ABSTRACT
In infants, as in adults, social context is known to influence attentional allocation during communication. The sharing of attention between individuals potentiates learning, but little is understood about the interpersonal neural mechanisms that support this process. Recently, it has been demonstrated that during spoken communication, spontaneous neural coupling (temporal synchronization) arises between speaker and listener, and their coupling strength predicts communicative success. Here, we assess whether gaze, a salient cue that elicits joint attention, moderates endogenous levels of neural coupling in adult-infant speaker-listener dyads. Electroencephalography (EEG) was concurrently measured in 19 adult experimenter-infant dyads at left and right central electrode locations. The adult sang nursery rhymes to the infant whilst either looking directly at the infant, or with her gaze averted by 20°. Gaze-related changes in adult-infant neural network connectivity were measured using Partial Directed Coherence (PDC), a statistical measure of causality and directional influence. Our results showed that bi-directional connectivity between adults and infants was significantly higher during periods of Direct than Indirect gaze in Theta, Alpha and Beta EEG bands. Further analyses suggested that these effects were not attributable to differences in task engagement, EEG power, or basic neural processing of speech between gaze conditions. Further, in Alpha and Beta bands, but not other bands, infants influenced adults more strongly than vice versa. This is the first demonstration that mutual direct gaze increases adult-infant neural coupling during social communication. Future research should explore the role of neural coupling in learning and other aspects of social behavior.
SIGNIFICANCE STATEMENT During infancy, the social context exerts powerful influences on learning. This context arises from dynamic interactions between social partners, yet all known neural infancy studies have only considered what occurs within one partner, the infant. Consequently, the contingency (temporal dependency) of infant’s neural activity on the adult’s and vice versa has never been measured. Yet, recent adult studies suggest that strong interpersonal neural contingency (coupling) predicts successful communication. Here, we report the first ever study to examine adult-infant neural coupling and characterize its causal architecture. We observed strong bidirectional adult-infant coupling which was significantly modulated by social gaze. These results are important because they challenge the current thinking about how social effects on early learning are understood and investigated.
