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While early life sets the stage for later learning, comparatively less is known about newborns' cognition than that of older infants. A striking example is the lack of consensus regarding the extent to which newborns spontaneously mimic gestures, and whether such behavior drives bonding and learning. Despite the theoretical importance of these questions, practical challenges limit researchers' ability to engage newborns in behavioral research. Webcam‐based, asynchronous online studies have expanded developmental science's capacity to reach older infants. However, such scalable and replicable methods have yet to be deployed with younger infants. Taking a commonly‐used neonatal mimicry paradigm as a test case, we assessed the feasibility of leveraging an open‐source online platform (Children Helping Science) for asynchronous research with 0–6‐week‐olds and their caregivers. Caregivers modeled face movements to their 4–45 days‐old infants (N = 29, N = 17 included) while webcams filmed their infants' responses; 13 dyads participated more than once (72 included test videos). Preliminary evidence suggested that infants do not mimic caregivers' tongue protrusions (Bayes Factor ∼ ⅓). Data on the mimicry of caregivers' mouth openings was inconclusive (⅓ < BF < 3). Additional analyses identified a target sample size for future studies. Finally, we asked whether caregivers perceived their newborns' behavior as imitative. Caregivers' perceptions of mimicry reflected infants' behaviors but did not align with an often‐used metric of mimicry (“imitators”). These results demonstrate the feasibility of asynchronous online behavioral studies with newborns and provide a foundation for future research on neonatal mimicry of caregivers. 

Growing empirical evidence from the past quarter century reveals surprising sociality in newborns—infants in the first 28 postnatal days—including their ability to elicit and sustain contingent interactions with mutual gaze, social smiling, and sensitively timed, speech-like vocalizations. Newborns seem to have communicative expectations and behave as if they predict others’ goal-directed actions. Despite these discoveries, I review key barriers to progress in newborn developmental science. First, newborn social behavior research has almost exclusively focused on “average” development—based primarily on White, wealthy, English-speaking, Western, populations—treating interindividual differences as noise rather than meaningful, variability. Focusing almost exclusively on averages, especially with small sample sizes, ignores interindividual differences and hinders discoveries. Second, there are few studies of newborn sociality beyond the first postnatal week. In part, this gap in our understanding may be due to, and a consequence of, the mischaracterizations of newborns’ behaviors as passive, limited, disorganized, and low-level reflexes that are subcortically driven. Finally, researchers often assume that newborns’ behaviors are largely independent of experience. To the contrary, newborns’ need for nearly continuous social contact provides them with rich social learning opportunities, which have been shown to have lasting impacts on their development. Given the uniqueness and plasticity of this period, and their high vulnerability, developmental scientists are doing newborns a disservice by neglecting to characterize their social repertoires within and across diverse populations. Awareness of newborns’ social capacities will facilitate a more objective, accurate view of their social potential. 

Given the foundational nature of infant visual attention and potential cascading effects on later development, studies of individual variability in developmental trajectories in a normative sample are needed. We longitudinally tested newborns (N = 77) at 1–2 and 3–4 weeks, then again at 2, 4, 6, 8 and 14 months of age, assessing individual differences in their attention. Newborns viewed live stimuli (facial gesturing, rotating disk), one at a time, for 3 min each. Older infants viewed a 10‐s side‐by‐side social–nonsocial video (people talking, rotating disk). We found short‐term developmental stability of interindividual differences in infants’ overall, social, and nonsocial attention, within the newborn period (1–4 weeks), and within the later infancy period (2–14 months). Additionally, we found that overall attention, but not social and nonsocial attention, was developmentally stable long term (newborn through 14 months). This novel finding that newborn overall attention predicts later overall attention through the first year suggests a robust individual difference. This study is a first step toward developing individual difference measures of social and nonsocial attention. Future studies need to understand why newborns vary in their attention and to identify the potential impact of this variability on later social and cognitive development. 

Pareidolic faces—illusory faces in objects—offer a unique context for studying biases in the development of facial processing because they are visually diverse (e.g., color, shape) while lacking key elements of real faces (e.g., race, species). In an online study, 7- and 8-year-old children (n = 32) and adults (n = 32) categorized happy and angry expressions in human and pareidolic face images. We found that children have a robust, adult-like happy face advantage for human and pareidolic faces, reflected in speed and accuracy. These results suggest that the happy face advantage is not unique to human faces, supporting the hypothesis that humans employ comparable face templates for processing pareidolic and human faces. Our findings add to a growing list of other processing similarities between human and pareidolic faces and suggest that children may likewise show these similarities. 

