Social and Emotional Abilities

One fundamental question pursued in my work is what makes humans such intensely social beings. To shed light on this question, my research has probed the developmental and neural origins of our social capacities. In particular, I have studied the early emergence of the social and emotional abilities that enable infants to understand and interact with others. By using non-invasive and child-friendly methods such as electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS) and eye-tracking technology, I have identified a set of key principles that guide the development of social brain functions in the first year of life and provide a framework for further research in this domain. These principles are: (1) self-relevance, (2) joint engagement, (3) predictability, (4) categorization, (5) discrimination, and (6) integration. 

For example, my work has shown that a young infant’s brain selectively responds to cues that index that another person wants to interact with them (self-relevance), detects what the interaction is about (joint engagement), and predicts the next step of an ongoing action (predictability). Moreover, my research has provided evidence for the emergence of infants’ ability to flexibly use facial, vocal, and body cues to identify what kind of agent they are interacting with (categorization), distinguish between different emotional states that a particular agent experiences (discrimination), and match information across processing channels and modalities (integration). 

Critically, I have argued that the key principles of the developing brain function identified by this body of work can be further classified with respect to their domain-specificity (specifically social versus domain-general), developmental timing (early versus late), and brain localization (prefrontal versus temporal regions). On the basis of my own empirical work and work conducted in other infant labs, I have put forward a theoretical proposal that distinguishes between primary and secondary principles of developing social brain functions, whereby primary principles (such as self-relevance and joint engagement) serve as a precondition, and secondary principles (such as categorization and discrimination) are an outcome of the infant’s brain preparedness to interact with, learn from, and cooperate with others.

Conscious and Unconscious Facial Information Processing 

Most of my research on social perception in infancy has focused on how changeable facial cues, such as emotional expressions and eye gaze, are processed in the infant brain. More recently, we have been able to extend this line of work by investigating what distinguishes conscious from unconscious facial information processing and what social cues infants detect from faces even in the absence of conscious perception. 

This research has shed light on the nature of the processes that underlie infants’ developing social capacities and provides evidence for the existence and emergence of adult-like (automatic) facial information processing in infancy. In addition, we have begun to elucidate infants’ processing of unchangeable (invariant) facial information linked to face evaluation and character trait judgements in children and adults, especially with respect to a person’s trustworthiness. Findings from these studies show that infants engage brain processes linked to emotion discrimination when distinguishing between faces varying in their trustworthiness and display a behavioral preference for trustworthy faces over untrustworthy faces. Similar to the discrimination of changeable (emotion and gaze cues) facial cues, neural discrimination of faces varying in their trustworthiness occurs independent of conscious perception of the face.

Functional Activity in the Prefrontal Cortex 

Among the specific brain areas involved in the adult social brain network, functional activity in the prefrontal cortex (PFC), particularly the medial PFC (mPFC), is of special importance for human social cognition and behavior. However, it has long been thought that the PFC is functionally silent during infancy, and little was known about the role of the PFC in the early development of social cognition. 

My neuroimaging work with infants provides evidence that the mPFC exhibits functional activation much earlier than previously thought, suggesting that the mPFC is involved in social information processing from early in life and proactively contributes to social and cognitive development during infancy. This line of infant neuroimaging work has helped to close a gap between the extensive behavioral work showing rather sophisticated social cognitive capacities in infants and research with adults and adolescents implicating mPFC in social cognition and theory of mind.  

Cooperative Behavior 

One pertinent question that arises from our research on the development of social perception and cognition in infancy is whether and how these early developing capacities relate to overt social behavior. We have begun to address this issue by examining the neurodevelopmental bases of early forms of cooperative behavior such as prosocial behavior. For example, in a longitudinal study, we were able to show that variability in infants’ responsiveness to others in distress predicts differences in helping behavior in toddlerhood. Moreover, we were able to demonstrate that this link between responding to others in distress and cooperative behavior continues to exist beyond infancy and is seen across cultures as shown by work with preschool children in Germany and India. 

In another study, we showed that: (a) toddlers recognize the specific need of the person and provide help accordingly, (b) changes in toddlers’ internal arousal (measured through pupil dilation) to seeing another person needing help was linked to their helping behavior, and (c) when prevented from helping themselves, toddlers’ internal arousal would only decline when viewing the person in need getting appropriate help. This line of work contributes to the emerging view that infants and children genuinely care about others in need and distress, but also that a caring continuum exists, which underpins variability in (pro)social behavior.

Oxytocin System

Much of my recent and ongoing research is concerned with capturing and understanding variability in social brain function and behavior during infancy with a specific focus on the oxytocin system. Our work suggests that early experience— particularly breastfeeding—interacts with oxytocin genetics, accounting for individual differences in social attention. 

We have also shown that individual differences in social functioning emerge in the context of epigenetic modification of the oxytocin receptor gene (OXTR) and are plastically shaped by experience. For instance, we found that changes in methylation of OXTR during infancy were predicted by maternal engagement and in turn associated with individual differences in behavioral temperament and social brain function among infants. Notably, mothers’ methylation levels of OXTR did not change during the same period of time. This provides evidence for an early window of environmental epigenetic regulation of the oxytocin system in human infancy.