The eyes have it: Neurobiological roots, developmental trajectories, and social significance of mutual gaze in early parent-infant interactions

Mutual Gaze (MG) plays a crucial role in early interactions, yet there is no clear terminological or conceptual definition, highlighting the need for consensus on its onset, development, and clinical implications. This review aims to provide new insights into the extent and the way in which MG develops during early mother-infant interactions, both typically and atypically, and how it may be associated with the child's future social, cognitive, and behavioral development. A PICO format was employed, a systematic literature search was conducted, and 28 studies were selected for this review. These studies varied in their terminological definitions of MG, sample sizes, participants' characteristics, and methodologies. Results were analyzed through thematic analysis, leading to the identification of four main themes: neuro-biological correlates of MG, developmental modifications in MG during the first year of life, the involvement of MG in social interaction, and MG in atypical neurodevelopment. The findings showed that MG is regulated by underlying neuro-biological processes, leading to specific behavioral and interactive modalities, which evolve over time during the first year and are positively associated with attentional control and emotional self-regulation. Additionally, MG exhibits distinct behavioral characteristics in certain neurodevelopmental conditions, such as preterm infants and those with Autism Spectrum Disorder (ASD), and may serve as a potential behavioral marker of ASD in infants older than 6 months, although further data are needed to draw definitive conclusions.