types of coregulation exhibited.     

Longitudinal assessment of social attention in preterm and term infants: Its relation to social communication and language outcome

Preterm birth has been reported to be associated with an increased risk of social communication and language problems. Recently, we found that preterm infants showed atypical patterns of social attention compared with term infants. However, it is still unknown how social attention develops and whether the individual differences are associated with developmental outcomes for social communication and language in preterm infants. The social attention of preterm and term infants at 6, 12, and 18 months was investigated using two types of social attention tasks (human-geometric preference task and gaze-following task). The Modified Checklist for Autism in Toddlers (M-CHAT) and the MacArthur Communicative Development Inventory adapted for Japanese were measured at 18 months. We found that compared with term infants, preterm infants spent less time looking toward dynamic human images and followed another's gaze directions less frequently through 6, 12, and 18 months. Moreover, hierarchical multiple regression analysis revealed that less preference for dynamic human images and gaze-following abilities was associated with high M-CHAT and low language scores in preterm and term infants, respectively. These findings suggest that birth status affects development of social attention through 18 months and individual differences in social attention reflect differences in social communication and language outcomes.     

Development of Tactile Responses in Human Preterm and Full‐Term Infants From 30 to 40 Weeks Postconceptional Age

Maturation of tactile sensitivity prior to term was examined in 36 preterm and 13 full‐term infants using a fixed‐trial, habituation procedure. Each infant was presented with a series of 8 habituation (arm stroke), 2 novel (arm lift), and 2 recovery (arm stroke) stimulus trials while heart rate and body movements were recorded. Maturation was observed with a gradual increase in the magnitude of the stimulus‐elicited cardiac acceleration and cardiac‐movement coupling from 30 to 40 weeks postconceptional age. The majority of infants displayed habituation—an excitatory response (heart rate acceleration and body movement)—to the initial presentation of a tactile stimulus, response decline with repeated stimulations, and renewed response to a novel stimulus. A substantial number of infants (40%) failed to respond initially to the tactile stimulus, increased responding over several stimulus presentations, and failed to discriminate the presentation of a novel stimulus. We speculate that these differences in response patterns observed over all ages represent individual difference in the perception of stimulus intensity.     

Effects of Contingent Reinforcement of Actions on Infants' Object‐Directed Reaching

The role of contingency learning was examined in 3‐month‐old infants' reaching movements. Infants in the experimental group experienced 9 min of active training during which they could move their arms in a reach‐like fashion to pull and move a mobile. Infants in the control group experienced 9 min of passive training during which they watched a mobile move. Prior to (pre‐training) and following the mobile experience (post‐training), infants in both conditions were given an opportunity to interact with a rattle placed within and out of their reach. Compared with infants in the control condition, infants in the experimental condition produced reach‐like movements more frequently during the mobile experience; they also showed a greater increase in reaching attempts from pre‐ to post‐training assessments with the rattle. These findings show that reinforcement of arm extensions and retractions increases the frequency of infants' reaching behaviors. This result suggests that the reinforcement of components of infants' behaviors may contribute to the successful assembly of these behaviors. This process could help keep infants engaged during the lengthy transition from prereaching to independent reaching.     

Electrophysiological Brain Responses of Six‐Month‐Old Low Risk Premature Infants

This study sought to examine the electrophysiological correlates of visual perceptual priming in a sample of low risk preterm infants. We compared the ERP data of 20 healthy preterm infants at the age of 6 months (corrected age: 4 months) to those of 20 six‐month‐old and 20 four‐month‐old full term infants. The comparison groups represented the preterm infants' chronological and corrected ages respectively. The results showed that the brain responses of the preterm infants at the age of 6 months, specifically the topography and the latency of the Nc component, are more similar to those of their corrected age peers than to those of the chronological age controls.     

