Maximizing valid eye-tracking data in human and macaque infants by optimizing calibration and adjusting areas of interest

Remote eye tracking with automated corneal reflection provides insights into the emergence and development of cognitive, social, and emotional functions in human infants and non-human primates. However, because most eye-tracking systems were designed for use in human adults, the accuracy of eye-tracking data collected in other populations is unclear, as are potential approaches to minimize measurement error. For instance, data quality may differ across species or ages, which are necessary considerations for comparative and developmental studies. Here we examined how the calibration method and adjustments to areas of interest (AOIs) of the Tobii TX300 changed the mapping of fixations to AOIs in a cross-species longitudinal study. We tested humans (N = 119) at 2, 4, 6, 8, and 14 months of age and macaques (Macaca mulatta; N = 21) at 2 weeks, 3 weeks, and 6 months of age. In all groups, we found improvement in the proportion of AOI hits detected as the number of successful calibration points increased, suggesting calibration approaches with more points may be advantageous. Spatially enlarging and temporally prolonging AOIs increased the number of fixation-AOI mappings, suggesting improvements in capturing infants' gaze behaviors; however, these benefits varied across age groups and species, suggesting different parameters may be ideal, depending on the population studied. In sum, to maximize usable sessions and minimize measurement error, eye-tracking data collection and extraction approaches may need adjustments for the age groups and species studied. Doing so may make it easier to standardize and replicate eye-tracking research findings.

Infection detection in faces: Children's development of pathogen avoidance

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.

Validation of an open source, remote web-based eye-tracking method (WebGazer) for research in early childhood

Measuring eye movements remotely via the participant's webcam promises to be an attractive methodological addition to in-person eye-tracking in the lab. However, there is a lack of systematic research comparing remote web-based eye-tracking with in-lab eye-tracking in young children. We report a multi-lab study that compared these two measures in an anticipatory looking task with toddlers using WebGazer.js and jsPsych. Results of our remotely tested sample of 18-27-month-old toddlers (N = 125) revealed that web-based eye-tracking successfully captured goal-based action predictions, although the proportion of the goal-directed anticipatory looking was lower compared to the in-lab sample (N = 70). As expected, attrition rate was substantially higher in the web-based (42%) than the in-lab sample (10%). Excluding trials based on visual inspection of the match of time-locked gaze coordinates and the participant's webcam video overlayed on the stimuli was an important preprocessing step to reduce noise in the data. We discuss the use of this remote web-based method in comparison with other current methodological innovations. Our study demonstrates that remote web-based eye-tracking can be a useful tool for testing toddlers, facilitating recruitment of larger and more diverse samples; a caveat to consider is the larger drop-out rate.

Elevated risk for developmental disabilities in children with congenital heart defects

BACKGROUND

This study examined risk for developmental disabilities in preschool-aged children with a congenital heart defect (CHD) at the population level.

METHODS

Statewide birth, birth defects, and preschool developmental disability records were integrated. The final sample included 1,966,585 children (51.0% male). Children were grouped by type(s) of CHD: critical CHD, noncritical CHD, atrial septal defect, or no major birth defects (groups were mutually exclusive).

RESULTS

Children with a CHD (any type) were at increased risk for developmental disability (any type) (RR 2.08, 95% CI 2.03-2.14, P < .001). Children in the critical CHD, noncritical CHD, and atrial septal defect groups were at increased risk for developmental delay, intellectual disability, language impairment, other health impairment, and any disability. Children in the atrial septal defect group were at increased risk for autism spectrum disorder and speech impairment. For all CHD groups, risk was greatest for other health impairment and intellectual disability.

CONCLUSIONS

Increased risk for developmental disabilities was identified for children with less severe CHDs as well as for children with more severe (critical) CHDs. All children with CHDs should be closely monitored so that appropriate interventions can be initiated as early as possible to maximize learning outcomes.

Social motivation predicts gaze following between 6 and 14 months

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.

Sensing echoes: temporal misalignment in auditory brainstem responses as the earliest marker of neurodevelopmental derailment

Neurodevelopmental disorders are on the rise worldwide, with diagnoses that detect derailment from typical milestones by 3 to 4.5 years of age. By then, the circuitry in the brain has already reached some level of maturation that inevitably takes neurodevelopment through a different course. There is a critical need then to develop analytical methods that detect problems much earlier and identify targets for treatment. We integrate data from multiple sources, including neonatal auditory brainstem responses (ABR), clinical criteria detecting autism years later in those neonates, and similar ABR information for young infants and children who also received a diagnosis of autism spectrum disorders, to produce the earliest known digital screening biomarker to flag neurodevelopmental derailment in neonates. This work also defines concrete targets for treatment and offers a new statistical approach to aid in guiding a personalized course of maturation in line with the highly nonlinear, accelerated neurodevelopmental rates of change in early infancy.

Infant temperamental fear, pupil dilation, and gaze aversion from smiling strangers

In childhood, higher levels of temperamental fear-an early-emerging proclivity to distress in the face of novelty-are associated with lower social responsivity and greater social anxiety. While the early emergence of temperamental fear in infancy is poorly understood, it is theorized to be driven by individual differences in reactivity and self-regulation to novel stimuli. The current study used eye tracking to capture infants' (N = 124) reactions to a video of a smiling stranger-a common social encounter-including infant gaze aversions from the stranger's face (indexing arousal regulation) and pupil dilation (indexing physiological reactivity), longitudinally at 2, 4, 6, and 8 months of age. Multilevel mixed-effects models indicated that more fearful infants took more time to look away from a smiling stranger's face than less fearful infants, suggesting that high-fear infants may have slower arousal regulation. At 2 and 4 months, more fearful infants also exhibited greater and faster pupil dilation before gaze aversions, consistent with greater physiological reactivity. Together, these findings suggest that individual differences in infants' gaze aversions and pupil dilation can index the development of fearful temperament in early infancy, facilitating the identification of, and interventions for, risk factors to social disruptions.