Infants’ nonverbal expressions—a broad smile or a sharp cry—are powerful at eliciting reactions. Although parents’ reactions to their own infants’ expressions are relatively well understood, here we studied whether adults more generally exhibit behavioral and physiological reactions tounfamiliarinfants producing various expressions. We recruited U.S. emerging adults (N = 84) prior to parenthood, 18–25 years old, 68% women, ethnically (20% Hispanic/Latino) and racially (7% Asian, 13% Black, 1% Middle Eastern, 70% White, 8% multiracial) diverse. They observed four 80‐s audio–video clips of unfamiliar 2‐ to 6‐month‐olds crying, smiling, yawning, and sitting calmly (emotionally neutral control). Each compilation video depicted 9 different infants (36 clips total). We found adults mirrored behaviorally and physiologically: more positive facial expressions to infants smiling, and more negative facial expressions and pupil dilation—indicating increases in arousal—to infants crying. Adults also yawned more and had more pupil dilation when observing infants yawning. Together, these findings suggest that even nonparent emerging adults are highly sensitive to unfamiliar infants’ expressions, which they naturally “catch” (i.e., behaviorally and physiologically mirror), even without instructions. Such sensitivity may have—over the course of humans’ evolutionary history—been selected for, to facilitate adults’ processing of preverbal infants’ expressions to meet their needs. 

Oxytocin is a neuropeptide positively associated with prosociality in adults. Here, we studied whether infants' salivary oxytocin can be reliably measured, is developmentally stable, and is linked to social behavior. We longitudinally collected saliva from 62 U.S. infants (44 % female, 56 % Hispanic/Latino, 24 % Black, 18 % non-Hispanic White, 11 % multiracial) at 4, 8, and 14 months of age and offline-video-coded the valence of their facial affect in response to a video of a smiling woman. We also captured infants' affective reactions in terms of excitement/joyfulness during a live, structured interaction with a singing woman in the Early Social Communication Scales at 14 months. We detected stable individual differences in infants' oxytocin levels over time (over minutes and months) and in infants' positive affect over months and across contexts (video-based and in live interactions). We detected no statistically significant changes in oxytocin levels between 4 and 8 months but found an increase from 8 to 14 months. Infants with higher oxytocin levels showed more positive facial affect to a smiling person video at 4 months; however, this association disappeared at 8 months, and reversed at 14 months (i.e., higher oxytocin was associated with less positive facial affect). Infant salivary oxytocin may be a reliable physiological measure of individual differences related to socio-emotional development. 

Objective. Maternal stress is a psychological response to the demands of motherhood. A high level of maternal stress is a risk factor for maternal mental health problems, including depression and anxiety, as well as adverse infant socioemotional and cognitive outcomes. Yet, levels of maternal stress (i.e., levels of stress related to parenting) among low-risk samples are rarely studied longitudinally, particularly in the first year after birth. Design. We measured maternal stress in an ethnically diverse sample of low-risk, healthy U.S. mothers of healthy infants (N = 143) living in South Florida across six time points between 2 weeks and 14 months postpartum using the Parenting Stress Index-Short Form, capturing stress related to the mother, mother-infant interactions, and the infant. Results. Maternal distress increased as infants aged for mothers with more than one child, but not for first-time mothers whose distress levels remained low and stable across this period. Stress related to mother-infant dysfunctional interactions lessened over the first 8 months. Mothers’ stress about their infants’ difficulties decreased from 2 weeks to 6 months, and subsequently increased from 6 to 14 months. Conclusions. Our findings suggest that maternal stress is dynamic across the first year after birth. The current study adds to our understanding of typical developmental patterns in early motherhood and identifies potential domains and time points as targets for future interventions. 

This study examined the development of children's avoidance and recognition of sickness using face photos from people with natural, acute, contagious illness. In a U.S. sample of fifty‐seven 4‐ to 5‐year‐olds (46% male, 70% White), fifty‐two 8‐ to 9‐year‐olds (26% male, 62% White), and 51 adults (59% male, 61% White), children and adults avoided and recognized sick faces (ds ranged from 0.38 to 2.26). Both avoidance and recognition improved with age. Interestingly, 4‐ to 5‐year‐olds' avoidance of sick faces positively correlated with their recognition, suggesting stable individual differences in these emerging skills. Together, these findings are consistent with a hypothesized immature but functioning and flexible behavioral immune system emerging early in development. Characterizing children's sickness perception may help design interventions to improve health. 

Infants vary in their ability to follow others’ gazes, but it is unclear how these individual differences emerge. We tested whether social motivation levels in early infancy predict later gaze following skills. We longitudinally tracked infants’ (N = 82) gazes and pupil dilation while they observed videos of a woman looking into the camera simulating eye contact (i.e., mutual gaze) and then gazing toward one of two objects, at 2, 4, 6, 8, and 14 months of age. To improve measurement validity, we used confirmatory factor analysis to combine multiple observed measures to index the underlying constructs of social motivation and gaze following. Infants’ social motivation—indexed by their speed of social orienting, duration of mutual gaze, and degree of pupil dilation during mutual gaze—was developmentally stable and positively predicted the development of gaze following—indexed by their proportion of time looking to the target object, first object look difference scores, and first face‐to‐object saccade difference scores—from 6 to 14 months of age. These findings suggest that infants’ social motivation likely plays a role in the development of gaze following and highlight the use of a multi‐measure approach to improve measurement sensitivity and validity in infancy research.