Early Segmentation Abilities in Preterm Infants

Infants born preterm have higher risks of developing linguistic deficits. Considering that the ability to segment words from fluent speech is crucial for lexical acquisition, Experiment 1 tested the ability of healthy extremely‐to‐late preterm infants to segment monosyllabic words at 6 months of postnatal age. Results establish basic segmentation skills in these infants. While we failed to find an effect of the degree of prematurity, this issue will need further exploration. Future studies will also have to specify the scope of these early segmentation skills, both in terms of the types of words segmented, the cues used to do so, and in terms of possible differences in performance between subgroups of preterm infants (e.g., based on gestational age or medical risks). Lastly, given that the preterm infants tested had a mean maturational age of 4 months, Experiment 2 explored monosyllabic segmentation in full‐term 4‐month olds. Infants succeeded at the task, providing the earliest developmental evidence of word segmentation in full‐term infants. These findings better specify the early trajectory of segmentation abilities in both full‐term and healthy, low‐risk preterm infants and support the proposal that prematurity might have a differential effect on the early acquisition of various linguistic levels.     

Gaze Behaviors of Preterm and Full‐Term Infants in Nonsocial and Social Contexts of Increasing Dynamics: Visual Recognition,Attention Regulation,and Gaze Synchrony

Although research has demonstrated poor visual skills in premature infants, few studies assessed infants’ gaze behaviors across several domains of functioning in a single study. Thirty premature and 30 full‐term 3‐month‐old infants were tested in three social and nonsocial tasks of increasing complexity and their gaze behavior was micro‐coded. In a one‐trial version of the visual recognition paradigm, where novel stimuli were paired with familiar stimuli, preterm infants showed longer first looks to novel stimuli. In the behavior response paradigm, which presented infants with 17 stimuli of increasing complexity in a predetermined “on‐off” sequence, premature infants tended to look away from toys more during presentation. Finally, during mother–infant face‐to‐face interaction, the most dynamic interpersonal context, preterm infants and their mothers displayed short, frequent episodes of gaze synchrony, and lag‐sequential analysis indicated that both mother and infant broke moments of mutual gaze within 2 sec of its initiation. The propotion of look away during the behavior response paradigm was related to lower gaze synchrony and more gaze breaks during mother–infant interactions. Results are discussed in terms of the unique and adaptive gaze patterns typical of low‐risk premature infants.     

What Habituates in Infant Visual Habituation? A Psychophysiological Analysis

Despite the use of visual habituation over the past half century, relatively little is known about its underlying processes. We analyzed heart rate (HR) taken simultaneous with looking during infant‐controlled habituation sessions collected longitudinally at 4, 6, and 8 months of age with the goal of examining how HR and HR‐defined phases of attention change across habituation. There were four major findings. First, the depth and topography of decelerations and proportion of sustained attention (SA) did not vary across habituation at any age, which suggested (in contrast to the tenets of comparator theory) the persistence of substantial cognitive activity at the end of visual habituation. Second, attention termination (AT) robustly declined across trials, suggesting that, contrary to prior thinking, AT might be a sensitive indicant of visual learning. Third, infants at all ages showed an HR increase (startle) to stimulus onset on the first trial, the magnitude of which was associated with subsequent delayed HR deceleration and less SA; thus, stimulus events affect processing during trials. Finally, mean overall HR reliably increased across trials for all ages. This last finding implies the need to distinguish between “phasic” HR changes (e.g., decelerations during looks) and longer term “tonic” HR changes (mean increases across trials) during habituation, and raises the question of what processes the tonic increases might reflect within the habituation paradigm.     

Infants born full term and preterm increase the height of anti-gravity leg movements during a kick-activated mobile task using a scaffolded task environment

Prior research supports that infants born very preterm (PT), compared with full term (FT), have early differences in rate of learning and motor control that may hinder their ability to learn challenging motor tasks. Four-month-old infants born FT (n = 18) and PT (n = 18) participated in an infant kick-activated mobile task that was scaffolded to motivate progressively higher kicks. We found the FT group learned the association between their leg movements and mobile activation on the second day, but the PT group learned the association on the third day. Both groups of infants increased the height of their kicks on the day they learned the task, compared with their spontaneous kicking height. These findings suggest that infants born PT have the ability to learn challenging motor tasks, such as kicking high, when participating in a task environment that uses scaffolding.     