A Prediction Model for Positive Infant Meconium and Urine Drug Tests

OBJECTIVE

This study aimed to determine the factors associated with positive infant drug screen and create a shortened screen and a prediction model.

STUDY DESIGN

This is a retrospective cohort study of all infants who were tested for drugs of abuse from May 2012 through May 2014. The primary outcome was positive infant urine or meconium drug test. Multivariable logistic regression was used to identify independent risk factors. A combined screen was created, and test characteristics were analyzed.

RESULTS

Among the 3,861 live births, a total of 804 infants underwent drug tests. Variables associated with having a positive infant test were (1) positive maternal urine test, (2) substance use during pregnancy, (3) ≤ one prenatal visit, and (4) remote substance abuse; each p-value was less than 0.0001. A model with an indicator for having at least one of these four predictors had a sensitivity of 94% and a specificity of 69%. Application of this screen to our population would have decreased drug testing by 57%. No infants had a positive urine drug test when their mother's urine drug test was negative.

CONCLUSION

This simplified screen can guide clinical decision making for determining which infants should undergo drug testing. Infant urine drug tests may not be needed when a maternal drug test result is negative.

KEY POINTS

· Many common drug screening criteria are not predictive.. · Four criteria predicted positive infant drug tests.. · No infant urine drug test is needed if the mother tests negative..

Breastfeeding Advocacy: A Look into the Gap Between Breastfeeding Support Guidelines and Personal Breastfeeding Experiences of Faculty Physicians

Objectives: Despite increased lactation support for mothers over the past few decades, physician mothers still face considerable challenges to achieving their breastfeeding goals. Disparities in breastfeeding exist between physician and nonphysician mothers in the United States. To formulate an effective advocacy agenda for this population, we surveyed faculty physician mothers about their breastfeeding experiences. We hypothesized that identifying frequent, modifiable barriers to breastfeeding could generate ideas for improved lactation support for female physicians. Study Design: A deidentified breastfeeding survey was sent to female faculty physicians at an academic children's hospital in 2020. Inclusion criteria included female faculty physicians who had given birth within the past 5 years. The responses of those who selected "yes" when asked if they had breastfed were analyzed. Results: Fifteen percent of respondents stated that they did not meet their breastfeeding goals. The most prevalent theme for both positive and negative factors in the qualitative analysis was pumping breast milk. Physician mothers provided key insight into (1) the impact of their role as physicians on their breastfeeding experience, (2) impact of their return to work on breastfeeding, and (3) ideas for improved lactation support. Conclusion: This study highlights the need to improve maternal and infant health by advocating for faculty physicians who are providing breast milk for their children. Advocacy efforts should focus on improving conditions for breast milk pumping and for effective policies around return to work after delivery. Further development and study of individualized breastfeeding support plans for physician mothers is needed.

Superior Detection of Faces in Male Infants at 2 Months

Females generally attend more to social information than males; however, little is known about the early development of these sex differences. With eye tracking, 2-month olds' (N = 101; 44 females) social orienting to faces was measured within four-item image arrays. Infants were more likely to detect human faces compared to objects, suggesting a functional face detection system. Unexpectedly, males looked longer at human faces than females, and only males looked faster and longer at human faces compared to objects. Females, in contrast, looked less at human faces relative to animal faces and objects, appearing socially disinterested. Notably, this is the first report of a male face detection advantage at any age. These findings suggest a unique stage in early infant social development.

Prolonged Auditory Brainstem Response in Universal Hearing Screening of Newborns with Autism Spectrum Disorder

Previous studies report prolonged auditory brainstem response (ABR) in children and adults with autism spectrum disorder (ASD). Despite its promise as a biomarker, it is unclear whether healthy newborns who later develop ASD also show ABR abnormalities. In the current study, we extracted ABR data on 139,154 newborns from their Universal Newborn Hearing Screening, including 321 newborns who were later diagnosed with ASD. We found that the ASD newborns had significant prolongations of their ABR phase and V‐negative latency compared with the non‐ASD newborns. Newborns in the ASD group also exhibited greater variance in their latencies compared to previous studies in older ASD samples, likely due in part to the low intensity of the ABR stimulus. These findings suggest that newborns display neurophysiological variation associated with ASD at birth. Future studies with higher‐intensity stimulus ABRs may allow more accurate predictions of ASD risk, which could augment the universal ABR test that currently screens millions of newborns worldwide.

Lay Summary

Children with autism spectrum disorder (ASD) have slow brain responses to sounds. We examined these brain responses from newborns' hearing tests and found that newborns who were later diagnosed with autism also had slower brain responses to sounds. Future studies might use these findings to better predict autism risk, with a hearing test that is already used on millions of newborns worldwide.

Human and monkey infant attention to dynamic social and nonsocial stimuli

The present study explored behavioral norms for infant social attention in typically developing human and nonhuman primate infants. We examined the normative development of attention to dynamic social and nonsocial stimuli longitudinally in macaques (Macaca mulatta) at 1, 3, and 5 months of age (N = 75) and humans at 2, 4, 6, 8, and 13 months of age (N = 69) using eye tracking. All infants viewed concurrently played silent videos-one social video and one nonsocial video. Both macaque and human infants were faster to look to the social than the nonsocial stimulus, and both species grew faster to orient to the social stimulus with age. Further, macaque infants' social attention increased linearly from 1 to 5 months. In contrast, human infants displayed a nonlinear pattern of social interest, with initially greater attention to the social stimulus, followed by a period of greater interest in the nonsocial stimulus, and then a rise in social interest from 6 to 13 months. Overall, human infants looked longer than macaque infants, suggesting humans have more sustained attention in the first year of life. These findings highlight potential species similarities and differences, and reflect a first step in establishing baseline patterns of early social attention development.

