Interbrain coupling during language learning contributes to learning outcomes.

While knowledge and skill acquisition frequently occur in social interactions, the predominant focus of existing research remains centred on individual learning. Here, we investigate whether social interaction enhances language learning, and whether interbrain coupling changes across learning sessions. We utilized functional near-infrared spectroscopy to assess teacher-learner dyads engaging in a two-session training on a set of words and their plural inflections in a novel language. We compared a group trained with mutual communication with a noninteractive group, in which the learner could see and hear the teacher, but the teacher was unable to see or hear the learner (one-way mirror). Results revealed that compared to the No-interaction group, the Interaction group exhibited faster reaction times for vocabulary recognition and morphological inflections for the first session. The neuroimaging data revealed that interbrain coupling between the left inferior frontal gyrus (IFG) of the learner and the right IFG of the teacher positively predicted vocabulary accuracy in the first but not in the second session. The results collectively suggest that IFG interbrain coupling plays an essential role in the initial stages of learning, highlighting the significant impact of social interaction in enhancing learning, especially during the early phases of learning.