Predicting Individual Differences in Recall by Infants Born Preterm and Full Term

A heterogeneous sample of infants with preterm histories and infants born full term participated in a study of declarative memory and rate of encoding, as measured in an imitation task and an examining task, respectively. Here we report the comparisons of the performances of infants born very preterm (27–34 weeks gestation) and moderately preterm (35–37 weeks gestation) to infants born full term (38–41 weeks gestation) and tested at 12 months corrected age (from due date). Lower levels of recall were seen among the infants born very preterm. Rate of encoding, weeks gestation, and score on the Mental Development Index (MDI) of the Bayley Scales of Infant Development were tested as possible sources of individual differences in recall. Rate of encoding and MDI predicted delayed ordered recall. Implications for early detection of cognitive difficulties in children with preterm histories are discussed.     

Exploring the Emergence of Side Biases and Familiarity–Novelty Preferences from the Real‐Time Dynamics of Infant Looking

This study examined how look dynamics contribute to infants’ emerging novelty preferences. Time‐series analyses were used to study the temporal nature of looking displayed by 3‐ to 5‐month‐old infants during a serial paired‐comparison task. Evidence was found only for short‐term stability: Novelty preferences and side biases were not stable from one visit to the next, but looking was consistent from one moment to the next producing stability within trials and temporarily across trials leading to the formation of behavioral runs. Persistence in looking left or right across multiple trials did not change from one visit to the next, but persistence in looking at familiar stimuli declined with age. By Visit 3, familiarity runs occurred less often than did novelty runs. Frequent but highly variable runs, including surprisingly late familiarity preferences, suggest that overall side biases and novelty preferences found during visual preference tasks are emergent phenomena affected by moment‐to‐moment changes in looking.     

Very Preterm and Full‐Term Infants’ Response to Socio‐Emotional Stress: The Role of Postnatal Maternal Bonding

Very preterm (VPT) infants are at risk for altered socio‐emotional stress regulation, even in the absence of perinatal complications. Moreover, becoming a mother of a VPT infant is a traumatic event, which might affect the establishment of a bonding relationship toward the infant during the postnatal period. The main aim of the present study was to assess the association between maternal postnatal bonding and socio‐emotional stress response in 3‐month‐old VPT infants, compared to full‐term (FT) controls. Thirty‐three VPT and 28 FT infant‐mother dyads underwent the maternal Face‐to‐Face Still‐Face (FFSF) procedure to assess socio‐emotional stress regulation. Maternal postnatal bonding was measured through the Maternal Post‐Natal Attachment Scale (MPAS), which includes three scales: Quality of attachment, Absence of hostility, and Pleasure in interaction. The VPT infants exhibited less self‐directed and other‐directed regulatory behaviors during the Still‐Face episode. Mothers of VPT infants reported lower Quality of attachment compared to FT counterparts. Importantly, higher levels of Quality of attachment were associated with more other‐directed behaviors during the Still‐Face episode in FT dyads, whereas this was not observed in VPT dyads. In conclusion, VPT infants might be exposed to a double‐risk condition for socio‐emotional development, encompassing both difficulties in stress response and the exposure to a less‐than‐optimal maternal bonding.     

Behavior of Mothers and Infants With and Without Down Syndrome During the Still‐Face Procedure

There has been limited study of how the constitutional characteristics of infants with Down syndrome (DS) influence the patterning of their relations with caregivers. To assess natural and perturbed interactions between infants with DS and their mothers, we tested ten 6‐month‐old infants with DS and 20 typically developing (TD) 4‐month‐old of similar mental age. Participants were videotaped with their mothers in a natural face‐to‐face interaction, a brief period when the mothers adopted a still‐face, and a subsequent reengagement phase. There was little to distinguish the infants in the initial phase of natural interaction, but the mothers of infants with DS were more likely to show assertive warmth, and unlike in the case of mothers of TD infants, high maternal directiveness tended to be associated with lower levels of infant looking and lack of fussing. During the still‐face episode, infants of both groups showed reduced looking and smiling, although infants with DS tended to show lower levels of fussing and fewer in this group showed fussing in the reengagement phase. Therefore DS infants were somewhat similar to TD infants of comparable mental age in being responsive to the still‐face procedure, but showed indications of group differences in intense emotional reactivity.