Quantifying Sources of Variability in Infancy Research Using the Infant-Directed-Speech Preference

Psychological scientists have become increasingly concerned with issues related to methodology and replicability, and infancy researchers in particular face specific challenges related to replicability: For example, high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations. Addressing these concerns, we report on a large-scale, multisite study aimed at (a) assessing the overall replicability of a single theoretically important phenomenon and (b) examining methodological, cultural, and developmental moderators. We focus on infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). Stimuli of mothers speaking to their infants and to an adult in North American English were created using seminaturalistic laboratory-based audio recordings. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, Australia, and Asia using the three common methods for measuring infants’ discrimination (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s d) was 0.35, 95% confidence interval = [0.29, 0.42], which was reliably above zero but smaller than the meta-analytic mean computed from previous literature (0.67). The IDS preference was significantly stronger in older children, in those children for whom the stimuli matched their native language and dialect, and in data from labs using the head-turn preference procedure. Together, these findings replicate the IDS preference but suggest that its magnitude is modulated by development, native-language experience, and testing procedure.

Infant rhesus macaque (Macaca mulatta) personality and subjective well-being

Infant temperament is theorized to lay the foundation for adult personality; however, many questions remain regarding personality in infancy, including the number of dimensions, extent to which they are adult-like, and their relation to other outcomes, such as mental and physical health. Here we tested whether adult-like personality dimensions are already present in infancy in a nonhuman primate species. We measured personality and subjective well-being in 7-month-old rhesus macaques (N = 55) using the Hominoid Personality Questionnaire and Subjective Well-Being Questionnaire, both of which were developed for adult primates based on human measures. Multiple human raters, who provided infants with daily care since birth, independently rated each infant. We found high interrater reliability. Results from a parallel analysis and scree plot indicated a five component structure, which, using principal components analysis, we found to be comprised of dimensions relating to Openness (e.g., curiosity, inquisitive, playfulness), Assertiveness (e.g., dominance, bullying, aggressive), Anxiety (e.g., vigilance, fearful), Friendliness (e.g., sociable, affectionate, sympathetic), and Intellect (e.g., organized, not erratic). These components are largely analogous to those in adult macaques, suggesting remarkably stable structural personality components across the lifespan. Infant macaques' subjective well-being positively correlates with Openness and Assertiveness and negatively correlated with Anxiety, similar to findings in adult macaques and other primates. Together, these findings suggest that, in macaques, infant personality dimensions may be conceptually related to adult personality and challenge the view that infant temperament may be disorganized and not as meaningful as adult personality. Further research is necessary to explore the antecedents, predictive validity, and stability of these personality components across situations and with development.

Social touch alters newborn monkey behavior

In humans, infants respond positively to slow, gentle stroking-processed by C-tactile (CT) nerve fibers-by showing reductions in stress and increases in eye contact, smiling, and positive vocalizations. More frequent maternal touch is linked to greater activity and connectivity strength in social brain regions, and increases children's attention to and learning of faces. It has been theorized that touch may prime children for social interactions and set them on a path towards healthy social cognitive development. However, less is known about the effects of touch on young infants' psychological development, especially in the newborn period, a highly sensitive period of transition with rapid growth in sensory and social processing. It remains untested whether newborns can distinguish CT-targeted touch from other types of touch, or whether there are benefits of touch for newborns' social, emotional, or cognitive development. In the present study, we experimentally investigated the acute effects of touch in newborn monkeys, a common model for human social development. Rhesus macaques (Macaca mulatta), like humans, are highly social, have complex mother-infant interactions with frequent body contact for the first weeks of life, making them an excellent model of infant sociality. Infant monkeys in the present study were reared in a neonatal nursery, enabling control over their early environment, including all caregiver interactions. One-week-old macaque infants (N = 27) participated in three 5-minute counter-balanced caregiver interactions, all with mutual gaze: stroking head and shoulders (CT-targeted touch), stroking palms of hands and soles of feet (Non-CT touch), or no stroking (No-touch). Immediately following the interaction, infants watched social and nonsocial videos and picture arrays including faces and objects, while we tracked their visual attention with remote eye tracking. We found that, during the caregiver interactions, infants behaved differently while being touched compared to the no-touch condition, irrespective of the body part touched. Most notably, in both touch conditions, infants exhibited fewer stress-related behaviors-self-scratching, locomotion, and contact time with a comfort object-compared to when they were not touched. Following CT-targeted touch, infants were faster to orient to the picture arrays compared to the other interaction conditions, suggesting CT-targeted touch may activate or prime infants' attentional orienting system. In the No-touch condition infants attended longer to the nonsocial compared to the social video, possibly reflecting a baseline preference for nonsocial stimuli. In contrast, in both touch conditions, infants' looked equally to the social and nonsocial videos, suggesting that touch may influence the types of visual stimuli that hold infants' attention. Collectively, our results reveal that newborn macaques responded positively to touch, and touch appeared to influence some aspects of their subsequent attention, although we found limited evidence that these effects are mediated by CT fibers. These findings suggest that newborn touch may broadly support infants' psychological development, and may have early evolutionary roots, shared across primates. This study illustrates the unique insight offered by nonhuman primates for exploring early infant social touch, revealing that touch may positively affect emotional and attentional development as early as the newborn period.

