Interactive live fNIRS reveals engagement of the temporoparietal junction in response to social contingency in infants.

Live social interaction is the dominant form of human social activity, but it remains unclear if brain processing of live interactive social stimuli differs substantially from processing of non-interactive social stimuli, mainly because of technical difficulties measuring brain activity during natural social interactions. This distinction is particularly important during infancy considering the importance of real-life interactions for various forms of learning. To assess the impact of live social interaction accompanied by ostensive social signals on infant cortical processing, the present study measured the cortical activities of 6-8-month-old and 10-12-month-old infants using functional near-infrared spectroscopy under contingent and non-contingent conditions (appropriately timed versus delayed responsiveness). We found greater activation over the right temporoparietal junction region in response to contingent interactions relative to non-contingent interactions in 6-8-month-old and 10-12-month-old infants. Our study indicates a critical role of contingent responsiveness for differential processing of live interactive social stimuli.

Communicative hand-waving gestures facilitate object learning in preverbal infants.

The theory of natural pedagogy has proposed that infants can use ostensive signals, including eye contact, infant-directed speech, and contingency to learn from others. However, the role of bodily gestures, such as hand-waving, in social learning has been largely ignored. To address this gap in the literature, this study sought to determine whether 4-month-old infants exhibited a preference for horizontal or vertical (control) hand-waving gestures. We also examined whether horizontal hand-waving gestures followed by pointing facilitated the process of object learning in 9-month-old infants. Results showed that 4-month-old infants preferred horizontal hand-waving gestures to vertical hand-waving gestures, even when featural and contextual information were removed. Furthermore, horizontal hand-waving gestures induced identity encoding for cued objects, whereas vertical gestures did not. These findings highlight the role of communicative intent embedded in bodily movements and indicate that hand-waving can serve as a new type of ostensive signal.