Brain responses reveal young infants' sensitivity to when a social partner follows their gaze

•Brain responses measured during social gaze interactions in 5-month-olds.•Infants' brains detect when a social partner follows their gaze.•Left prefrontal cortex involved in gaze following detection.•This brain sensitivity is critical for social learning.

Infants' ability to follow another person's eye gaze has been studied extensively and is considered to be an important and early emerging social cognitive skill. However, it is not known whether young infants detect when a social partner follows their gaze to an object. This sensitivity might help infants in soliciting information from others and serve as an important basis for social learning. In this study, we used functional near-infrared spectroscopy (fNIRS) to measure 5-month-old infants' frontal and temporal cortex responses during social interactions in which a social partner (virtual agent) either followed the infants' gaze to an object (congruent condition) or looked to an object that the infant had not looked at before (incongruent condition). The fNIRS data revealed that a region in the left prefrontal cortex showed an increased response when compared to baseline during the congruent condition but not during the incongruent condition, suggesting that infants are sensitive to when someone follows their gaze. The findings and their implications for the development of early social cognition are discussed in relation to what is known about the brain processes engaged by adults during these kinds of social interactions.