Face detection in 2- to 6-month-old infants is influenced by gaze direction and species

Humans detect faces efficiently from a young age. Face detection is critical for infants to identify and learn from relevant social stimuli in their environments. Faces with eye contact are an especially salient stimulus, and attention to the eyes in infancy is linked to the emergence of later sociality. Despite the importance of both of these early social skills-attending to faces and attending to the eyes-surprisingly little is known about how they interact. We used eye tracking to explore whether eye contact influences infants' face detection. Longitudinally, we examined 2-, 4-, and 6-month-olds' (N = 65) visual scanning of complex image arrays with human and animal faces varying in eye contact and head orientation. Across all ages, infants displayed superior detection of faces with eye contact; however, this effect varied as a function of species and head orientation. Infants were more attentive to human than animal faces and were more sensitive to eye and head orientation for human faces compared to animal faces. Unexpectedly, human faces with both averted heads and eyes received the most attention. This pattern may reflect the early emergence of gaze following-the ability to look where another individual looks-which begins to develop around this age. Infants may be especially interested in averted gaze faces, providing early scaffolding for joint attention. This study represents the first investigation to document infants' attention patterns to faces systematically varying in their attentional states. Together, these findings suggest that infants develop early, specialized functional conspecific face detection.

Interindividual differences in neonatal sociality and emotionality predict juvenile social status in rhesus monkeys

In humans, socioeconomic status (SES) has profound outcomes on socio-emotional development and health. However, while much is known about the consequences of SES, little research has examined the predictors of SES due to the longitudinal nature of such studies. We sought to explore whether interindividual differences in neonatal sociality, temperament, and early social experiences predicted juvenile social status in rhesus monkeys (Macaca mulatta), as a proxy for SES in humans. We performed neonatal imitation tests in infants' first week of life and emotional reactivity assessments at 2 and 4 weeks of age. We examined whether these traits, as well as the rearing environment in the first 8 months of life (with the mother or with same-aged peers only) and maternal social status predicted juvenile (2-3 years old) social status following the formation of peer social groups at 8 months. We found that infants who exhibited higher rates of neonatal imitation and newborn emotional reactivity achieved higher social status as juveniles, as did infants who were reared with their mothers, compared to infants reared with peers. Maternal social status was only associated with juvenile status for infant dyads reared in the same maternal group, indicating that relative social relationships were transferred through social experience. These results suggest that neonatal imitation and emotional reactivity may reflect ingrained predispositions toward sociality that predict later outcomes, and that nonnormative social experiences can alter socio-developmental trajectories. Our results indicate that neonatal characteristics and early social experiences predict later social outcomes in adolescence, including gradients of social stratification.

Visual preferences for direct-gaze faces in infant macaques (Macaca mulatta) with limited face exposure

From birth, human and nonhuman primates attend more to faces with direct gaze compared with averted gaze, and previous studies report that attention to the eyes is linked to the emergence of later social skills. Here, we explored whether early experiences influence attraction to eye contact in infant macaques by examining their attention to face pairs varying in their gaze direction across the first 13 weeks of life. Infants raised by human caretakers had limited conspecific interactions (nursery-reared; N = 16) and were compared to infants raised in rich social environments (mother-reared; N = 20). Both groups looked longer to faces and the eyes of direct compared to averted-gaze faces. Looking to all faces and eyes also increased with age. Nursery-reared infants did not display age-associated increases in attention to direct-gaze faces specifically, suggesting that, while there may be an initial preference for direct-gaze faces from birth, social experiences may support its early development.

Who's my little monkey? Effects of infant-directed speech on visual retention in infant rhesus macaques

Both human and nonhuman primate adults use infant-directed facial and vocal expressions across many contexts when interacting with infants (e.g., feeding, playing). This infant-oriented style of communication, known as infant-directed speech (IDS), seems to benefit human infants in numerous ways, including facilitating language acquisition. Given the variety of contexts in which adults use IDS, we hypothesized that IDS supports learning beyond the linguistic domain and that these benefits may extend to nonhuman primates. We exposed 2.5-month-old rhesus macaque infants (N = 15) to IDS, adult-directed speech (ADS), and a non-social control (CTR) during a video presentation of unrelated stimuli. After a 5- or 60-minute delay, infants were shown the familiar video side-by-side with a novel video. Infants exhibited a novelty preference after the 5-minute delay, but not after the 60-minute delay, in the ADS and CTR conditions, and a novelty preference in the IDS condition only after the 60-minute delay. These results are the first to suggest that exposure to IDS affects infants' long-term memory, even in non-linguistic animals.

Use of a Smartphone App to Assess Neonatal Jaundice

BACKGROUND

The assessment of jaundice in outpatient neonates is problematic. Visual assessment is inaccurate, and more exact methodologies are cumbersome and/or expensive. Our goal in this study was to assess the accuracy of a technology based on the analysis of digital images of newborns obtained using a smartphone application called BiliCam.

METHODS

Paired BiliCam images and total serum bilirubin (TSB) levels were obtained in a diverse sample of newborns (<7 days old) at 7 sites across the United States. By using specialized software, data on color values in the images ("features") were extracted. Machine learning and regression analysis techniques were used to identify features for inclusion in models to predict an estimated bilirubin level for each newborn. The correlation between estimated bilirubin levels and TSB levels was calculated. In addition, the sensitivity and specificity of the estimated bilirubin levels in identifying newborns with high TSB levels were calculated by using 2 recommended decision rules for jaundice screening.

RESULTS

Estimated bilirubin levels were calculated and compared with TSB levels in a diverse sample of 530 newborns (20.8% African American, 26.3% Hispanic, and 21.2% Asian American). The overall correlation was 0.91, and correlations among white, African American, Hispanic, and Asian American newborns were 0.92, 0.90, 0.91, and 0.88, respectively. The sensitivities of BiliCam in identifying newborns with high TSB levels were 84.6% and 100%, respectively, by using 2 decision rules; specificities were 75.1% and 76.4%, respectively.

CONCLUSIONS

BiliCam provided accurate estimates of TSB values, demonstrating that an inexpensive technology that uses commodity smartphones could be used to effectively screen newborns for jaundice.

