The newborn period -- the first four weeks after birth -- is a special time in development. Newborns attend to, engage with, learn from, and bond with people. In this project, we asked: Why are some newborns more social than others and how can we best measure this? We developed new measures to begin to establish what healthy social behavior looks like. Ultimately, we aim to better predict healthy social development. Using longitudinal designs (following newborns as they grow up across the first year) we developed new ways to capture infant sociality, to improve the measurement of subtle differences among individuals. Overall, we found stable individual differences in early infant sociality across contexts and over time. That is, infants who showed more prosocial behavior in one setting also showed more prosociality in another setting. These findings highlight potential avenues to detect early disruptions to social development.

Neonatal Imitation: Meaningful Individual Differences. One behavior of interest is neonatal imitation (newborns' ability to match behaviors). We observed positive associations between human neonatal imitation and infants' other social behaviors, including their positive emotions while interacting with people and their social attention (e.g., how much they looked at faces). These findings suggest neonatal imitation may be a useful early marker of infant sociability in humans, similar to previous reports in monkeys. Efforts are underway to expand this study of neonatal imitation to a larger and more diverse worldwide sample through ManyBabies, a global consortium of developmental researchers (https://manybabies.org/MB6).

Newborn Facial Behavior: Automatic Coding with Machine Learning. One challenge of studying neonatal imitation is the laboriousness and subjectivity involved in identifying infant behaviors, which may unintentionally lead to bias. Automated measurement approaches, in contrast, have the potential to objectively quantify infant behaviors. We developed an approach to automatically score newborns' facial expressions, focused on infant mouth opening, a behavior commonly used in neonatal imitation studies. We used a computer vision algorithm to automatically track and register newborns' faces. Facial landmark coordinates were input into a classifier that we trained to recognize mouth opening. Our results highlight the potential of automated measurement approaches for objectively identifying newborns' mouth openings, increasing the efficiency and objectivity of infant behavioral research.

Improving Measurement of Visual Attention. Eye-tracking is a widely used method in infant research to track where infants are looking, yet little is understood about the accuracy of this tracking, particularly in the first months after birth. We examined how the calibration method and adjustments to data processing (areas of interest size and duration) changed the accuracy of this measure in a cross-species longitudinal study. We reported ways to improve the capture of human and monkey infants' gaze behaviors, published in Behavior Research Methods.

Pupil Dilation Reveals Infants' Internal States. We discovered that infants' level of pupil dilation may index their motivation and fear during interactions. In one study, we found stable individual differences in infants' pupil dilation predicted the development of gaze following, infants' ability to look where another individual looks, which is a foundational social skill. In another study, we explored infants' fearfulness to strangers. We discovered that infants' pupil dilation reflects the development of a fearful temperament. These findings, published in the journals Infancy and Developmental Psychobiology, may facilitate the identification of, and interventions for, social disruptions.

Salivary Oxytocin is Linked to Infants' Prosociality. Oxytocin is a neuropeptide that is linked to social behavior in adults. Yet, the early development of oxytocin is poorly understood. We found that salivary oxytocin may be a reliable measure of stable individual differences related to human infants' social development across the first year. Infants with higher levels of salivary oxytocin displayed more positive emotions during social interactions, a finding that we presented at the International Congress of Infant Studies. Salivary oxytocin may be a promising biomarker tied to early infant sociality.

Auditory Brainstem Response: Marker of Developmental Risk. We discovered that, at birth, newborns who are later diagnosed with a developmental disability, such as autism, process sounds differently compared to typically developing newborns. These tools are not yet accurate enough for correctly diagnosing individuals and therefore require further refinement and testing. However, our findings, published in PNAS Nexus, Autism Research, and the Journal of Autism and Developmental Disorders, offer clues about perceptual differences present at birth.

Mentoring Future Scientists. This project provided extensive training to 5 graduate students and 46 undergraduate students, generating 3 doctoral dissertations, 3 master's theses, 10 honors theses papers, and 15 summer student projects in a new summer research program for undergraduates. Students from groups underrepresented in science were trained in all aspects of developmental science research, including coauthoring manuscripts and learning about career paths, aiming to increase students' interest in science and inspire future generations of scientists.

Last Modified: 06/29/2023
Modified by: Elizabeth A Simpson