Handling newborn monkeys alters later exploratory, cognitive, and social behaviors

Touch is one of the first senses to develop and one of the earliest modalities for infant-caregiver communication. While studies have explored the benefits of infant touch in terms of physical health and growth, the effects of social touch on infant behavior are relatively unexplored. Here, we investigated the influence of neonatal handling on a variety of domains, including memory, novelty seeking, and social interest, in infant monkeys (Macaca mulatta; n=48) from 2 to 12 weeks of age. Neonates were randomly assigned to receive extra holding, with or without accompanying face-to-face interactions. Extra-handled infants, compared to standard-reared infants, exhibited less stress-related behavior and more locomotion around a novel environment, faster approach of novel objects, better working memory, and less fear towards a novel social partner. In sum, infants who received more tactile stimulation in the neonatal period subsequently demonstrated more advanced motor, social, and cognitive skills-particularly in contexts involving exploration of novelty-in the first three months of life. These data suggest that social touch may support behavioral development, offering promising possibilities for designing future early interventions, particularly for infants who are at heightened risk for social disorders.

Testing the arousal hypothesis of neonatal imitation in infant rhesus macaques

Neonatal imitation is the matching of (often facial) gestures by newborn infants. Some studies suggest that performance of facial gestures is due to general arousal, which may produce false positives on neonatal imitation assessments. Here we examine whether arousal is linked to facial gesturing in newborn infant rhesus macaques (Macaca mulatta). We tested 163 infants in a neonatal imitation paradigm in their first postnatal week and analyzed their lipsmacking gestures (a rapid opening and closing of the mouth), tongue protrusion gestures, and yawn responses (a measure of arousal). Arousal increased during dynamic stimulus presentation compared to the static baseline across all conditions, and arousal was higher in the facial gestures conditions than the nonsocial control condition. However, even after controlling for arousal, we found a condition-specific increase in facial gestures in infants who matched lipsmacking and tongue protrusion gestures. Thus, we found no support for the arousal hypothesis. Consistent with reports in human newborns, imitators’ propensity to match facial gestures is based on abilities that go beyond mere arousal. We discuss optimal testing conditions to minimize potentially confounding effects of arousal on measurements of neonatal imitation.

Preference for facial averageness: Evidence for a common mechanism in human and macaque infants

Human adults and infants show a preference for average faces, which could stem from a general processing mechanism and may be shared among primates. However, little is known about preference for facial averageness in monkeys. We used a comparative developmental approach and eye-tracking methodology to assess visual attention in human and macaque infants to faces naturally varying in their distance from a prototypical face. In Experiment 1, we examined the preference for faces relatively close to or far from the prototype in 12-month-old human infants with human adult female faces. Infants preferred faces closer to the average than faces farther from it. In Experiment 2, we measured the looking time of 3-month-old rhesus macaques (Macaca mulatta) viewing macaque faces varying in their distance from the prototype. Like human infants, macaque infants looked longer to faces closer to the average. In Experiments 3 and 4, both species were presented with unfamiliar categories of faces (i.e., macaque infants tested with adult macaque faces; human infants and adults tested with infant macaque faces) and showed no prototype preferences, suggesting that the prototypicality effect is experience-dependent. Overall, the findings suggest a common processing mechanism across species, leading to averageness preferences in primates.

Acute oxytocin improves memory and gaze following in male but not female nursery-reared infant macaques

RATIONALE

Exogenous oxytocin administration is widely reported to improve social cognition in human and nonhuman primate adults. Risk factors of impaired social cognition, however, emerge in infancy. Early interventions-when plasticity is greatest-are critical to reverse negative outcomes.

OBJECTIVE

We tested the hypothesis that oxytocin may exert similar positive effects on infant social cognition, as in adults. To test this idea, we assessed the effectiveness of acute, aerosolized oxytocin on two foundational social cognitive skills: working memory (i.e., ability to briefly hold and process information) and social gaze (i.e., tracking the direction of others' gaze) in 1-month-old nursery-reared macaque monkeys (Macaca mulatta). We did not predict sex differences, but we included sex as a factor in our analyses to test whether our effects would be generalizable across both males and females.

RESULTS

In a double-blind, placebo-controlled design, we found that females were more socially skilled at baseline compared to males, and that oxytocin improved working memory and gaze following, but only in males.

CONCLUSIONS

These sex differences, while unexpected, may be due to interactions with gonadal steroids and may be relevant to sexually dimorphic disorders of social cognition, such as male-biased autism spectrum disorder, for which oxytocin has been proposed as a potential treatment. In sum, we report the first evidence that oxytocin may influence primate infant cognitive abilities. Moreover, these behavioral effects appear sexually dimorphic, highlighting the importance of considering sex differences. Oxytocin effects observed in one sex may not be generalizable to the other sex.

Face Detection and the Development of Own-Species Bias in Infant Macaques

In visually complex environments, numerous items compete for attention. Infants may exhibit attentional efficiency-privileged detection, attention capture, and holding-for face-like stimuli. However, it remains unknown when these biases develop and what role, if any, experience plays in this emerging skill. Here, nursery-reared infant macaques' (Macaca mulatta; n = 10) attention to faces in 10-item arrays of nonfaces was measured using eye tracking. With limited face experience, 3-week-old monkeys were more likely to detect faces and looked longer at faces compared to nonfaces, suggesting a robust face detection system. By 3 months, after peer exposure, infants looked faster to conspecific faces but not heterospecific faces, suggesting an own-species bias in face attention capture, consistent with perceptual attunement.

Neonatal imitation predicts infant rhesus macaque (Macaca mulatta) social and anxiety-related behaviours at one year

The identification of early markers that predict the development of specific social trajectories is critical to understand the developmental and neurobiological underpinnings of healthy social development. We investigated, in infant rhesus macaques (Macaca mulatta), whether newborns’ capacity to imitate facial gestures is a valid predictive marker for the emergence of social competencies later in development, at one year of age. Here we first assessed whether infant macaques (N = 126) imitate lipsmacking gestures (a macaque affiliative expression) performed by a human experimenter in their first week of life. We then collected data on infants’ social interactions (aggression, grooming, and play) and self-scratching (a proxy indicator of anxiety) at 11–14 months when infants were transferred into a new enclosure with a large social group. Our results show that neonatal imitators exhibit more dominant behaviours, are less anxious, and, for males only, spend more time in play at one year old. These findings suggest that neonatal imitation may be an early predictor of infant sociality and may help identify infants at risk of neurodevelopmental social deficits.

Neonatal face-to-face interactions promote later social behaviour in infant rhesus monkeys

In primates, including humans, mothers engage in face-to-face interactions with their infants, with frequencies varying both within and across species. However, the impact of this variation in face-to-face interactions on infant social development is unclear. Here we report that infant monkeys (Macaca mulatta) who engaged in more neonatal face-to-face interactions with mothers have increased social interactions at 2 and 5 months. In a controlled experiment, we show that this effect is not due to physical contact alone: monkeys randomly assigned to receive additional neonatal face-to-face interactions (mutual gaze and intermittent lip-smacking) with human caregivers display increased social interest at 2 months, compared with monkeys who received only additional handling. These studies suggest that face-to-face interactions from birth promote young primate social interest and competency.

Utility of Decision Rules for Transcutaneous Bilirubin Measurements

BACKGROUND

Transcutaneous bilirubin (TcB) meters are widely used for screening newborns for jaundice, with a total serum bilirubin (TSB) measurement indicated when the TcB value is classified as "positive" by using a decision rule. The goal of our study was to assess the clinical utility of 3 recommended TcB screening decision rules.

METHODS

Paired TcB/TSB measurements were collected at 34 newborn nursery sites. At 27 sites (sample 1), newborns were routinely screened with a TcB measurement. For sample 2, sites that typically screen with TSB levels also obtained a TcB measurement for the study. Three decision rules to define a positive TcB measurement were evaluated: ≥75th percentile on the Bhutani nomogram, 70% of the phototherapy level, and within 3 mg/dL of the phototherapy threshold. The primary outcome was a TSB level at/above the phototherapy threshold. The rate of false-negative TcB screens and percentage of blood draws avoided were calculated for each decision rule.

RESULTS

For sample 1, data were analyzed on 911 paired TcB-TSB measurements from a total of 8316 TcB measurements. False-negative rates were <10% with all decision rules; none identified all 31 newborns with a TSB level at/above the phototherapy threshold. The percentage of blood draws avoided ranged from 79.4% to 90.7%. In sample 2, each rule correctly identified all 8 newborns with TSB levels at/above the phototherapy threshold.

CONCLUSIONS

Although all of the decision rules can be used effectively to screen newborns for jaundice, each will "miss" some infants with a TSB level at/above the phototherapy threshold.

Neonatal imitation and early social experience predict gaze following abilities in infant monkeys

Individuals vary in their social skills and motivation, the causes of which remain largely unknown. Here we investigated whether an individual’s propensity to interact with others measured within days after birth, and differences in infants’ early social environment, may predict a later social skill. Specifically, we tested whether neonatal imitation—newborns’ capacity to match modelled actions—and social experience in the first months of life predict gaze following (directing attention to locations where others look), in infant macaques (Macaca mulatta; n = 119). Facial gesture imitation in the first week of life predicted gaze following at 7 months of age. Imitators were better at gaze following than non-imitators, suggesting neonatal imitation may be an early marker predicting socio-cognitive functioning. In addition, infants with rich social environments outperformed infants with less socialization, suggesting early social experiences also support the development of infants’ gaze following competence. The present study offers compelling evidence that an individual difference present from birth predicts a functional social cognitive skill in later infancy. In addition, this foundational skill—gaze following—is plastic, and can be improved through social interactions, providing infants with a strong foundation for later social interaction and learning.

Experience-independent sex differences in newborn macaques: Females are more social than males

Human females exhibit greater social interest and skills relative to males, appearing in infancy, suggesting biological roots; however, male and female infants may be treated differently, potentially causing or amplifying sex differences. Here, we tested whether sex differences in social motivation emerge in infant monkeys (n = 48) reared in a controlled postnatal environment. Compared to males, females at 2-3 weeks looked more at conspecifics' faces (d = 0.65), especially the eyes (d = 1.09), and at 4-5 weeks exhibited more affiliative behaviors (d = 0.64), including gesturing, looking, and proximity to familiar and unfamiliar human caretakers. In sum, converging evidence from humans and monkeys suggests that female infants are more social than males in the first weeks of life, and that such differences may arise independent of postnatal experience. Individual differences in social interest have wide-ranging developmental consequences, impacting infants' social interaction quality and opportunities for learning. Understanding the evolution of sex differences and their developmental emergence is necessary to best support infants with varying levels of sociality.

Relations between infants' emerging reach-grasp competence and event-related desynchronization in EEG

Recent reports of similar patterns of brain electrical activity (electroencephalogram: EEG) during action execution and observation, recorded from scalp locations over motor-related regions in infants and adults, have raised the possibility that two foundational abilities--controlling one's own intentional actions and perceiving others' actions--may be integrally related during ontogeny. However, to our knowledge, there are no published reports of the relations between developments in motor skill (i.e. recording actual motor skill performance) and EEG during both action execution and action observation. In the present study we collected EEG from 21 9-month-olds who were given opportunities to reach for toys and who also observed an experimenter reach for toys. Event-related desynchronization (ERD) was computed from the EEG during the reaching events. We assessed infants' reaching-grasping competence, including reach latency, errors, preshaping of the hand, and bimanual reaches, and found that desynchronization recorded in scalp electrodes over motor-related regions during action observation was associated with action competence during execution. Infants who were more competent reachers, compared to less competent reachers, exhibited greater ERD while observing reaching-grasping. These results provide initial evidence for an early emerging neural system integrating one's own actions with the perception of others' actions.

Efficient human face detection in infancy

Adults detect conspecific faces more efficiently than heterospecific faces; however, the development of this own-species bias (OSB) remains unexplored. We tested whether 6- and 11-month-olds exhibit OSB in their attention to human and animal faces in complex visual displays with high perceptual load (25 images competing for attention). Infants (n = 48) and adults (n = 43) passively viewed arrays containing a face among 24 non-face distractors while we measured their gaze with remote eye tracking. While OSB is typically not observed until about 9 months, we found that, already by 6 months, human faces were more likely to be detected, were detected more quickly (attention capture), and received longer looks (attention holding) than animal faces. These data suggest that 6-month-olds already exhibit OSB in face detection efficiency, consistent with perceptual attunement. This specialization may reflect the biological importance of detecting conspecific faces, a foundational ability for early social interactions.

Evolutionary relevance and experience contribute to face discrimination in infant macaques (Macaca mulatta)

In human children and adults, familiar face types-typically own-age and own-species faces-are discriminated better than other face types; however, human infants do not appear to exhibit an own-age bias, but instead better discriminate adult faces, which they see more often. There are two possible explanations for this pattern: Perceptual attunement, which predicts advantages in discrimination for the most-experienced face types; additionally or alternatively, there may be an experience-independent bias for infants to discriminate own-species faces, an adaptation for evolutionarily relevant faces. These possibilities have not been disentangled in studies thus far, which did not control infants' early experiences with faces. In the present study, we tested these predictions in infant macaques (Macaca mulatta) reared under controlled environments, not exposed to adult conspecifics. We measured newborns' (15-25 days; n = 27) and 6- to 7-month-olds' (n = 35) discrimination of human and macaque faces of three ages-young infants, old infants, and adults-in a visual paired comparison task. We found that 6- to 7-month-olds were the best at discriminating adult macaque faces; however, in the first few seconds of looking, additionally discriminated familiar face types-same-aged peer and adult human faces-highlighting the importance of experience with certain face categories. The present data suggest that macaque infants possess both experience-independent and experientially tuned face biases. In human infants, early face skills may likewise be driven by both experience and evolutionary relevance; future studies should consider both of these factors.

Early Social Experience Affects Neural Activity to Affiliative Facial Gestures in Newborn Nonhuman Primates

A fundamental issue in cognitive neuroscience is how the brain encodes the actions and intentions of others. The discovery of an action-production-perception mechanism underpinning such a capacity advanced our knowledge of how these processes occur; however, no study has examined how the early postnatal environment may shape action-production-perception. Here, we examined the effects of social experience on action-production-perception in 3-day-old rhesus macaques that were raised either with or without their biological mothers. We measured the neonatal imitation skills and brain electrical activity responses, while infants produced and observed facial gestures. We hypothesized that early social experiences may shape brain activity, as assessed via electroencephalogram suppression in the α band (5-7 Hz in infants, known as the mu rhythm) during action observation, and lead to more proficient imitation skills. Consistent with this hypothesis, the infants reared by their mothers were more likely to imitate lipsmacking (LS) - a natural, affiliative gesture - and exhibited greater mu rhythm desynchronization while viewing LS gestures than the nursery-reared infants. These effects were not found in response to tongue protrusion, a meaningless gesture, or a nonsocial control. These data suggest that socially enriched early experiences in the first days after birth increase brain sensitivity to socially relevant actions. © 2015 S. Karger AG, Basel.

Development of space perception in relation to the maturation of the motor system in infant rhesus macaques (Macaca mulatta)

To act on the environment, organisms must perceive object locations in relation to their body. Several neuroscientific studies provide evidence of neural circuits that selectively represent space within reach (i.e., peripersonal) and space outside of reach (i.e., extrapersonal). However, the developmental emergence of these space representations remains largely unexplored. We investigated the development of space coding in infant macaques and found that they exhibit different motor strategies and hand configurations depending on the objects' size and location. Reaching-grasping improved from 2 to 4 weeks of age, suggesting a broadly defined perceptual body schema at birth, modified by the acquisition and refinement of motor skills through early sensorimotor experience, enabling the development of a mature capacity for coding space.

Discrepancies between transcutaneous and serum bilirubin measurements

OBJECTIVE

To characterize discrepancies between transcutaneous bilirubin (TcB) measurements and total serum bilirubin (TSB) levels among newborns receiving care at multiple nursery sites across the United States.

METHODS

Medical records were reviewed to obtain data on all TcB measurements collected during two 2-week periods on neonates admitted to participating newborn nurseries. Data on TSB levels obtained within 2 hours of a TcB measurement were also abstracted. TcB--TSB differences and correlations between the values were determined. Data on demographic information for individual newborns and TcB screening practices for each nursery were also collected. Multivariate regression analysis was used to identify characteristics independently associated with the TcB--TSB difference.

RESULTS

Data on 8319 TcB measurements were collected at 27 nursery sites; 925 TSB levels were matched to a TcB value. The mean TcB--TSB difference was 0.84 ± 1.78 mg/dL, and the correlation between paired measurements was 0.78. In the multivariate analysis, TcB--TSB differences were 0.67 mg/dL higher in African-American newborns than in neonates of other races (P < .001). The TcB--TSB difference also varied significantly based on brand of TcB meter used and hour of age of the infant. For 2.2% of paired measurements, the TcB measurement underestimated the TSB level by ≥ 3 mg/dL.

CONCLUSIONS

During routine clinical care, TcB measurement provided a reasonable estimate of TSB levels in healthy newborns. Discrepancies between TcB and TSB levels were increased in African-American newborns and varied based on brand of meter used.

Neonatal imitation predicts how infants engage with faces

In human infants, neonatal imitation and preferences for eyes are both associated with later social and communicative skills, yet the relationship between these abilities remains unexplored. Here we investigated whether neonatal imitation predicts facial viewing patterns in infant rhesus macaques. We first assessed infant macaques for lipsmacking (a core affiliative gesture) and tongue protrusion imitation in the first week of life. When infants were 10-28 days old, we presented them with an animated macaque avatar displaying a still face followed by lipsmacking or tongue protrusion movements. Using eye tracking technology, we found that macaque infants generally looked equally at the eyes and mouth during gesture presentation, but only lipsmacking-imitators showed significantly more looking at the eyes of the neutral still face. These results suggest that neonatal imitation performance may be an early measure of social attention biases and might potentially facilitate the identification of infants at risk for atypical social development.

The mirror neuron system as revealed through neonatal imitation: presence from birth, predictive power and evidence of plasticity

There is strong evidence that neonates imitate previously unseen behaviours. These behaviours are predominantly used in social interactions, demonstrating neonates' ability and motivation to engage with others. Research on neonatal imitation can provide a wealth of information about the early mirror neuron system (MNS), namely its functional characteristics, its plasticity from birth and its relation to skills later in development. Although numerous studies document the existence of neonatal imitation in the laboratory, little is known about its natural occurrence during parent-infant interactions and its plasticity as a consequence of experience. We review these critical aspects of imitation, which we argue are necessary for understanding the early action-perception system. We address common criticisms and misunderstandings about neonatal imitation and discuss methodological differences among studies. Recent work reveals that individual differences in neonatal imitation positively correlate with later social, cognitive and motor development. We propose that such variation in neonatal imitation could reflect important individual differences of the MNS. Although postnatal experience is not necessary for imitation, we present evidence that neonatal imitation is influenced by experience in the first week of life.

Visual search efficiency is greater for human faces compared to animal faces

The Animate Monitoring Hypothesis proposes that humans and animals were the most important categories of visual stimuli for ancestral humans to monitor, as they presented important challenges and opportunities for survival and reproduction; however, it remains unknown whether animal faces are located as efficiently as human faces. We tested this hypothesis by examining whether human, primate, and mammal faces elicit similar searches, or whether human faces are privileged. In the first three experiments, participants located a target (human, primate, or mammal face) among distractors (non-face objects). We found fixations on human faces were faster and more accurate than fixations on primate faces, even when controlling for search category specificity. A final experiment revealed that, even when task-irrelevant, human faces slowed searches for non-faces, suggesting some bottom-up processing may be responsible for the human face search efficiency advantage.

Mirror neurons through the lens of epigenetics

The consensus view in mirror neuron research is that mirror neurons comprise a uniform, stable execution-observation matching system. In this opinion article, we argue that, in light of recent evidence, this is at best an incomplete and oversimplified view of mirror neurons, where activity is actually variable and more plastic than previously theorized. We propose an epigenetic account for understanding developmental changes in sensorimotor systems, including variations in mirror neuron activity. Although associative and genetic accounts fail to consider the complexity of genetic and nongenetic interactions, we propose a new evolutionary developmental biology (evo-devo) perspective, which predicts that environmental differences early in development should produce variations in mirror neuron response patterns, tuning them to the social environment.

Visual attention during neonatal imitation in newborn macaque monkeys

Previous studies suggest that about 50% of rhesus macaque infants engage in neonatal imitation of facial gestures. Here we measured whether individual differences in newborn macaques' (n = 49) visual attention may explain why some infants imitate lipsmacking (LPS) and tongue protrusion (TP) gestures. LPS imitators, but not TP imitators, looked more to a human experimenter's face and to a control stimulus compared to nonimitators (p = .017). LPS imitation was equally accurate when infants were looking at faces and when they were looking away (p = .221); TP imitation was more accurate when infants were looking at faces (p = .001). Potentially, less attention is necessary for LPS imitation compared to TP imitation, as LPS is part of macaques' natural communicative repertoire. These findings suggest that facial gestures may differentially engage imitators and nonimitators, and infants' visual attention during neonatal assessments may uncover the conditions that support this skill.

Sensitivity to first-order relations of facial elements in infant rhesus macaques

Faces are visually attractive to both human and nonhuman primates. Human neonates are thought to have a broad template for faces at birth and prefer face-like to non-face-like stimuli. To better compare developmental trajectories of face processing phylogenetically, here we investigated preferences for face-like stimuli in infant rhesus macaques using photographs of real faces. We presented infant macaques aged 15-25days with human, macaque, and abstract faces with both normal and linear arrangements of facial features, and measured infants' gaze durations, number of fixations, and latency to look to each face using eye-tracking technology. There was an overall preference for normal over linear facial arrangements for abstract and monkey faces, but not human faces. Moreover, infant macaques looked less at monkey faces than at abstract or human faces. These results suggest that species and facial configurations affect face processing in infant macaques, and we discuss potential explanations for these findings. Further, carefully controlled studies are required to ascertain whether infant macaques' face template can be considered as broad as human infants' face template.

Intrarenal localization of angiotensinogen mRNA by RNA-DNA dot-blot hybridization

The renal renin-angiotensin system plays an important role in the control of renal hemodynamics and in the etiology of some types of hypertension. Angiotensinogen is the prohormone for angiotensins I and II. In the present communication, we report for the first time the presence of mRNA coding for angiotensinogen in the kidney. Indeed, the intrarenal location appears to be predominantly in the renal medulla. Additionally, an investigation of the effect of uninephrectomy on the intrarenal angiotensinogen mRNA suggests that regulation of mRNA levels in the kidney does occur.